Many factors can affect the development of a fetus. Environmental agents that can negatively affect prenatal development are called teratogens. Teratogen exposure tends to be most detrimental during the first trimester (the first three months) of pregnancy, when formation of the organs and brain occurs. However, some substances, such as alcohol, can have an effect at any point in pregnancy.
Alcohol consumption can harm a developing embryo or fetus, although how much is too much remains unclear. "The only way to be absolutely certain that your baby is not harmed by alcohol is not to drink at all during pregnancy or while you are trying for a baby," says the Royal College of Obstetricians and Gynaecologists (RCOG). Pregnant women who continue to drink are at increased risk of experiencing a miscarriage or stillbirth. Infants exposed to alcohol before birth may show signs of Fetal Alcohol Spectrum Disorder (FASD), including learning problems, behavior problems and physical disabilities, the RCOG reports. Fetal Alcohol Syndrome, which results in mental retardation and facial abnormalities, is uncommon. Unlike FASD, which can occur with only moderate exposure to alcohol, Fetal Alcohol Syndrome only occurs due to heavy drinking during pregnancy.
At least 10 percent of American pregnant women smoke, according to the March of Dimes. These statistics are concerning, since smoking during pregnancy greatly increases the risk of low birthweight and prematurity. Both conditions put a newborn at risk for early complications, including respiratory distress and possible death, and are associated with later health and learning issues. Fortunately, pregnant women can choose to stop smoking during their preganncy and vastly decrease the risks. In fact, "If a woman stops smoking even by the end of her second trimester of pregnancy, she is no more likely to have a low-birthweight baby than a woman who never smoked," says the March of Dimes.
Drugs, whether illegal, over-the-counter or prescription, can affect prenatal development. Illegal drugs like cocaine, heroin and methamphetamine have been associated with increased risks of miscarriage, prematurity and low birthweight. The infant may also be born addicted to the drug, according to the American Council for Drug Education (ACDE). Medications that may be harmful to fetal development include aspirin, ibuprofen, anticonvulsants and many antimigraine drugs, the ACDE reports. If you are pregnant, all medications and herbs should be cleared by your doctor before use.
Many diseases, some of them relatively common, can disrupt healthy development of the fetus. For example, if a mother comes down with measles (rubella) or chicken pox (varicella) while pregnant, birth defects including blindness, mental retardation and malformed limbs may result, says the March of Dimes. If you are planning to become pregnant, your doctor can perform bloodwork to see if you are immune to these diseases. If you are not immune, you can be given an immunization. It is too late to immunize once you are pregnant.