Effects of teratogens
The most common effects of teratogens on the fetus are:
- Spontaneous abortion
- Defects in development
- Malformations (major or minor)
- Intrauterine growth retardation
- Mental retardation
- Mutagenesis (causing genetic mutation)
Some drugs, such as warfarin, phenytoin, and alcohol, cause a group of effects specific for exposure to that agent. These recognizable patterns of congenital anomalies are named after the drug known to cause them, thus the terms “fetal alcohol syndrome,” “fetal warfarin syndrome” or “fetal hydantoin syndrome.”
Fetal alcohol syndrome is defined as the presence of several of the following: prenatal and postnatal growth retardation, mental retardation, poor coordination, hypotonia, hyperactivity, microcephaly, short upturned nose, micrognathia or retrognathia in infancy, short palpebral fissures, hypoplastic philtrum, thinned upper lips, and, less frequently, anomalies of the eyes, mouth, heart, kidneys, gonads, skin, muscle, and joints. This group of defects is seen in mothers with high-dose alcohol intake during their pregnancies.
Fetal warfarin syndrome is seen in up to 25% of fetuses with first-trimester exposure to coumarins. This distinct pattern of anomalies includes nasal hypoplasia, depressed bridge of nose, and bone stippling on x-ray. A distinctly different pattern is seen with second- and third-trimester exposure to coumarins, featuring optic atrophy, cataracts, mental retardation, microcephaly, microphthalmia, deafness, growth retardation, scoliosis, seizures and hemorrhage.