Series

Preconception health 1
Before the beginning: nutrition and lifestyle in the
preconception period and its importance for future health
Judith Stephenson, Nicola Heslehurst, Jennifer Hall, Danielle A J M Schoenaker, Jayne Hutchinson, Janet E Cade, Lucilla Poston, Geraldine Barrett,
Sarah R Crozier, Mary Barker, Kalyanaraman Kumaran, Chittaranjan S Yajnik, Janis Baird, Gita D Mishra

A woman who is healthy at the time of conception is more likely to have a successful pregnancy and a healthy child. Published Online
We reviewed published evidence and present new data from low-income, middle-income, and high-income countries April 16, 2018
http://dx.doi.org/10.1016/
on the timing and importance of preconception health for subsequent maternal and child health. We describe the S0140-6736(18)30311-8
extent to which pregnancy is planned, and whether planning is linked to preconception health behaviours.
This is the first in a Series of
Observational studies show strong links between health before pregnancy and maternal and child health outcomes, three papers about
with consequences that can extend across generations, but awareness of these links is not widespread. Poor nutrition preconception health
and obesity are rife among women of reproductive age, and differences between high-income and low-income Institute for Women’s Health,
countries have become less distinct, with typical diets falling far short of nutritional recommendations in both University College London,
London, UK
settings and especially among adolescents. Several studies show that micronutrient supplementation starting in
(Prof J Stephenson FFPH,
pregnancy can correct important maternal nutrient deficiencies, but effects on child health outcomes are disappointing. J Hall PhD, G Barrett PhD);
Other interventions to improve diet during pregnancy have had little effect on maternal and newborn health outcomes. Institute of Health and Society,
Comparatively few interventions have been made for preconception diet and lifestyle. Improvements in the Newcastle University,
Newcastle upon Tyne, UK
measurement of pregnancy planning have quantified the degree of pregnancy planning and suggest that it is more
(N Heslehurst PhD); School of
common than previously recognised. Planning for pregnancy is associated with a mixed pattern of health behaviours Public Health, University of
before conception. We propose novel definitions of the preconception period relating to embryo development and Queensland, Herston, QLD,
actions at individual or population level. A sharper focus on intervention before conception is needed to improve Australia
(D A J M Schoenaker PhD,
maternal and child health and reduce the growing burden of non-communicable diseases. Alongside continued Prof G D Mishra FAHMS);
efforts to reduce smoking, alcohol consumption, and obesity in the population, we call for heightened awareness of Nutritional Epidemiology
preconception health, particularly regarding diet and nutrition. Importantly, health professionals should be alerted to Group, School of Food Science
ways of identifying women who are planning a pregnancy. and Nutrition, University of

Introduction
Health of women around the time of conception, once Key messages
a neglected topic, is now a focus of increasing • Health before conception is strongly linked to the outcome of pregnancy; life-course
interest, reflected in several reports from national1,2 research pin-points the preconception period as crucial for health across generations.
and international health agencies.3,4 This Series on • The preconception period should be redefined according to (1) the biological
preconception health makes the case for preconception perspective—days to weeks before embryo development, (2) the individual
health as a key determinant of pregnancy success perspective—a conscious intention to conceive, typically weeks to months before
and next generation health, drawing on evidence across pregnancy occurs, and (3) the public health perspective—longer periods of months or
clinical, biological, social, and policy fields. In this years to address preconception risk factors, such as diet and obesity.
report, we follow three lines of enquiry. First, we review • Many women of reproductive age in low, middle, and high-income countries will not
the evidence linking preconception health, particularly be prepared nutritionally for pregnancy.
nutritional status, to pregnancy and birth outcomes, • Micronutrient supplementation started in pregnancy can correct important maternal
including analysis of the few cohort studies to have nutrient deficiencies, but it is not sufficient to fundamentally improve child health;
recruited women before pregnancy in low, middle, and dietary interventions in pregnancy can limit weight gain, but they are also insufficient
high-income countries (appendix),5–8 and we survey data in improving pregnancy outcomes.
on the nutrition of a nationally representative sample of • The preconception period presents a period of special opportunity for intervention;
women in a high-income country (the UK).9 Using these the rationale is based on lifecourse epidemiology, developmental (embryo)
data, we assess how well women are prepared, in health programming around the time of conception, maternal motivation, and
terms, for pregnancy. Second, we assess the extent to disappointment with interventions starting in pregnancy.
which intervention during pregnancy can mitigate the • Improved measurement shows that pregnancy planning is more common than
effect of preconception risk behaviours by reviewing previously recognised in low, middle, and high-income countries.
systematic reviews of dietary and lifestyle interventions • Identification of people contemplating pregnancy provides a window of opportunity
that started in pregnancy (appendix). Third, efforts to improve health before conception, while population-level initiatives to reduce the
to improve preconception health can be aimed at a determinants of preconception risks, such as obesity and smoking, irrespective of
population level, irrespective of any pregnancy planning, pregnancy planning, are essential to improve outcomes.
and can be targeted more specifically at women who are

www.thelancet.com Published online April 16, 2018 http://dx.doi.org/10.1016/S0140-6736(18)30311-8 1

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Leeds, Leeds, UK planning for pregnancy. We therefore review what is proportion of underweight women (BMI <18·5 kg/m²)
(J Hutchinson PhD, known about the extent of planning for pregnancy, decreased from 15% to 10%; South Asia had the highest
Prof J E Cade PhD); Department
including new data from a low-income country (Malawi) proportion of underweight women with an estimated 24%
of Women and Children’s
Health, King’s College London, on how to measure pregnancy planning.10 A host in 2014.20 Although the proportion of women who are
St Thomas’ Hospital, London, of social, medical, and environmental conditions underweight has decreased, the proportion of obese
UK (Prof L Poston PhD); Medical can influence pregnancy outcomes, including genetic women globally (BMI ≥30 kg/m²) has risen from 6% to
Research Council Lifecourse
disorders, pre-existing physical and mental health 15% from 1975 to 2014.20 In many low, middle, and high-
Epidemiology Unit, University
of Southampton, conditions, teratogens, and domestic abuse to name income countries, up to 50% of women are overweight
Southampton General a few. We recognise their importance, but review of or obese when they become pregnant.21,22 Obesity is
Hospital, Southampton, UK these conditions is outside the scope of this paper. associated with increased risk of most major adverse
(S R Crozier PhD, M Barker PhD,
Prof J Baird FFPH;
The importance of the father’s preconception health is maternal and perinatal outcomes: the inability to conceive,
K Kumaran FFPH); National addressed in the second Series paper whereas the third complications of pregnancy (eg, pre-eclampsia, gestational
Institute for Health Research Series paper reviews the targeting of intervention diabetes) and delivery (eg, macrosomia), congenital
Southampton Biomedical strategies to improve preconception health. anomalies, stillbirth, low birthweight, un­ successful
Research Centre, Southampton
General Hospital,
breastfeeding, and even maternal death.22–25 The global
Southampton, UK (Prof J Baird, Preconception risk factors in perspective increase in obesity among men (3–11% between 1975 and
M Barker); Epidemiology Life-course epidemiology provides a useful perspective 2014)20 is not irrelevant; paternal obesity has been linked to
Research Unit, CSI Holdsworth for examination of preconception factors and their effects impaired fertility by affecting sperm quality and quantity26
Memorial Hospital, Mysore,
Karnataka, India (K Kumaran);
on maternal, fetal, and child health by consideration of and is associated with increased chronic disease risk in
and Diabetes Unit, King the timing and duration of exposures and their potential offspring.27 The cumulative effect of maternal and paternal
Edward Memorial Hospital and long-term or latent effects.11 The relationship of exposures obesity on the risk of obesity in future generations has
Research Centre, Pune, to outcomes can be considered in terms of critical been proposed by several studies28 and causal pathways
Maharashtra, India
(Prof C S Yajnik MD)
periods, sensitive periods, and cumulative effects. For involving interaction between genetic, epigenetic, and
Correspondence to:
example, 2–3 months before and after conception is a environmental factors are emerging (see the second paper
Prof Judith Stephenson Institute critical period for optimising gamete function and early of this Series).
for Women’s Health, University placental development. In this period, folic acid Although the benefits of preconception weight loss
College London, London supplementation, for example, can reduce the risk of remain to be established through clinical trials, obser­
WC1E 6AU, UK
judith.stephenson@ucl.ac.uk
neural tube defects by as much as 70%.12,13 Other benefits vational studies indicate the probable effects of
of folic acid supplementation during periconception preconception weight loss on pregnancy outcomes.
See Online for appendix might include decreased risk of pre-eclampsia, In a population-based study29 in Canada including
miscarriage, low birthweight, small for gestational age 226 958 women (64% normal weight, 20% overweight,
birth, stillbirth, neonatal death, and autism in children.14–16 and 12% obese) with singleton pregnancies, a 10%
The consequences of maternofetal iron deficiency also fit lower preconception BMI was associated with clinically
a critical period model in which repletion after an meaningful risk reduction in pre-eclampsia, gestational
undetermined timepoint does not rectify structural diabetes, preterm delivery, macrosomia, and stillbirth.
impairments to developing brain structures. In Also, women undergoing bariatric surgery at least
experimental rodent models, dietary restriction of iron 2 years before conception have considerably lower risk
from the beginning of gestation can induce a of gestational diabetes, hypertensive disorders,
40–50% decrease in brain iron 10 days after birth17 and and large-for-gestational-age neonates than women of
preconception zinc deficiency compromises fetal and similar BMI who had no bariatric surgery (although this
placental growth and neural tube closure.18 Adolescence is partially offset by a higher risk of neonates who were
might represent a particularly sensitive period as small for their gestational age).30–32 Higher amounts of
unhealthy life-style behaviours—eg, smoking, poor diet, preconception physical activity were associated with
and eating disorders—often originate in the teenage lower risk of gestational diabetes (odds ratio [OR] 0·45,
years. These preconception risk factors can set patterns 95% CI 0·28–0.75 in seven cohorts, 34 929 pregnancies)33
that have a cumulative effect on health into adulthood and pre-eclampsia (relative risk [RR] 0·65, 95% CI
and for future generations, as shown by mounting 0·47–0·89, in five studies, 10 317 pregnancies).34 Walking
evidence of the long-term effects of poor maternal at a brisk pace for 4 h or more per week before pregnancy
nutrition and obesity for the child.19 was also associated with lower risk of gestational
diabetes.35 The success of a life-style intervention in
Maternal body composition, nutrition, and life-style reducing weight retention postpartum36 shows that
factors preparation for health in the next pregnancy can begin
Substantial risks for maternal and child health are straight after the previous pregnancy.
associated with mothers who are underweight or Diet and nutrition before pregnancy might modify
overweight. An analysis of adult body-mass index (BMI) maternal and perinatal outcomes via effects on BMI
in 200 countries from 1975 to 2014 with over 19 million (discussed previously) or other nutritional factors,
participants found that the age-standardised global including micronutrient deficiencies. WHO estimates

2 www.thelancet.com Published online April 16, 2018 http://dx.doi.org/10.1016/S0140-6736(18)30311-8

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LNRI* Non-pregnant women of reproductive age (by age at survey) p value†

Total Age 18–25 years Age 26–30 years Age 31–35 years Age 36–42 years
(N=509) (n=156, 32%) (n=79, 19%) (n=102, 18%) (n=172, 31%)
Dietary and lifestyle characteristics
BMI (SD) ·· 26·0 (6·7) 25·1 (5·4) 25·3 (5·2) 26·7 (6·2) 27·7 (6·3) 0·1
Overweight or obese ·· 49% (43–54) 41% (32–51) 40% (29–53) 49% (38–60) 62% (54–70) 0·004
Fruit and vegetable consumption ·· 77% (73–81) 91% (84,95) 70% (56–80) 70% (60–79) 72% (63–79) 0·003
(<5 serves per day)
Current smoker ·· 26% (22–30) 33% (25–43) 22% (14–33) 20% (13–29) 24% (17–31) 0·2
High risk alcohol intake‡ ·· 22% (18–26) 28% (19–38) 16% (9–26) 12% (7–20) 25% (19–33) 0·03
Percentage with diet-only intakes below LRNIs
Vitamins
Vitamin A 250 µg/day 7% (5–9) 12% (8–19) 5% (5–14) 2% (1–4) 5% (3–10) 0·002
Vitamin B12 1·0 µg/day 2% (1–3) 4% (2–8) 0 1% (0–3) 1% (0–6) 0·1
Folate 100 µg/day 4% (3–7) 8% (4–13) 1% (0–6) 0% (0–2) 5% (2–9) 0·003
Riboflavin 0·8 mg/day 14% (11–18) 22% (15–32) 11% (6–20) 9% (5–15) 11% (7–17) 0·03
Minerals
Calcium 400 mg/day§ 9% (7–12) 13% (9–20) 6% (3–14) 6% (3–12) 9% (5–14) 0·2
Iodine 70 µg/day 15% (11–19) 22% (15–31) 13% (7–23) 7% (4–14) 11% (7–18) 0·02
Iron 8·0 mg/day 30% (25–34) 38% (29–47) 26% (17–37) 23% (16–32) 27% (21–35) 0·09
Potassium 2000 mg/day 29% (25–34) 41% (32–51) 26% (17–38) 19% (12–28) 25% (19–33) 0·003
Selenium 40 µg/day 51% (47–56) 57% (47–66) 37% (26–49) 52% (42–62) 54% (46–61) 0·08
Zinc 4 mg/day 4% (3–7) 6% (3–11) 3% (1–9) 4% (2–9) 4% (2–9) 0·7

Data are % (95% CI). Means (SD) and percentages (95%CIs) are weighted to provide nationally representative results. Data are from the UK National diet and Nutrition
Survey Rolling Program (NDNS RP) (2008/2012) years 1–4.9 BMI=body-mass index. LRNI=lower reference nutrient intake. *Micronutrient LRNIs are those recommended for
the UK in COMA, 1991.42 †p values for comparison across age groups. ‡Over six units of alcohol in one drinking occasion in the previous 7 days. §LRNI calcium is different for
age 18 years (450 mg/day).

Table 1: Dietary intake and lifestyle characteristics of women of reproductive age in the UK National Diet and Nutrition Survey

that around 2 billion people are deficient in micro­ RNI daily recommendations for iodine and 96% of
nutrients, with women being at particular risk because women of reproductive age had intake of iron and folate
of menstruation and the high metabolic demands of below daily recommendations for pregnancy (data not
pregnancy.37 Globally, maternal undernutrition and shown). Adequate folate concentration in pregnancy (red
its consequences, including maternal vitamin A and blood cell folate concentration above 906 nmol/L) for
zinc deficiency, fetal growth restriction, childhood prevention of neural tube defects is hard to achieve
stunting and wasting, together with suboptimal through diet alone.43 Folic acid supplements or fortified
breastfeeding, is estimated to account for 3·1 million foods are effective alternatives. In a cohort of over
child deaths annually, and 45% of all child deaths in 1·5 million women in China, folic acid supplementation
2011.38 A comprehensive review39 of nutrition among 3 months before pregnancy (n=1 182 967) was associated
adolescent girls and women of reproductive age in low- with significantly lower risk of low birthweight (OR 0·74,
income and middle-income countries (LMICs) 95% CI 0·71–0·78), miscarriage (OR 0·53, 0·52–0·54),
concluded that despite the reduction in prevalence of stillbirth (OR 0·70, 0·64–0·77), and neonatal mortality
underweight mothers, dietary deficiencies (including (OR 0·70, 0·63–0·78) than in women who did not take
iron, vitamin A, iodine, zinc, and calcium) remain folic acid before pregnancy (n=352 009).16 In several
prevalent.39 A typical diet in high-income countries, countries (including Canada, Chile, Oman, Jordan, Costa
characterised by a high intake of red meat, refined Rica, South Africa, USA) a decrease in neural tube defects
grains, refined sugars, and high-fat dairy, is also lacking has been observed following mandatory folic acid
in several important nutrients (including magnesium, fortification, typically of wheat flour or cereal grain
iodine, calcium, and vitamin D).40,41 products, in the country or region.13 A mild degree of
Our analysis in the UK shows that many women of iodine deficiency in pregnancy has been linked to lower
reproductive age will not be nutritionally prepared for intelligence quotients in offspring,40 although the balance
pregnancy, since they do not meet even the lower between the benefit and risk from iodine supplementation
reference nutrient intake (RNI) amounts, which applies before or during pregnancy remains unclear.44
especially to young women and mineral intake (table 1). Cohort studies have suggested that dietary patterns
77% of women aged 18–25 years had dietary intakes below up to 3 years before pregnancy, characterised by high

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All women* Preconception characteristics of women who gave birth during the study† p value‡
Survey 1 Survey 7 Age at first birth
(age 18–23 (age 37–42
years [n=7047]) years
[n=6981])
Age 18–25 years Age 26–30 years Age 31–35 years Age 36–42 years
(n=544, 17·4%) (n=1293, 41·5%) (n=1024, 32·8%) (n=257, 8·2%)
Mean BMI (SD) 22·8 (4·2) 26·8 (6·4) 23·4 (4·8) 23·9 (4·4) 24·3 (4·5) 25·2 (5·6) <0·0001
Overweight or obese 1340 (21·0%) 3223 (52·1%) 100 (27·2%) 342 (30·6%) 318 (34·0%) 94 (39·7%) 0·005
Fruit and vegetable 5861 (91·9%) 5659 (91·0%) .. 806 (91·9%) 533 (92·5%) 115 (86·5%) 0·13
consumption (<5 serves per day)
Physical activity (<30 min/day) 1908 (37·7%) 2217 (43·3%) 249 (52·1%) 451 (38·8%) 318 (34·4%) 95 (41·1%) <0·0001
Current smoker 1830 (27·9%) 685 (10·5%) 147 (28·0%) 227 (18·6%) 131 (13·4%) 35 (14·3%) <0·0001
High risk alcohol intake§ 348 (5·1%) 459 (6·9%) 17 (3·2%) 45 (3·6%) 49 (4·9%) 18 (7·1%) 0·008

Data are mean (SD) or n (%). The Australian Longitudinal Study on Women’s Health (ALSWH) is a population-based study of women born in 1973–78 who have been
surveyed every 3–4 years since 1996 (age 18–23 years).5 BMI=body-mass index. *All women including women who have not given birth. †Preconception characteristics
shown in the table were reported at the survey before the first pregnancy (up to 3 years). ‡p values for comparison across age groups. §Three or more standard drinks
(10 g alcohol) on 5 or more days per week.

Table 2: Dietary intake and lifestyle characteristics of women of reproductive age in the Australian Longitudinal Study on Women’s Health

intake of fruit, vegetables, legumes, nuts, and fish, and conception could be beneficial. However, as with all
low intake of red and processed meat, are associated with preconception risk factors the scope for action at the
reduced risk of gestational diabetes,45–48 hypertensive individual level is limited by unplanned pregnancy,
disorders of pregnancy,49–51 and preterm birth.52 Since few which in turn highlights the importance of cost-effective
people will plan a pregnancy 3 years in advance, this public health action (eg, minimum pricing of alcohol and
highlights the need for population-level interventions. In smoke-free legislation) to reduce risk behaviours in the
the UK and Australia, more than nine of ten young whole population, with additional benefit for women
women reported consuming fewer than five fruit and whose pregnancies are unplanned.
vegetable portions daily (table 1 and table 2). As the diet Since women are more likely to engage with health
of a young child is determined largely by the mother, this services once they are pregnant than beforehand, we
aspect has important implications for future child health. considered whether birth outcomes can be improved
Evidence for the effect of maternal smoking on health through intervention during pregnancy to redress poor
outcomes (including pregnancy loss, intrauterine growth dietary patterns that were present before conception.
restriction, and low birthweight) comes largely from In high-income countries, the obesity epidemic has
studies initiated during, rather than before, pregnancy.53,54 dominated efforts to improve pregnancy outcomes. Our
Although no trials have been published that show overview identified 20 systematic reviews of antenatal
reduction in smoking before conception improves these interventions with a dietary component, six confined to
outcomes, indirect evidence of the effect at population overweight or obese women (figure 1; appendix). These
level comes from introduction of smoke-free legislation reviews, mainly of trials from high-income countries,
in different countries, which has been associated provide high quality consistent evidence that dietary
with substantial reductions in preterm births (–10·4%, interventions (with or without exercise) during
95% CI –18·8 to –2·0, from four cohort studies with pregnancy can reduce gestational weight gain; however,
1 366 862 pregnancies).55 Maternal alcohol consumption an individual patient data (IPD) meta-analysis58 of
can result in a range of fetal alcohol spectrum disorders 36 randomised controlled trials with 12 526 women of
that result in physical, behavioural, and learning mixed BMI found an average reduction in gestational
difficulties.56 Although discussion of alcohol consumption weight gain of only 0·7 kg (95% CI –0·92 to –0·48).
of any amount being safe during pregnancy is Some reviews59–61 also reported that dietary intervention
controversial, there is widespread public awareness that during pregnancy, with increased consumption of fibre,
avoidance of both smoking and alcohol during pregnancy protein, fruit, and vegetables, led to reduction in dietary
is important for health. Caffeine consumption during fat and energy intake. High quality trials published after
pregnancy has been associated with a reduction in these systematic reviews show similar effects on dietary
birthweight of a similar proportion to that caused by behaviours. The LIMIT trial62 in Australia showed that a
alcohol, with a significant trend for a greater reduction diet and physical activity intervention delivered to
in birthweight with higher caffeine intake.57 This overweight and obese women increased their
relationship was consistent across all three trimesters, consumption of fruit, vegetables, legumes, fibre, and
suggesting that cutting back on caffeine before micronutrients, and reduced their energy intake

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A Number of Weighted mean B Number of Relative risk

included studies difference, kg (95% CI) included studies (95% CI)
Gestational weight gain Gestational diabetes mellitus
Diet interventions
Diet interventions
Dodd et al (2010) 4 –3·10 (–8·32 to 2·13)
Quinlivan et al (2011) 4 –6·46 (–7·55 to –5·37) Dodd et al (2010) 3 0·57 (0·30 to 1·08)
Tanentsapf et al (2011) 10 –1·92 (–3·65 to –0·19)
Tanentsapf et al (2011) 6 0·74 (0·52 to 1·06)
Thangaratinam et al (2012a) 10 –3·84 (–5·22 to –2·45)
Thangaratinam et al (2012b) 9 –3·36 (–4·73 to –1·99) Thangaratinam et al (2012a) 3 0·39 (0·23 to 0·69)
Diet and physical activity interventions
Agha et al (2014) Thangaratinam et al (2012b) 2 0·52 (0·27 to 1·03)
14 –1·66 (–3·12 to –0·21)
Campbell et al (2011) 5 –0·28 (–0·64 to –0·09)
Gardner et al (2011) 12 –1·19 (–1·74 to –0·65)
Hill et al (2013) 22 –1·54 (–1·86 to –1·21) Diet and physical activity interventions
Muktabhant et al (2015) (PA counselling) 11 –0·71 (–1·34 to –0·08) Thangaratinam et al (2012a) 6 1·18 (0·78 to 1·77)
Muktabhant et al (2015) (PA supervised) 3 –1·31 (–3·00 to 0·37)
Oteng-Ntim et al (2012) 10 –2·20 (–2·86 to –1·57) Thangaratinam et al (2012b) 4 0·96 (0·49 to 1·86)
Thangaratinam et al (2012a) 10 –1·06 (–1·67 to –0·46) ScHARR (2009) 3 0·44 (0·12 to 1·54)
Thangaratinam et al (2012b) 6 –0·57 (–1·60 to 0·65)
–8·32 kg 0 kg 8·32 kg 0 1 2

C Number of Relative risk D Number of Relative risk

included studies (95% CI) included studies (95% CI)
Pre-eclampsia Preterm birth
Diet interventions Diet interventions
Dodd et al (2010) 5 0·80 (0·49 to 1·31) Dodd et al (2010) 2 0·58 (0·19 to 1·70)
Muktabhant et al (2015) 4 0·90 (0·54 to 1·48) Muktabhant et al (2015) (Diet: general) 3 0·67 (0·26 to 1·73)
Tanentsapf et al (2011) 6 0·78 (0·58 to 1·06) Tanentsapf et al (2011) 4 0·83 (0·51 to 1·34)
Thangaratinam et al (2012a) 6 0·67 (0·53 to 0·85) Thangaratinam et al (2012b) 4 0·68 (0·48 to 0·96)
Muktabhant et al (2015) (Diet: Low GL) 2 0·33 (0·11 to 1·02)
Diet and physical activity interventions Diet and physical activity interventions
Thangaratinam et al (2012b) 3 1·48 (0·56 to 3·94) Thangaratinam et al (2012a) 4 0·90 (0·55 to 1·47)
Thangaratinam et al (2012a) 4 1·16 (0·70 to 1·90) Thangaratinam et al (2012b) 4 1·02 (0·47 to 2.21)
Muktabhant et al (2015) 7 1·06 (0·79 to 1·43) Muktabhant et al (2015) 7 0·94 (0·57 to 1·55)

0 1 2 3 4 0 1 2 3
Favours intervention Favours controls
E Number of Relative risk
included studies (95% CI)
High birthweight
Diet interventions
Dodd et al (2010)* 3 2·02 (0·84 to 4·86)
Muktabhant et al (2015) (diet: general)† 2 1·81 (0·88 to 3·72)
Muktabhant et al (2015) (diet: low GL)† 4 0·96 (0·77 to 1·20)
Tanentsapf et al (2011)† 6 0·94 (0·62 to 1·35)
Thangaratinam et al (2012a)* 5 0·78 (0·51 to 1·19)
Diet and physical activity interventions
Muktabhant et al (2015) (PA counselling)† 9 0·85 (0·73 to 1·00)
Muktabhant et al (2015) (PA supervised)† 3 1·02 (0·71 to 1·46)
Thangaratinam et al (2012a)* 9 1·05 (0·79 to 1·40)
Thangaratinam et al (2012b)* 5 0·75 (0·41 to 1·38)

0 1 2 3
Favours intervention Favours controls

Figure 1: Meta-analyses of the effect of dietary behaviour change interventions (with or without physical activity elements) in pregnant women
Effect estimates of dietary behaviour change interventions (with or without physical activity components) in pregnant women. Each estimate is from a systematic review with meta-analysis.
A summary estimate has not been generated because some intervention studies are included in more than one meta-analysis. GL=glycaemic load. PA=Physical activity.

sourced from saturated fat. The UPBEAT trial63 in the longer-term benefits, these interventions have had no
UK also showed a reduction in the consumption of significant effect on common adverse pregnancy
processed foods and snack foods among obese women outcomes, including gestational diabetes, pre-
after diet and physical activity intervention. Both trials eclampsia, large for gestational age, or preterm births,
showed dietary behaviour change at 28 weeks and in women of mixed BMI or in obese women (figure 1);
36 weeks gestation, and the UPBEAT trial reported however, the IPD meta-analysis58 reported a
reduced infant adiposity 6 months postpartum.64 9% reduction in caesarean section in women of all BMIs
Although improved health behaviours and weight gain (OR 0·91, 95% CI 0·83–0·99). Because attempts to
restriction should not be ignored due to the potential improve outcomes in obese women with the use of

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Eating 5-a-day
100 Overweight or obese
Drinking alcohol
Taking folic supplement
90 Smoking

80

70
Proportion of young women (%)

60

50

40

30

20

10

0
–36 –24 –12 –3 –2 –1 0
(or decision for pregnancy) (conception)

Time before conception (months)

Figure 2: Challenges of improving preconception health

Typical levels of each preconception behaviour in young women in high-income countries (solid lines) and optimal behaviours before conception (dashed lines).

insulin-sensitising drugs have also been unsuccessful,65,66 high-income lifestyles that foster obesity, whereas
attention is increasingly focused on the improvement populations in high-income countries already dominated
of diet and prevention or reverse of obesity in the by obesity commonly have poor nutrition and specific
preconception period. Given the substantial time micronutrient deficiencies that go unrecognised until
needed to reach a healthy weight, early intervention at a pregnancy. Iron deficiency anaemia, for example, is
population level is vital to reduce obesity-related the most common deficiency globally affecting around
outcomes in pregnancy. 2 billion people and 30–50% of pregnant women,73
In LMICs, antenatal dietary interventions have including young women in high-income countries.74
generally focused on the problem of calorific and Although iron supplementation in pregnancy reduces
nutrient deprivation. A single trial67 in Mumbai found iron deficiency anaemia and improves haemoglobin
that women who ate a daily snack containing leafy green concentrations at term, other benefits seem limited to a
vegetables, fruit, and milk before and during pregnancy reduction in low birthweight.75 Vitamin D deficiency,
had reduced prevalence of gestational diabetes (7·3% increasingly common among pregnant women in high-
in the intervention group compared with 12·4% in income countries, can lead to bone mineral deficiency in
the control group). Several studies68,69 have exam­ the developing child and has been implicated in gestational
ined the effect of antenatal multiple micronutrient diabetes, pre-eclampsia, low birthweight, and preterm
supplementation on a range of health outcomes in high- birth but with less certainty.76 A subsequent trial77 of
risk populations in LMICs, but the findings are cholecalciferol supplementation during pregnancy showed
disappointing. Systematic reviews70,71 of trials of multiple that most women became vitamin D replete, but infant
micronutrient supplementation during pregnancy, in­ bone mineral content was not increased overall.77 Further
cluding over 88 000 women, have consistently shown studies, such as the SPRING trial78 of cholecalciferol
modest effects on increasing birthweight when com­ supplementation during pregnancy, are awaited.
pared with control groups receiving iron and folic In summary, interventions to improve diet in pregnancy
supplementation only; however, these reviews have lead to modest reductions in gestational weight gain, but
shown no improvement in childhood survival, growth, (with few exceptions)64 they have not improved important
body composition, blood pressure, or respiratory or maternal or newborn health outcomes. Micronutrient
cognitive outcomes when comparing the intervention supplementation starting in pregnancy can correct
and control groups. important maternal nutrient deficiencies with modest
Distinctions between high-income countries and LMICs effects on increasing birthweight, but no subsequent
have become blurred because many LMICs have had improvement in child health outcomes. Explanations
a demographic and obstetric transition72 coupled with might include starting interventions after early critical

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ALSWH cohort SWS cohort

Using contraception or Trying for Not using Not planning Unintended Intended Planning a
no male sexual partner pregnancy contraception pregnancy and pregnancy pregnancy pregnancy but
(n=6256, 77%)* (n=536, 7%)* (n=1285, 15·9%)* not pregnant (n=301, 2%) (n=584, 5%) not pregnant
(n=9932, 80%) (n=1623, 13%)
Smoking (yes vs no) 1·00 (ref) 0·84 (0·76–0·93) 1·09 (1·01–1·18) 1·00 (ref) 1·15 (1·00–1·33) 0·72 (0·61–0·83) 0·89 (0·82–0·96)
Alcohol consumption (yes vs no) 1·00 (ref) 0·70 (0·56–0·87) 0·91 (0·77–1·09) 1·00 (ref) 1·01 (0·98–1·05) 1·03 (1·01–1·06) 0·99 (0·97–1·00)
Fruit and vegetable consumption 1·00 (ref) 1·01 (0·99–1·03) 0·97 (0·96–0·99) 1·00 (ref) 1·05 (0·94–1·17) 0·94 (0·85–1·03) 0·97 (0·92–1·03)
(<5 vs ≥5 serves per day)
Physical activity (<30 vs ≥30 min/day) 1·00 (ref) 1·06 (1·01–1·11) 1·14 (1·09–1·18) ·· ·· ·· ··
Body-mass index (≥25 vs <25 kg/m²) 1·00 (ref) 1·05 (1·00–1·10) 1·16 (1·12–1·21) 1·00 (ref) 0·98 (0·85–1·13) 1·10 (1·00–1·21) 1·13 (1·07–1·20)
Caffeine consumption (>300 mg caffeine per day) ·· ·· ·· 1·00 (ref) 1·15 (1·01–1·31) 0·89 (0·79–0·99) 0·94 (0·88–1·01)

Data are relative risk (95% CI) using Poisson regression with robust variance, adjusted for maternal age, level of educational attainment and parity. The Australian Longitudinal Study on Women’s Health (ALSWH)
is a population-based study of women born in 1973–78 who have been surveyed every 3–4 years since 1996 (age 18–23 years).5 The Southampton Women’s Survey (SWS) recruited 12 583 non-pregnant women
(20–34 years) between 1998 and 2002.6,7 When not pregnant, women in the SWS were asked whether they anticipated trying for a baby within the following year. Data about pregnancy within a year were then
used to define four groups of women: not planning pregnancy and not pregnant, unintended pregnancy, intended pregnancy, and planning a pregnancy but not pregnant. *N was taken from Survey 3, which was
the first survey where women were asked about pregnancy intention.

Table 3: Relative risk of diet and lifestyle behaviours according to pregnancy intention in the ALSWH and the SWS.

periods of fetal development or inadequate implemen­ fertilisation occurs, and the developing embryo forms.
tation, dose, or adherence within this timeframe to These events are the most sensitive to environmental
achieve substantial biological influence. In keeping with factors, such as the availability of macronutrients and
this hypothesis, one of the few supplementation trials79 micronutrients, or exposure to smoking, alcohol, drugs,
starting before conception found no effect on birthweight or other teratogens. For prevention of neural tube defects,
unless it was provided at least 3 months before conception a minimum of 4–6 weeks folic acid supplementation
and to women who were not underweight. To ex­ is required to reach adequate concentrations before
plore adherence to preconception supplementation, we neurulation begins 3 weeks after conception.13
analysed data from the Pune Rural Intervention in Young In relation to an individual, the preconception period
Adolescents (PRIYA)8 study. PRIYA is a randomised starts whenever a woman or couple decides they want to
community-based trial of cyanocobalamin (vitamin B) have a baby because the time to conception is unknown.
supplementation given to men and to young women Since about a third of fertile couples having regular
before pregnancy. Adherence, assessed by pill counts, in sex without contraception will conceive within one
this non-pregnant trial population was consistently high month,80,81 optimising nutrition, including folic acid
at around 80%. Although every effort should be made supplementation, should coincide with the decision to
to correct micronutrient deficiencies in women once become pregnant. The preconception period might reflect
pregnant, there is a growing consensus that the greatest the time required by individuals to achieve desired health
gain will be achieved through a life-course approach or outcomes in preparation for pregnancy, such as 6 or more
continuum of improved nutrition in children, adolescents, months to attain a healthy BMI. Maternal motivation to
and young women contemplating pregnancy (see the improve health at this stage can be strong. In a pilot study,83
third paper of this Series). 65% of obese women attending a family planning clinic to
have their contraceptive implant or uterine device removed
Defining the preconception period to become pregnant were willing to improve their
The preconception period is often defined as the preconception health by deferring removal of contraception
3 months before conception, probably because this is for 6 months while they followed an intensive weight loss
the average time to conception for fertile couples.80,81 plan. From a public health perspective, the preconception
However, a time period before conception can only be period can relate to a sensitive phase in the lifecourse, such
identified after a woman has become pregnant. Some as adolescence, when health behaviours affecting diet,
definitions avoid this problem, for instance “a minimum exercise, and obesity, along with smoking and drinking,
of one year prior to the initiation of any unprotected become established before the first pregnancy.
sexual intercourse that could possibly result in a These perspectives can be combined into a conceptual
pregnancy”,82 but cannot be applied practically. framework of the preconception period (figure 2).
We therefore propose three new definitions or Benefits that can be achieved fairly rapidly, such as
perspectives that relate to embryo development or point adequate folate concentrations, are indicated at 3 months
to interventions at an individual or population level. before conception or whenever an individual first
From a biological perspective, a critical period spans intends to become pregnant. Conversely, substantial
the weeks around conception when gametes mature, weight loss takes months or years to achieve, whereas

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 Series

DHS1 compared with antenatal LMUP score DHS12 compared with antenatal LMUP score Southampton Women’s Study,6,7 education had a signifi­
Intended cant effect on the association between pregnancy status
120
Mistimed and fruit and vegetable intake before pregnancy. Women
Unwanted
educated beyond 16 years of age who were intentionally
pregnant were more likely to report eating five portions of
fruit and vegetables a day (65%) than those who did not
80 become pregnant and were not planning to (57%); whereas
no differences were seen between the same pregnancy
Frequency (n)

intention groups in women who were educated up to

16 years of age only (46% in the intended pregnancy group
vs 46% in the group with no pregnancy). This result
40 suggests that more educated women might improve
their diet once a decision has been made for preg­
nancy but less educated women do not, highlighting the
effect of disadvantage on the ability of women to change
their behaviours.
0
0 1 2 3 4 5 6 7 8 9 10 11 12 0 1 2 3 4 5 6 7 8 9 10 11 12 Although some studies85,86 suggest that awareness of
Score Score preconception health and care is low, pregnancy planning
appears relatively common, indicating a missed and
Figure 3: Comparison of women’s antenatal LMUP score
unexploited opportunity for intervention.87,88 Pregnancy
Responses to the DHS question completed at least one month (DHS1) and at least 12 months (DHS12) after birth.
DHS=Demographic and Health Survey. LMUP=London Measure of Unplanned Pregnancy. planning has usually been estimated in surveys, either by
a single question (eg, Did you plan your pregnancy?) or by
the length of time to establish new dietary patterns is more detailed questioning to probe (variously) intentions,
highly variable. Together, these findings point to the reactions to pregnancy, timing of pregnancy, and family
scale of the challenge in improving preconception size desires. The most influential survey the US National
health, with vast room for improvement particularly in Survey of Family Growth87 categorises pregnancy as
nutritional status and the need for intervention strategies intended, mistimed, or unwanted—terms now widely
at the population level to support action at the individual adopted and included in the worldwide Demographic and
level (figure 2). Health Surveys (DHS).89 A combination of all survey
information has estimated that 60% of the 213 million
Pregnancy planning for preconception health pregnancies worldwide in 2012 were intended.88
Compelling evidence for early developmental program­ In the past 20 years, the growing complexity of
ming, along with the disappointment from micronutrient family formation patterns worldwide, awareness of the
supplements and dietary interventions in pregnancy, is need to accommodate women’s ambivalence, and the
shifting attention to the challenge of intervening before contribution of psychometric methods to measurement
conception. Awareness of the importance of health before development have indicated the need for a more
pregnancy, some level of pregnancy planning, and up­ sophisticated measurement of pregnancy planning. The
take of interventions before conception are distinct but London Measure of Unplanned Pregnancy (LMUP)90 has
related requirements for improving preconception health. been widely used, with nine validated language versions
Qualitative research84 has identified three groups: women across seven countries and more in progress.91–97
with high levels of pregnancy planning who take up Six questions produce a score (0–12), with higher scores
interventions, women who plan but describe themselves indicating a more planned pregnancy. Use of the LMUP
as having poor awareness of preconception actions, and has shown that pregnancy planning at various levels
women for whom the preconception period has little of intensity is globally common particularly among
meaning. Different preconception care approaches are pregnancies leading to birth.10,85,91–96,98,99 By providing a finer
likely to be needed for each group. gradation of pregnancy planning the LMUP is
Our analysis of new data from two preconception cohort more reliable than previous tools, opening the door to
studies5–7 shows mixed health behaviours reported in improved prediction of health outcomes associated
relation to pregnancy planning. Women trying for preg­ with pregnancy intention. Despite the availability of this
nancy when compared with those who were using superior tool, the global standard remains the DHS, in
contraception or not planning to become pregnant within which women are asked, “When you got pregnant, did
the next year, were less likely to report smoking or drinking you want to get pregnant at the time?” Women who
alcohol, reported lower amounts of caffeine consumption, respond yes are categorised as intended pregnancies,
had a higher BMI, reported lower amounts of physical those who respond no are asked “Did you want to have a
activity, but had similar fruit and vegetable intake (table 3). baby later on or did you not want any (more) children?”
These associations were robust to adjustment for mat­ An answer of later defines the pregnancy as mistimed and
ernal educational attainment, age, and parity. In the no more as unwanted.

8 www.thelancet.com Published online April 16, 2018 http://dx.doi.org/10.1016/S0140-6736(18)30311-8

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In a cohort study of pregnant women in Malawi,10 we appear to occur too late to fundamentally improve child
compared the LMUP scores reported during pregnancy health outcomes.
with the DHS categorisation reported up to 16 months Novel definitions of the preconception period that relate
after. 45% of women scored ten or more on the LMUP to embryo development or to opportunities for inter­
antenatally, showing that pregnancy planning is a vention might be useful. Action to improve conditions
relevant concept in a rural, low-income setting. The around the crucial time of conception requires a more
estimated prevalence of intended pregnancies was higher systematic approach to identify women planning a
with the use of the postnatal DHS question (69%, 95% CI pregnancy, and efforts are underway. A healthy weight
65–73) than the antenatal LMUP (40%, 95% CI 36–44) can take longer to achieve than dietary changes and
in the same group of 623 women at 1-year follow-up should ideally become established during the sensitive
(figure 3). Previous studies have found that the same period of adolescence when most women will not
birth is reported as more intended as time passes,100 but be planning pregnancy; this intervention requires a
these are the first data to document that this shift occurs population-level approach. Generally, however, a degree
within the first year postnatally. This result suggests a of pregnancy planning is common in LMICs and high-
need for antenatal surveillance of pregnancy intention income countries, offering considerable scope for
that could improve accuracy in assessing the scale of intervention before pregnancy. Pregnancy planning is
unplanned pregnancies and provide an opportunity to associated with an inconsistent pattern of reported health
act antenatally to mitigate the adverse effects for the behaviours potentially due to low awareness of the
mother and child. A measure, such as the LMUP, would importance of health before pregnancy and possible
also be sensitive enough to monitor changes in the rate actions to take. To have a substantial impact on
of unplanned pregnancy over time and across popu­ preconception health, a dual strategy is needed that
lation subgroups. Most initiatives to reduce unplanned improves nutritional status across the life-course and
pregnancy, such as Family Planning 2020,101 rely on particularly during reproductive ages, while targeting all
uptake of contraception as a proxy measure of effect, women who are thinking of conceiving. How this strategy
whereas the LMUP could provide a direct measure of the might be achieved is considered in the third paper of this
desired outcome. Series, which focuses on preconception care.
The frequency of pregnancy planning identified by Contributors
the LMUP in low, middle, and high-income countries DJAMS reviewed reports on preconception risk factors. NH reviewed
suggests considerable scope for intervention before reports on interventions in pregnancy. Further data analysis was provided
by SRC, JHa, GDM, KK, CY, and JHu. All authors contributed to
pregnancy; the challenge is to identify women who are successive drafts and approved the final version.
planning a pregnancy. Asking a woman of reproductive
Declaration of interests
age, “How many (more) children would you like to have JB and MB report receiving research funding from Danone Nutricia
and when?”, is being promoted,102 but the question is likely Early Life Nutrition. JB is evaluating the effect of changes within Iceland
to have limited predictive validity. More nuanced measures Foods Ltd stores on the diets of women. No research funding is received
from Iceland Foods Ltd. All other authors declare no competing
that capture ambivalent intentions are required—eg, the
interests.
Desire to Avoid Pregnancy (DAP) scale that is in
Acknowledgments
development.103 Robust measures, such as the LMUP and
The idea for this Series was conceived by JS and developed during a 4-day
DAP, are opening up a largely unexplored area of research symposium, led by MB and JS and funded by The Rank Prize Funds, on
into how people plan and prepare for pregnancy, the Developmental Programming for Human Disease: Preconception
associated effects on health, and how health professionals Nutrition and Lifelong Health in Grasmere, UK, in February, 2016.
We thank the Australian Government Department of Health for funding
can identify individuals planning a pregnancy. the Australian Longitudinal Study on Women’s Health, Kate Best for
producing the Forest plots, and Andrew Copp for advice on folate
Summary concentrations and the developing fetus. LP is supported by Tommy’s
A consistent picture is emerging of the importance of Charity, London, UK, and the National Institute for Health Research
Biomedical Research Centre at King’s College London, and Guys and
maternal health before conception and the key risk factors St Thomas’ National Health Service (NHS) Foundation Trust, London,
for adverse birth outcomes, one that blurs previous UK. JS is supported by Central and North West London NHS Foundation
distinctions between low, middle, and high-income Trust, London, UK.
countries. A life-course model of critical periods, sensitive References
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