Influences on Prenatal Development
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Teratogens are extrauterine agents that cause structural abnormalities in the embryo or fetus.
Types of teratogens include chemicals (alcohol), maternal diseases and illnesses (rubella and diabetes), and environmental hazards (radiation).
Fetal alcohol syndrome is a type of retardation that can result from use of alcohol during pregnancy.
TERMS
Fetal alcohol syndrome
Teratogens
Whatever affects the mother can affect the fetus. Teratogens (from teras, meaning “monster,” and genesis, meaning “origin”) are extrauterine agents that cause structural abnormalities in the developing child. They include chemical substances, infectious diseases, and environmental hazards to which the mother is exposed during pregnancy. Some chronic health conditions, such as diabetes, are not extrauterine agents, but can nevertheless affect the fetus.
Teratogens are extrauterine agents that cause structural abnormalities in the developing child.The relationship between the timing of prenatal exposure to a teratogen and fetal development is critical. Exposure from the 3rd to 8th week—when 95% of the major organ systems form—can result in major abnormalities of vital structures, such as arms, legs, heart, and eyes. Later exposure may cause organs to malfunction. Long-term exposure (e.g., to alcohol) is most devastating of all. The effects are usually both irreversible and preventable.
CHEMICAL SUBSTANCESAlcohol interferes with fetal cell division and growth throughout pregnancy. During the third trimester in particular, alcohol adversely alters development of the central nervous system (CNS) and brain. Fetal alcohol syndrome is characterized by retarded growth before and after birth; unusual facial features, such as a small head, flat philtrum (no depression between the nose and upper lip), and small widely spaced eyes; and structural abnormalities of the palate, heart, kidneys, and bladder. The most striking deficit is impaired intellectual capacity, especially mental retardation, which is often accompanied by seizures. Withdrawal from alcohol causes tremors, increased muscle tone, and irritability. Fetal alcohol syndrome is found in approximately 40% of infants born to alcoholics. There is no known minimum amount of alcohol that can be safely consumed during pregnancy. Women are best advised to abstain from alcohol if they are trying to become pregnant, and during pregnancy.
Fetal alcohol syndrome is found in approximately 40% of infants born to alcoholics.Cocaine increases maternal and fetal heart rates and blood pressures, decreases blood flow to the fetus, and causes uterine contractions. Complications of cocaine use during pregnancy may include fetal death, spontaneous abortion, premature birth, infants small for gestational age (SGA), and ventricular hemorrhage (bleeding into the brain). Infants also experience abnormalities of the genitourinary system and neurological irritability, such as disturbed wake-sleep cycles, increased muscle tone, difficulty being soothed, and learning disabilities.
Smoking decreases blood flow to the placenta, constricts blood vessels in the uterus, and interferes with maternal absorption of vitamins and calcium. Mothers who smoke—especially older mothers—have a higher incidence of premature birth and placenta previa (separation of the placenta from the uterine wall). Their full-term infants are also more likely to have lower birth weights.
There is no known minimum amount of alcohol that can be safely consumed during pregnancy. Women are best advised to abstain from alcohol if they are trying to become pregnant, and during pregnancy.Medications that pregnant women use, both prescribed and over-the-counter, are also chemical substances (Figure 18-1). Women should consult with their health care provider regarding any medications they may take during pregnancy.
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