TERATOGENS
any factor chemical or physical that adversely affects the fertilized ovum, embryo, or
fetus.
A fetus needs sound genes and healthy intrauterine environment that protects it from the
influence of teratogens.
EFFECTS OF TERATOGENS ON THE FETUS
FACTORS
1. Strength of the teratogen
In small amount- causes no damage
Large doses- causes serious fetal defects or death
2. Timing of the teratogenic insult
If teratogen is introduced during implantation, either the zygote is destroyed or
appears unaffected
If the insult occurs when the main body systems are being formed ( in the 2nd to 8th
weeks of embryonic life) the fetus is very vulnerable to injury.
During the last trimester = potential harm decreases because all the organs of the
fetus has been formed.
Deformities usually occur in the early embryonic life are the effects caused by the
organisms of syphilis and toxoplasmosis.
3. Teratogen’s affinity for a specific tissue
Lead attacks and disables nervous tissue
Thalidomide causes limb defects
Tetracycline causes tooth enamel deficiency and long bone deformities
Rubella virus can affect organs like the eyes, ears, heart, and brain
TERATOGENIC MATERNAL INFECTIONS
Involve either sexually transmitted or systemic infections.
The group of diseases is under the umbrella TORCH
All these infections are known to cross the placenta affects the fetus during pregnancy
tORCH screen was developed as an immunologic survey to determine infections from
the pregnant woman and the newborn
infections that cross the placenta can be viral, bacterial, or protozoan
cause milk, flulike symptoms in a woman but has a serious effect to the fetus.
COMMON TERATOGENIC INFECTIONS:
1. T- TOXOPLASMOSIS
A protozoan infection spread most commonly through contact with uncooked
meat, handling cat stool
The woman experiences no symptoms of the disease except a few days of
malaise a and posterior cervical lymphadenopathy
If the infection crosses the placenta= it causes central nervous system damage,
hydrocephalus, microcephaly, intracerebral calcification and retinal deformities’
Pyrimethamine , an antiprotozoal agent may be used.
= an antifolic acid drug so it is not administered early in pregnancy to prevent
folic acid levels.
Management:
Prepregnancy serum analysis to identify women who have never had a
disease and are susceptible ( about 50% of women)
Avoid eating undercokedmeat
Avoid working in a soil in which cats had made use for defecation.
2. O - OTHER VIRAL DISEASES
a. Syphillis
A sexually transmitted infection
Can place the fetus at risk for congenital syphilis
Causative agent: Treponema Pallidum- can extremely damaged the fetus after
the 16th-18th week of intrauterine life, when the cytotrophoblastic layer of the
placental villi has atrophied and no longer protects it.
If treated earlier, the fetus is rarely affected.
If left untreated beyond the 18th week , deafness, cognitive challenge,
osteochondrosis and fetal death are possible.
Newborn with congenital syphilis may have congenital anomalies, extreme
rhinitis and a syphilitic rash, indicating high-risk at birth.
Management”
Safer sex practice
Early detection
Immediate treatment with antibiotic
Serologic screening should be done in the 1st prenatal visit
b. Lyme disease
A multisystem disease caused by Spirochete Borrelia Burgdorferi
Spread by a spread of a deer tick.
After a tick bite, typical skin rash (erythema chronicum migrans)develops,
pain in large body joints
Infect in pregnancy can result in spontaneous miscarriage or severe
congenital anomalies.
Management:
Women anticipating becoming pregnant or who are pregnant should
avoid areas such as wooded or tall greasy areas
If hiking in these areas, woman should avoid the use of tick repellants
containing diethyltoluamide because the ingredient is teratogenic.
Wear long light colored slacks tucked into her socks to prevent leg s from
being esposed.
After returning from hiking, woman should inspect her body carefully and
immediately remove the ticks
Treatment for nonpregnant: tetracycline and doxycycline but cannot be
used during pregnancy because they can cause tooth discoloration and
possibly long bone malformation
Penicillin can be used by the pregnant woman to reduce symptoms.
c. Infections that cause illness at birth
A number of infections are not teratogenic to the fetus during pregnancy but
are harmful if they are present at the time of birth like gonorrhea, candidiasis,
Chlamydia, streptococcus B and hepatitis B.
3. R- RUBELLA
Fetal damage from maternal infection with rubella includes:
Deafness
mental and motor challenges
Cataracts
cardiac defects ( patent ductus arteriosus and pulmonary stenosis)
retarded intrauterine growth
thrombocytopenic purpura
dental and facial clefts- cleft lip and palate
a woman who is not immunized before pregnancy cannot ne immunized
during pregnancy because the vaccine uses a live virus that would have
effect s similar to those occurring with a subclinical case of rubella.
After rubella immunization, not advised to become pregnant for 3 months until
the rubella virus is no longer active.
Should not be in contact with children who have rubella.
4. C - CYTOMEGALOVIRUS
A member of the herpes virus family
Transmitted through droplets infection from person to person
40%-100% of women are estimated to have been infected with CMV before
pregnancy.
Crosses the placenta causing congenital CMV infection
Effects:
Hydrocephalus
Microcephaly
Spasticity
Eye damage
Deafness
Chronic liver diasease
Blueberry -muffin lesions
Management:
Thorough handwashing before eating
Avoid crowds of young children
5. H - HERPES SIMPLEX VIRUS (GENITAL HERPES INFECTION)
The virus spreads into the bloodstream and crosses the placenta to the fetus.
1st trimester – causes severe congenital anomalies or spontaneous miscarriage
2nd or 3rd trimester – high incidence of premature birth, intrauterine growth
retardation and continuing infection of the newborn at birth.
Management:
Acyclovir (Zovirax)
Safe sex
Potential Teratogenicity of Vaccines
Live virus vaccines such as measles, mumps, rubella and poliomyelitis are
contraindicated during pregnancy because they may transmit the viral infection to the
fetus.
TERATOGENICITY OF DRUGS
NOT all drugs crosses the placenta like heparin since it has a large molecular size.
Herbs, ginseng are not safe during pregnancy
Any drug or herbal supplement under certain circumstances may be detrimental to fetal
welfare. Therefore during pregnancy, women should not take any drug or supplement
not approved by the physician.
“Pregnancy applies ONLY to PRESCRIPTION DRUGS
Thalidomide – classic teratogenic drug
Causes:
Amelia or pocomelia when taken between 34th and 45th day of pregnancy.
Narcotics such as meperidine (demerol) and heroin causes intrauterine growth
retardation.
TERATOGENICITY OF ALCOHOL
High incidence of alcohol causes congenital deformities an cognitive impairment.
Fetal alcohol syndrome - SGA
TERATOGENICITY OF CIGARETTES
Causes growth retardation.
Greater risk for sudden infant death syndrome
LBW
ENVIRONMENTAL TERATOGENS
a.Metal and Chemical Hazard
Pesticides and carbon monoxide
Arsenic (byproduct of copper and lead smelting, used in pesticides, paints and leather
processing
Formaldehyde – used in paper manufacturing
Mercury – used in manufacture of electrical apparatuses
Lead ingestion – may lead to newborn neurologically and cognitively challenge
b.Radiation
Produces a range of malformations
Can damage nervous system, brain and retinal innervation
Before implantation : fetal death
Critical period : from implantation to 6 weeks of pregnancy
RULE : “ All women of childbearing age should be exposed to pelvic x-rays on the 1st 10
days of menstrual cycle.”
Pregnancy test prior the X-rays
Sonogram and MRI may replaced x-ray examinations
Increase the risk of cancer among children
X-ray with lead apron to shield her pelvis during the procedure
Fluoroscopy uses lower radiation doses
Long term use of slight radiation sources (word processor, computer or cellular phone) are
still on investigation
c.Hyperthermia
Detrimental to fetal growth w/c interferes with cell metabolism
Acquired through saunas, hot tubs, welding or steel making
Maternal fever early in pregnancy can cause abnormal fetal brain development
and possible seizure disorder, hypotonia and skeletal deformities
d.Teratogenic Maternal Stress
Emotionally disturbed pregnancy could produced physiologic changes through
its effect on the sympathetic division of the autonomic nervous system
Can cause constriction of the peripheral blood vessels (fight-or-flight
syndrome)
If anxiety is prolonged – uterine vessels constrict – interfere with blood and
nutrient supply to a fetus
* passive immunization from measles lasts over a year
