1284766 JFM Journal of Feline Medicine and Surgery

Original Article

Journal of Feline Medicine and Surgery

Feline dystocia and kitten mortality 1­–10

© The Author(s) 2024
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DOI: 10.1177/1098612X241284766
https://doi.org/10.1177/1098612X241284766
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Petra Černá1,2 , Sneha Joseph Pugalendhi3,
Darren J Shaw3 and Danièlle A Gunn-Moore3

Abstract
Objectives The aim of the present study was to establish the incidence of dystocia in pedigree cat breeds and
investigate mortality rates in kittens up to the age of 12 weeks.
Methods A retrospective study was conducted that utilised convenience sampling. Registered cat breeders from
29 countries whose cats had given birth within a single year (2019) were asked to complete an online questionnaire.
This study is the third in a series over 30 years that have assessed changes in birth-related statistics in cat breeds.
Results Data were collected from 448 breeders on 853 litters, with 3560 live-born kittens from 45 pedigree breeds
(as per the queens’ breed). The incidence of dystocia that required veterinary intervention was 14.9% and varied
by breed (range 0–22.2%). Caesarean section was required for 10.7% of litters, most commonly in Cornish Rex
cats. Despite apparent breed variation, there was no statistically significant difference among breeds. Queens
aged over 5 years and litters of more than six kittens were associated with a reduced risk of dystocia, whereas a
longer gestation period increased the risk. Bengal cats had the highest cumulative kitten mortality up to the age of
12 weeks (23.4%). Significant breed differences (P <0.001) were noted, with Ragdoll and Norwegian Forest Cats
having lower litter mortality compared with Bengal and British Shorthair/Longhair cats.
Conclusions and relevance The incidence of dystocia in pedigree cats was higher than the historical values for non-
pedigree and pedigree cats. The age of the queen, gestation length and litter size affected the incidence of dystocia.
Kitten mortality was affected by the requirement for caesarean section, presence of birth defects and breed.

Keywords: Breeders; birth defects; pregnancy; kittens

Accepted: 14 August 2024

Introduction 69% of litters in a recent study) and fetal factors (which

Dystocia is a recognised cause of neonatal mortality and occurred in 31% of litters), or a combination of the two.3
stillbirth in pet cats (Felis catus), and pedigree cats have Obstructive dystocia typically occurs as a result of fetal
been reported as having a higher prevalence of dystocia malpresentation and malformations, and is associated
compared with their non-pedigree counterparts.1 with litter size (both small and large litters).1,4–6
Dystocia occurs as a result of either functional causes
(ie, uterine inertia) or obstructive causes (eg, maternal 1Department of Clinical Sciences, Colorado State University,
and fetal factors). Functional dystocia is seen when the Fort Collins, CO, USA
myometrium of the uterus fails to produce sufficient con- 2Small Animal Clinic, The University of Veterinary Sciences Brno,

tractions to expel the kittens through the birth canal. It Brno, Czech Republic
3The Royal (Dick) School of Veterinary Studies and The Roslin
can be either primary or secondary, with the most com-
Institute, University of Edinburgh, Edinburgh, UK
mon cause in cats being primary uterine inertia.2 Primary
uterine inertia occurs when the uterus fails to contract Corresponding author:
effectively from the start of labour, whereas secondary Danièlle A Gunn-Moore, BSc (Hon), BVM&S, PhD, MANZCVS
uterine inertia occurs when the uterus initially contracts (feline), FHEA, FRSB, FRCVS, RCVS Specialist in Feline Medicine,
The Royal (Dick) School of Veterinary Studies and The Roslin
effectively, but then weakens or stops contracting alto- Institute, University of Edinburgh, Easter Bush Veterinary Centre,
gether during the course of labour.2 Obstructive dystocia Edinburgh, Midlothian EH10 4BR, UK
may be attributed to maternal factors (which occurred in Email: Danielle.Gunn-Moore@ed.ac.uk

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2 Journal of Feline Medicine and Surgery 

Dystocia increases the risk of fetal death by hypoxia.1 Statistical analyses were performed using R (2023, The
Dystocia is managed through three primary methods: R Foundation for Statistical Computing). Generalised
medical intervention, such as administering oxytocin linear models with binomial errors (simple linear and
to strengthen uterine contractions and administering polynomial fits, as appropriate) were performed for
glucose or calcium where a deficit has been noted; non- the need for a c-section, occurrence of birth defects and
surgical manipulation, such as fetal manipulation; or litter mortality, with odds ratios (ORs) and associated
surgical intervention by performing a caesarean sec- 95% confidence intervals (CIs) calculated. Where no
tion (c-section).3,7 Dystocia has been reported to occur adequate fit was obtained, locally estimated scatterplot
in 0.4–8% of all cat litters, occurring more frequently in smoothing (LOESS) running averages are presented.
pedigree cats than non-pedigree cats.1,6 A 2017 Swedish Only breeds with at least 10 litters (n = 18 breeds) were
study reported the incidence of dystocia as 22 cats per analysed to reduce the impact of those with breeds with
10,000 cat-years at risk, with a nearly 10 times higher risk few litters. Pairwise post-hoc Tukey comparisons were
in purebred cats compared with domestic shorthair cats.8 undertaken to assess the differences between breeds.
Pet ownership has reached an all-time high in the UK.9 A P value <0.05 was considered statistically significant.
There were 11 million pet cats in the UK in 2022, with
pedigree cats increasing from 17% more than 5 years ago Results
to 45% in 2024.9 With the increasing demand for pedigree A total of 484 responses were received, with 27.9% of
cats in the UK, it remains vital to update our understand- breeders based in the UK. The rest came from outside
ing of how often dystocia occurs and what factors may the UK, of which 9.5% were from the USA. Most breed-
affect it. This study was the third in a series of studies ers were registered with Fédération Internationale Féline
that have run over 30 years.1,5 The aims of this study were (FIFe; 53.9%) and had considerable experience in breed-
to establish the current incidence of dystocia in differ- ing cats, with 37.8% having bred pedigree cats for more
ent pedigree cat breeds and investigate mortality rates in than 15 years (mean 15, range 1–48) (Figure 1a).
litters of different breeds in their first 12 weeks of life. Almost all of the breeders (n = 448, 99%) reported kitten
births in 2019, with 892 litters delivered. There was a max-
Materials and methods imum of 10 litters per breeder (Figure 1b). The 36 breeders
A questionnaire was designed and distributed online who did not have a litter born in 2019 were excluded from
through the survey platform JISC Surveys (available at further analysis. For the rest, 37.7% reported a single lit-
https://app.onlinesurveys.jisc.ac.uk). It was promoted ter (Figure 1b), with an overall mean of 2.34 litters. The
on the International Cat Care website and by social media number of litters per queen varied according to breeder
(eg, Facebook groups for cat breeders) and distributed experience, increasing up to 10 years’ experience, after
to known breeders. It was open from 10 April 2020 to which it plateaued (Figure 1c).
31 December 2021. Participants had to be aged at least Detailed information on litter composition was pro-
18 years and registered with a feline breeding organi- vided for 853 litters, with 3560 live-born kittens from
sation. All answers were anonymous. Ethical approval 45 pedigree breeds (as per the queens’ breed); 39 litters
was granted from the Royal (Dick) School of Veterinary were excluded because of incomplete information. In
Studies’ Human Ethical Review Committee. total, 18 breeds produced ⩾10 litters, resulting in 768 lit-
The questionnaire was based on the 2006 study by ters with 3215 kittens (Table 1). Ragdoll, Oriental group
Sparkes et al.5 It asked questions about the following: (1) and Cornish Rex cats had the longest gestation periods,
the breeding queens; (2) the birth of kittens; and (3) the whereas Korats, Sacred Birmans and Bengals had the
kittens’ first 12 weeks of life (Appendix 1). Participants shortest. Burmese cats had the largest litters, whereas
were asked how many litters had been born in 2019 (so Abyssinian/Somalis had the smallest, with the overall
that recent memory of a full year would be assessed) and mean litter size being 4.5 kittens.
answered the same questions for each litter.
Veterinary and breeder assistance
Statistical analysis More than one-third of litters (292/853, 34.2%) were
Responses were grouped by the breed of the queen reported as requiring veterinary or breeder assistance
for each litter, with variables of interest about the birth during delivery. Where veterinary help was needed,
recorded for each queen, plus the queen’s age, gestation this involved fetal manipulation and/or medication
length, litter size, kitten mortality percentage and number (eg, oxytocin), with or without c-section. Veterinary
of litters with birth defects. Sister breeds (Abyssinian and assistance was reported for 127 (14.9%) litters, with the
Somali; Exotic Shorthair and Persian; Balinese, Siamese, majority of these (91/127, 71.7%) needing a c-section (ie,
Oriental and Havana; Russian Blue and Nebelung) were 91/853 [10.7%] of all litters) (Table 1). Over 40% of c-sec-
combined for statistical analyses. The c-section rate was tions were a result of contractions ending (functional
used as a direct marker for dystocia. dystocia, 20.9%) and kitten(s) obstructing further labour
Černá et al 3

Figure 1 (a) Histogram showing the frequency of the number of years breeders had been breeding cats; (b) histogram
showing the frequency of the number of litters born in 2019; (c) scatterplot showing the number of litters born in 2019
against the number of years breeders had been breeding cats. The size of the points indicates the number of responses for
a particular combination. The thick line is a LOESS running average, with the shaded area representing the standard error.
LOESS = locally estimated scatterplot smoothing

(obstructive dystocia, 20.2%) (Figure 2); few (3.1%) were Several factors were found to affect the requirement
elective. for a c-section. Increased years of breeder experience
The highest percentage of c-sections (22.2%, 4/18) was were not associated with a decreased need for c-
seen in the Cornish Rex cats, followed by Burmese (20.8%, section (OR 0.98, 95% CI 0.96–1.00) (Figure 4a). However,
5/24) and Oriental group cats (20%, 14/70) (Figure 3). In older queens appeared to have a reduced risk (OR 0.81,
contrast, Korats and Neva Masquerades had no c-sec- 95% CI 0.68–0.96; P = 0.017) (Figure 4b); a c-section was
tions, while Exotic/Persians (1/44) and Ragdolls (1/39) needed in 12/186 (<6.5%) queens aged ⩾5 years (see
required c-sections in fewer than 3% of litters. Despite below), compared with 31/211 (15%) queens aged <3
apparent breed variation in the requirement for c-sec- years. Larger litters also appeared to have a reduced
tion, there were no statistically significant differences risk (OR 0.88, 95% CI 0.77–0.99; P = 0.042) (Figure 4c);
(P = 0.099). a c-section was needed in only 10/100 (10%) litters with
4 Journal of Feline Medicine and Surgery 

Table 1 Summary of pedigree breeds with at least 10 litters for each breed, including the number of litters, mean age of
the queens, mean gestation length, mean litter size, kitten mortality percentage, percentage of litters with obvious birth
defects and percentage of c-sections

Breed Litters (n) Mean age Mean gestation Mean litter Mean kitten Litters with C-section
of the length size mortality defects rate (%)
queen (days) (n) (%) (%)
(years)

Abyssinian/Somali 55 3.02 65.27 3.49 10.9 12.7 9.1

Balinese/ Siamese/ 70 2.99 66.15 4.83 17.8 11.4 20.0
Oriental/Havana
Bengal 19 3.32 63.95 4.95 23.4 5.3 10.5
BSH/BLH 160 3.61 65.16 4.88 18.1 13.1 13.1
Burmese 24 3.67 64.25 5.25 16.7 12.5 20.8
Cornish Rex 18 3.44 65.83 4.67 7.1 5.6 22.2
Devon Rex 31 3.13 64.26 3.90 12.4 22.6 9.7
Exotic/Persian 44 4.34 65.23 3.34 15.6 4.5 2.3
Korat 10 4.70 63.3 4.50 8.9 20.0 0
Maine Coon 95 3.75 65.38 5.17 13.0 12.6 10.5
Neva Masquerade 16 2.88 65.31 4.62 10.8 6.2 0
Norwegian Forest Cat 65 4.40 65.00 5.05 9.5 10.8 10.8
Ragdoll 39 3.38 66.22 4.87 7.4 2.6 2.6
Russian Blue/Nebelung 20 4.05 64.56 4.10 13.4 10.0 10.0
Sacred Birman 44 3.84 63.57 3.59 19.0 11.4 9.1
Selkirk Rex (Short/Long) 18 3.11 65.39 4.06 15.1 5.6 11.1
Siberian 26 3.65 64.19 4.50 7.7 7.7 11.5
Sphynx 14 4.43 64.93 4.57 21.9 21.4 14.3

Mean 42.67 3.65 64.89 4.46 13.81 10.89 10.19

Sister breeds were combined for the purposes of this study (ie, Abyssinian/Somali, Balinese/Siamese/Oriental/Havana and Russian Blue/
Nebelung). BSH and BLH were by far the most prevalent breeds, followed by Maine Coon cats
BLH = British Longhair; BSH = British Shorthair; c-section = caesarean section

complicated, non-linear relationship between increased

risk of c-section and gestation length. Risk decreased to a
minimum of 64 days before increasing again as gestation
increased to 70 days (Figure 4d).

Birth defects
Birth defects were reported in 10.9% of 853 litters. They
occurred most commonly in Devon Rex and Sphynx cats
(>20%) and least in Ragdoll and Exotic/Persian cats
(<5%) (Figure 5). Despite this, there were no significant
differences among breeds for the presence of birth defects
(P = 0.549). Descriptions of defects were given for 102 lit-
ters (Figure 6a); 32 (31.4%) kittens were reported to have
general malformations (eg, incomplete fetal develop-
ment, mummification), with the most common specific
Figure 2 Bar graph summarising the different reasons for malformations being cleft palate (n = 16, 15.7%), ompha-
cats requiring a c-section
locele (n = 15, 14.7%) and limb malformations (n = 15,
14.7%) (Figure 6b,c).
more than six kittens, compared with 19/103 (18%) litters The main factor associated with birth defects
with fewer than three kittens. This compares with 34/392 was increased litter size (OR 1.19, 95% CI 1.06–1.32;
(8.7%) litters of four or five kittens that required a c-sec- P = 0.002) (see Figure 1a in the supplementary mate-
tion (this is of interest as the mean litter size overall was rial), with birth defects increasing from less than 9%
4.5 kittens). In contrast to the linear declines associated in litters with fewer than five kittens to 14% in lit-
with older queens and larger litters, there was a more ters with more than six kittens. The relationship
Černá et al 5

Figure 3 Bar graph of the prevalence of c-section plotted against breed (for the 18 breeds with at least 10 litters born).
(n/nn) n = number of c-sections for breed, nn = total number of litters for a particular breed

Figure 4 Relationship between requirement for c-section and (a) number of years a breeder has been breeding; (b) age of
queen at birth of litter; (c) size of litter; and (d) gestation length. Size of points are scaled to the number of litters at a particular
x-value. Vertical lines are the 95% confidence intervals for each prevalence value. (a–c) Solid lines and associated shaded
areas represent the fitted linear binomial generalised linear model fit and standard errors. (d) Solid line and associated shaded
area represent a LOESS running average and standard error. LOESS = locally estimated scatterplot smoothing
6 Journal of Feline Medicine and Surgery 

Figure 5 Bar graph of the prevalence of birth defects per litter plotted against the 18 breeds that had at least 10 litters born in
2019. Values in parentheses indicate number of litters for the particular breed

Figure 6 (a) Bar graph summarising the frequency of different birth defects. (b,c) Birth defects in two kittens: (b) a midline
defect, omphalocele and limb deformity and (c) a cranial defect
Černá et al 7

Figure 7 (a) Bar graph of cumulative percentage mortality of kittens in the first 12 weeks of life (for the 18 breeds with at
least 10 litters born in 2019). (b) Stacked bar graph of proportional percentage mortality of kittens in the first 12 weeks of life
(for the18 breeds with at least 10 litters born in 2019). Vertical lines indicate 50% and 75% mortalities. Values in parentheses
indicate number of litters for the particular breed

between birth defects and gestation was non-linear, occurred at birth and in the first week (Figure 7a). Only
with a general decline to 6% at a gestation length of five breeds (Ragdoll, Norwegian Forest Cat, Maine Coon,
66 days, before rising to a second peak of 20% at a ges- BSH/BLH and Oriental group cats) had litters where
tation length of 69 days (see Figure 1b in the supple- additional mortality occurred between 8 and 12 weeks
mentary material). The age of the queen and the years of age. For 10/18 of the most common breeds, more than
of a breeder’s experience were not associated with birth 50% of mortalities were observed at birth (Figure 7b).
defects (P >0.066) (see Figure 1c,d in the supplementary Lower kitten mortality up to the age of 12 weeks was
material). associated with increased queen age (OR 0.90, 95% CI
0.84–0.96; P = 0.001) (see Figure 2a in the supplementary
Litter mortality material). The majority of kittens (96%) survived to 12
The highest mortality in kittens aged up to 12 weeks (still- weeks of age if they were born to queens aged over 8
births included) was for the Bengal breed (23.4%, 95% years compared with an 85% survival in kittens born to
CI 17.0–33.58), followed by the Sphynx (21.9%, 95% CI queens aged under 4 years. There was a more complicated
13.4–33.6) and Sacred Birman (19.0%, 95% CI 13.6–25.9) polynomial fit for litter survival with gestation length
(Figure 7). Cornish Rex cats had the lowest kitten mortal- (P <0.001) (see Figure 2b in the supplementary mate-
ity (7.1%, 95% CI 3.2–15.0), followed by Ragdolls (7.4%, rial). Survival increased rapidly from short (<57 days)
95% CI 4.4–12.1). There were statistically significant dif- gestation lengths, plateauing to over 80% if the gestation
ferences in litter mortality among the breeds (P <0.001), length was more than 61 days, with an apparently higher
with Ragdoll and Norwegian Forest Cats having lower plateau of over 93% if the gestation length extended to
rates than Bengal and British Shorthair and Longhair more than 69 days (though this only represented 19 lit-
(BSH/BLH) cats. ters). Greater mortality by the age of 12 weeks was associ-
The age at death varied among the breeds. For three ated with c-section (OR 3.43, 95% CI 2.70–4.34; P <0.001).
breeds (Korat, Neva Masquerade and Russian Blue) The survival rate of kittens living to 12 weeks in queens
(Figure 7a,b), kitten deaths occurred only at birth and who needed a c-section was lower (69%) than the sur-
in the first week of life. With the exception of Ragdolls vival rate of kittens living to 12 weeks in queens who
(43.2%), more than 70% of kitten deaths in all breeds did not require a c-section (88%). A similar pattern was
8 Journal of Feline Medicine and Surgery 

observed for birth defects (OR 2.79, 95% CI 2.22–3.49; Litter size was also found to affect the incidence of dys-
P <0.001), with the survival rate of kittens living to tocia, with litters of one or two kittens having an increased
12 weeks in litters with birth defects (73%) being lower incidence of dystocia compared with litters with a mean
than in litters without birth defects (88%). Increasing litter size of 4.5 (15% vs 8.7%, respectively). Though litter sizes
size was associated with a polynomial change in mortal- of more than six kittens appeared to have a decreased inci-
ity (P = 0.003) (see Figure 2c in the supplementary mate- dence of dystocia, care needs to be taken in interpreting
rial), with an increasing percentage of kittens surviving this, given smaller sample sizes. In contrast, a previous
to 12 weeks in queens as litter size increased, peaking at study found increased litter sizes (more than six kittens)
91% for a litter of five kittens, before declining to less than had an increased risk of dystocia (eg, 34% of litters with
75% as litter size increased further. In contrast, increasing nine kittens experienced dystocia vs 5% of litters with six
breeder experience was not associated with decreased kittens).6 That study also found that litters of five or six
litter mortality (OR 1.00, 95% CI 0.99–1.02; P = 0.242) (see kittens had the least dystocia (approximately 5%), with
Figure 2d in the supplementary material). single-kitten litters also having an increased risk (12.5%),6
similar to the findings of the current study. Very small
Discussion and very large litters can result in dystocia due to under-
This study is the third in a series of three question- or overdistension of the uterus, respectively; in addition,
naire-based surveys that have been conducted over overly large kittens are most likely to occur in small lit-
30 years to assess the prevalence of dystocia, requirement ters and these kittens are at risk of dystocia from fetal–
for c-sections and mortality in kittens up to the age of maternal size mismatch.1,6,8 Although previous stud-
12 weeks across different pedigree cat breeds. In the cur- ies found that mean kitten size relates to the number of
rent study, 10.2% of litters required a c-section. This has kittens in the litter,6,8 this was not investigated in the
increased compared with 5.8% for non-pedigree cats and current study as kitten birth weights were not collected.
7–10% for pedigree cats in 1995,1 and 8.0% for pedigree Further studies are needed to investigate the association
cats in 2006.5 The prevalence of dystocia varied among between kitten size, litter size and the effect on dystocia
breeds, though not significantly. This could have resulted to clarify this relationship.
from small numbers of litters in certain breeds. Of the 18 The Exotic/Persian cats had one of the lowest rates
breeds with at least 10 litters, only the BSH/BLH cats had of dystocia in the current study (2.3%), consistent with
more than 100 litters (Table 1). Perhaps unexpectedly, other another study that found a low IRR for dystocia for these
studies have also found breed not to affect dystocia rates.5,6 breeds.8 However, the decrease in dystocia (from 7.5%)1
This may be because other, non-breed related factors, such occurred while the brachycephalic features, such as the
as litter size, queen age and gestation length, have a bigger reduction of facial bones and deformation of the neu-
impact on dystocia rates.5 Obesity has also been shown to rocranium, have become more pronounced.10 This was
influence rates of dystocia, and has been linked with the unexpected, as the increasing severity of brachycephalic
rate of stillbirths;8,10 however, the body condition score of features would be expected to predict more dystocia
queens was not tracked in the current study. In contrast, owing to the decrease in the wedge effect of the kitten’s
another study found breed to be a significant risk factor nose, which is believed to be necessary to engage the
for c-section, having found differences in incidence rate maternal pelvis to stimulate labour.1,10 The current study
ratios (IRRs) among breeds, with BSH/BLH and Oriental also found the cumulative kitten mortality of Exotic/
cats having increased IRRs compared with other breeds.8 Persian cats to be markedly lower than in a previous
Different breeds may have different risks of dystocia study (15.6% vs 25%).5
owing to their head and/or body shape, or as a result of One possible reason behind the reduced dystocia and
non-phenotypic genetic changes.2,8 For example, brachy- kitten mortality in Exotic/Persian cats could be the near
cephalic queens may have a higher risk of dystocia and/ elimination of autosomal dominant polycystic kidney
or c-sections owing to changes in pelvic conformation.11 disease (PKD) in the breed.12 Targeted intervention (eg,
This study found that queens aged over 5 years had a by the Governing Council of the Cat Fancy and FIFe)
decreased risk of requiring a c-section. It is possible that mandating that breeding queens be genetically tested
older queens who had previously given birth to healthy for the PKD gene defect (PKD1) has decreased the preva-
kittens with no complications were bred from prefer- lence of PKD in Exotic/Persian cats from 28% in 2005 to
entially. This supports an older study that suggested it 2% in 2016.12 Newer studies have suggested that PKD
is possible to breed for a low level of dystocia by selec- in cats may have genetic heterogeneity, as seen in peo-
tively breeding from queens who previously bred easily.1 ple, and have implicated the PKD2, DZIP1L and PKDH1
In contrast, younger queens who experienced dystocia genes.13,14 Moreover, the genes responsible for PKD in
or birth defects were likely to be retired from breed- humans have also been demonstrated to show pleiot-
ing. Another study found a decreased risk of c-section ropy, influencing multiple biological processes, such
with increasing parity, which roughly corresponds with as the vascular and skeletal system, beyond just caus-
increasing queen age.5 ing PKD.15 It may be that the targeted intervention in
Černá et al 9

reducing PKD in the breed may have indirectly selected to increased kitten mortality.3 Another study reported
for a fitter breeding population, leading to a decrease lower vitality scores in kittens delivered by emergency c-
in the rates of dystocia and cumulative kitten mortality section compared with those delivered naturally. 16
given the likely pleiotropic nature of the genes involved. Postoperative pain and stress associated with a c-
It is still unclear what role, if any, reducing the preva- section may result in the queen being reluctant to suckle
lence of PKD has played in reducing the incidence of her kittens; it may also reduce colostrum flow, prevent-
dystocia and/or overall kitten mortality in this breed. ing the kittens from suckling immediately and leading
More research is needed to determine how pleiotropic to failure in passive transfer of immunity to the kittens.
PKD-relevant genes are in Exotic/Persian cats and what Colostrum-deprived kittens are shown to have lower
effects they may have on overall reproductive fitness. levels of immunoglobulins even when supplemented
Birth defects were found in 10.9% of litters, which was with milk replacers or fostered onto surrogate mothers.18
lower than in 2006 (14.3%).5 Litter size was linked to birth This can lead to a greater risk of infection during this
defects in both studies, with larger litters being associated period, which, in turn, can result in higher kitten mortal-
with more birth defects and stillbirths.5,6 Increased num- ity. In the current study, most neonatal deaths occurred in
bers of birth defects in large litters could result from poorer the first week of life, as has been reported previously.5,8
kitten development in utero due to less space within the Most deaths in week 1 of life are unlikely to result from
uterus and/or nutritional deficiencies.16 Although breed infectious disease as colostrum should protect kittens in
was found not to be a significant factor for birth defects the first 4 weeks of life; however, the duration of mater-
in the current study, a previous study has postulated nally derived immunity can be variable.19 Kitten deaths
that congenital defects are heritable and breed related, in the first week of life are more often related to dystocia-
though further research is needed to look into this.6 It has related hypoxia and trauma.20 Although a previous study
been reported that litter sizes vary among breeds,5 and reported that non-pedigree kittens were more likely to
if certain breeds are more prone to having larger litters, have a diagnosis of feline panleukopenia than pedigree
they may (potentially) be at a higher risk of more birth kittens,6 factors that may impact kitten mortality as a
defects due to the increased litter size. More research is result of infectious diseases were not within the scope
needed to understand the complex nature of the different of this study; a larger study population would need to
variables involved and whether there are confounding or include a non-pedigree population for comparison.
correlative effects. The present study has some limitations. The main
The current study found that kitten mortality up to limitations were the convenience sampling method uti-
12 weeks of age was affected by the queen’s breed and lised (vs a true randomised prevalence study) and the
age, gestation length, delivery by c-section and the pres- retrospective nature of the study. Another limitation was
ence of birth defects. Ragdolls and Norwegian Forest Cats that although over 800 queens were included, the num-
had statistically lower kitten mortality compared with ber of queens within each breed was sometimes limited.
Bengal and BSH/BLH cats; however, why this should be Respondents were only asked the kittens’ breed; this made
the case is currently unclear. Breed variations have been it difficult to ascertain the queen’s breed when breeders
previously demonstrated to be a factor in kitten mortality, had several litters from queens of different breeds. The
with Oriental Shorthair/Siamese and Exotic/Persian cats queen’s breed had to be inferred from the kitten’s breed
having a much higher rate than other pedigree breeds and survey responses were excluded where this was not
(>10%).6 Kitten mortality was reduced in queens aged possible. In addition, not all breeds were equally repre-
under 8 years, as has previously been suggested, whereas sented, which may have led to values for some breeds
older queens may be prone to higher rates of kitten being unrepresentative of the true population; however,
mortality and stillborn kitten rates.6 A gestation length the same can be said of other similar studies.1,5
of more than 61 days was also shown to decrease kit-
ten mortality. Gestations of ‘species appropriate length’ Conclusions
usually result in the kittens being born fully developed This study is the third to be conducted over a period of
and strong enough to suckle efficiently; unsurprisingly, more than 30 years that details the changing face of feline
kittens born at the extremes of the range have a lower dystocia and kitten mortality. It shows that dystocia is
chance of being viable.5 Although it is possible that some more common in pedigree cats than seen historically;
specific cat breeds have gestation lengths slightly longer however, significant improvements have occurred in cer-
or shorter than most cats, this has not yet been reported. tain breeds, specifically the Persian/Exotic breed. The
Birth defects and c-sections were associated with high rates of dystocia varied among breeds, although breed
kitten mortality up to 12 weeks of age. A recent study was not a significant factor affecting this. Instead, non-
where queens were presented to a veterinary hospi- breed factors, such as age, litter size and gestation length,
tal for dystocia reported that overall neonatal survival have a significant impact on the rates of dystocia. Litter
to discharge was as low as 66%, and that dystocia led mortality up to 12 weeks of age was affected by breed, age
10 Journal of Feline Medicine and Surgery 

of the queen, gestation length, delivery by c-section and neonatal outcomes in 35 cases (2009–2020). J Feline Med
the presence of birth defects. Surg 2022; 24: 344–350.
4 Robbins MA and Mullen HS. En bloc ovariohysterectomy
as a treatment for dystocia in dogs and cats. Vet Surg 1994;
Acknowledgements The authors are very thankful to all
23: 48–52.
breeders for answering the questionnaire. The authors are also
5 Sparkes AH, Rogers K, Henley WE, et al. A questionnaire-
thankful to Dr Andrew Sparkes for sharing the original ques-
based study of gestation, parturition and neonatal mortal-
tionnaire, and to International Cat Care and the International
ity in pedigree breeding cats in the UK. J Feline Med Surg
Society of Feline Medicine for their support.
2006; 8: 145–157.
6 Holst BS and Frössling J. The Swedish breeding cat: popu-
Supplementary material The following files are available
lation description, infectious diseases and reproductive
as supplementary material:
performance evaluated by a questionnaire. J Feline Med
Supplementary Figure 1: Relationship between prevalence of
Surg 2009; 11: 793–802.
birth defects and (a) size of litter, (b) gestation length, (c) age
7 Holst BS. Feline breeding and pregnancy management:
of queen at birth of litter and (d) number of years a breeder has
what is normal and when to intervene. J Feline Med Surg
been breeding.
2022; 24: 221–231.
Supplementary Figure 2: Relationship between percentage of
8 Holst BS, Axnér E, Öhlund M, et al. Dystocia in the cat
kittens alive at 12 weeks and (a) age of queen at birth of litter,
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Conflict of interest The authors declared no potential 10 Schmidt MJ, Kampschulte M, Enderlein S, et al. The rela-
conflicts of interest with respect to the research, authorship, tionship between brachycephalic head features in modern
and/or publication of this article. Persian cats and dysmorphologies of the skull and internal
hydrocephalus. J Vet Intern Med 2017; 31: 1487–1501.
Funding The authors received no financial support for the 11 Monteiro CL, Campos AI and Madeira VL. Pelvic differ-
research, authorship, and/or publication of this article. ences between brachycephalic and mesaticephalic cats
and indirect pelvimetry assessment. Vet Rec 2013; 172: 16.
Ethical approval The work described in this manuscript DOI: 10.1136/vr.100859.
involved the use of non-experimental (owned or unowned) 12 O’Neill DG, Romans C, Brodbelt DC, et al. Persian cats
animals. Established internationally recognised high standards under first opinion veterinary care in the UK: demogra-
(‘best practice’) of veterinary clinical care for the individual phy, mortality and disorders. Sci Rep 2019; 9. DOI: 10.1038/
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use of cadavers. Ethical approval from a committee was there- 13 Schirrer L, Marín-García PJ and Llobat L. Feline polycystic
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Informed consent Informed consent (verbal or written)
Outcomes (KDIGO) Controversies Conference. Kidney Int
was obtained from the owner or legal custodian of all animal(s)
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16 Bilkei G. Effect of the nutrition status on parturition in
or people are identifiable within this publication, and therefore
the cat [article in German]. Berl Munch Tierarztl Wochenschr
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