2. A teratogen is an agent that can disturb the
development of the embryo or fetus. Teratogens
halt the pregnancy or produce a congenital
malformation (a birth defect). Classes of
teratogens include radiation, maternal infections,
chemicals, and drugs
3. Birth defects are known to occur in 3-5% of all newborns.
They are the leading cause of infant mortality in the United
States, accounting for more than 20% of all infant deaths.
They can do direct damage to the fetus, causing abnormal
development.
They can compromise the function of the placenta, often by
constricting blood vessels and reducing the supply of
oxygen and nutrients from the mother to the fetus. This can
lead to underdevelopment or low birth weight, which are
risk factors for birth defects.
They can trigger forceful uterine contractions, potentially
injuring the fetus or prompting premature birth.
4.
5. Category A Adequate and well-controlled studies have failed to demonstrate a risk to
the fetus in the first trimester of pregnancy (and there is no evidence of
risk in later trimesters).
Category B Animal reproduction studies have failed to demonstrate a risk to the fetus
and there are no adequate and well-controlled studies in pregnant women.
Category C Animal reproduction studies have shown an adverse effect on the fetus
and there are no adequate and well-controlled studies in humans, but
potential benefits may warrant use of the drug in pregnant women despite
potential risks.
Category D There is positive evidence of human fetal risk based on adverse reaction
data from investigational or marketing experience or studies in humans,
but potential benefits may warrant use of the drug in pregnant women
despite potential risks.
Category X Studies in animals or humans have demonstrated fetal abnormalities
and/or there is positive evidence of human fetal risk based on adverse
reaction data from investigational or marketing experience, and the risks
involved in use of the drug in pregnant women clearly outweigh potential
benefits.
Category N FDA has not classified the drug.
6.
7.
8. The best course is to prevent teratogen exposure,
or reduce the exposure as much as possible.
Prevention is complicated because very often
women may not realize they are pregnant until the
middle of the period of susceptibility.
Retinoic acid, for example, has a period of
susceptibility from days 20-35 after conception—a
time when many women might not realize they are
pregnant.
9. Warfarin Pregnancy category - X
Trimesters of risk - First, second, and third
Associated defects and complications - Deformities of the axial and appendicular skeleton;
also, a hypoplastic nose, eye abnormalities, mental retardation, brachydactyly, and
scoliosis
Penicillamine Pregnancy category - D
Trimester of risk - Unknown
Associated defects and complications - Variable; possible connective-tissue defects,
cerebral palsy, hydrocephalus, skeletal defects, cleft palates, and fetal toxicity
(resorptions)
Phenobarbital or methylphenobarbital Pregnancy category - D
Trimester of risk – third trimester
Associated defects and complications - Phenobarbital or methylphenobarbital slightly
increases the risk of cleft palate or lip and congenital heart disease. These drugs can
cause fetal addiction and newborn withdrawal symptoms or newborn hemorrhage
Fluconazole Pregnancy category - C (single dose); D (multiple doses)
Trimester of risk - First
Associated defects and complications - Craniofacial, skeletal, and cardiac effects
10. ACE inhibitors . category C,D
Trimesters of risk - First ,second and third trimesters
ligohydramnios, intrauterine growth restriction (IUGR), premature labor, and fetal and
neonatal renal failure. Reported birth defects included bony malformations, limb
contractures, persistent patent ductus arteriosus, pulmonary hypoplasia, respiratory
distress syndrome, prolonged hypotension, neonatal death, fetal calvarial hypoplasia or
aplasia, oligohydramnios, and renal anomalies.
Angiotensin II receptor antagonists Pregnancy category - D
Trimesters of risk - First, second, and third
Associated defects and complications - Hypotension, renal dysplasia, anuria or oliguria,
oligohydramnios, IUGR, pulmonary hypoplasia, patent ductus arteriosus, incomplete
ossification of the skull, and intrauterine or neonatal death
Aspirin Pregnancy category - D
Trimesters of risk - First, second, and third
Associated defects and complications - Unclear; may be associated with an increased risk
of gastroschisis
Tetracyclines Pregnancy category - D
Trimesters of risk - Second and third (20th gestational week or later)
Associated defects and complications - Dental staining
11. Aminoglycosides Pregnancy category D
Trimester of risk - Not consistent
Some neonates have had hearing defects, whereas others have had vestibular
problems. Some offspring had inner ear damage, whereas others did not.
Benzodiazepines Pregnancy category - D or X
Trimesters of risk: The first, second, and third
Associated defects and complications - Unclear; potential for isolated oral cleft
Carbamazepine Pregnancy category – D
Trimesters of risk - First, second, and third
Associated defects and complications - Unique facial appearance and
underdevelopment of the fingers, toes, and nails; developmental delay
Corticosteroids Pregnancy category - C
Trimester of risk - First
Associated defects and complications - Reduced birth weight, increased risk of
preeclampsia, and increased risk of oral and lip clefts
