Good prenatal care is essential. The developing child is most at risk for some of the most severe problems during the first three months of development. Unfortunately, this is a time at which many mothers are unaware that they are pregnant. Today, we know many of the factors that can jeopardize the health of the developing child. The study of factors that contribute to birth defects is called teratology. Teratogens are environmental factors that can contribute to birth defects, and include some maternal diseases, pollutants, drugs and alcohol.
Factors influencing prenatal risks: There are several considerations in determining the type and amount of damage that might result from exposure to a particular teratogen [Berger, 2005]. These include:
- The timing of the exposure: Structures in the body are vulnerable to the most severe damage when they are forming. If a substance is introduced during a particular structure’s critical period [time of development], the damage to that structure may be greater. For example, the ears and arms reach their critical periods at about 6 weeks after conception. If a mother exposes the embryo to certain substances during this period, the arms and ears may be malformed.
- The amount of exposure: Some substances are not harmful unless the amounts reach a certain level. The critical level depends in part on the size and metabolism of the mother.
- The number of teratogens: Fetuses exposed to multiple teratogens typically have more problems than those exposed to only one.
- Genetics: Genetic make-up also plays a role on the impact a particular teratogen might have on the child. This is suggested by fraternal twins exposed to the same prenatal environment, but they do not experience the same teratogenic effects. The genetic make- up of the mother can also have an effect; some mothers may be more resistant to teratogenic effects than others.
- Being male or female: Males are more likely to experience damage due to teratogens than are females. It is believed that the Y chromosome, which contains fewer genes than the X, may have an impact.
Figure 2.9 illustrates the timing of teratogen exposure and the types of structural defects that can occur during the prenatal period.
Figure 2.9 Critical Periods of Prenatal Development
Alcohol: One of the most commonly used teratogens is alcohol, and because half of all pregnancies in the United States are unplanned, it is recommended that women of child-bearing age take great caution against drinking alcohol when not using birth control or when pregnant [CDC, 2005]. Alcohol use during pregnancy is the leading preventable cause of intellectual disabilities in children in the United States [Maier & West, 2001]. Alcohol consumption, particularly during the second month of prenatal development but at any point during pregnancy, may lead to neurocognitive and behavioral difficulties that can last a lifetime. Binge drinking [5 or more drinks on a single occasion] or 7 or more drinks during a single week place a child at risk.
In extreme cases, alcohol consumption during pregnancy can lead to fetal death, but also can result in Fetal Alcohol Spectrum Disorders [FASD], which is an umbrella term for the range of effects that can occur due to alcohol consumption during pregnancy [March of Dimes, 2016a]. The most severe form of FASD is Fetal Alcohol Syndrome [FAS]. Children with FAS share certain physical features such as flattened noses, small eye holes, and small heads [see Figure 2.10]. Cognitively, these children have poor judgment, poor impulse control, higher rates of ADHD, learning issues, and lower IQ scores. These developmental problems and delays persist into adulthood [Streissguth, Barr, Kogan, & Bookstein, 1996] and can include criminal behavior, psychiatric problems, and unemployment [CDC, 2016a]. Based on animal studies, it has been hypothesized that a mother’s alcohol consumption during pregnancy may predispose her child to like alcohol [Youngentob, Molina, Spear, & Youngentob, 2007].
Facial FeaturePotential Effect of Fetal AlcoholHead sizeBelow-average head circumferenceEyesSmaller than average eye opening, skin folds at corners of eyesNoseLow nasal bridge, short noseMidfaceSmaller than average midface sizeLip and philtrum Thin upper lip, indistinct philtrum
Figure 2.10 Fetal Alcohol Spectrum Disorders
Tobacco: Another widely used teratogen is tobacco. According to Tong et al. [2013] in conjunction with the Centers for Disease Control and Prevention, data from 27 sites in 2010 representing 52% of live births, showed that among women with recent live births:
- About 23% reported smoking in the 3 months prior to pregnancy.
- Almost 11% reported smoking during pregnancy.
- More than half [54.3%] reported that they quit smoking by the last 3 months of pregnancy.
- Almost 16% reported smoking after delivery.
When comparing the ages of women who smoked:
- Women