Alcohol is a known toxin that crosses the placenta to a growing fetus during pregnancy. Drinking alcohol during pregnancy can have devastating effects on the fetus and cause complications with the pregnancy itself. Drinking in early pregnancy, while the major organs are forming, is most harmful to the fetus, but drinking at any stage can have consequences and is the leading cause of birth defects, the Merck Manual warns.
Incidence
Alcohol use during pregnancy is not uncommon, despite the known fetal risks. The March of Dimes states that approximately one in 12 women in the United States drink during pregnancy and that one in 30 report at least one episode of binge drinking, defined as five or more drinks on any one occasion.
Fetal Transmission
Alcohol passes to the fetus through the placenta. Fetal and maternal blood vessels lie very close together in the inner spaces of the placenta, with only a thin membrane between them, so that nutrients and waste products can be passed between the two. Alcohol easily passes across this membrane into the fetal blood, the Merck Manual explains.
Fetal Consequences
The fetal consequences of alcohol use are many. Miscarriage rates are nearly double in those who drink during pregnancy. Drinking more than five drinks a week or binge drinking during the first 16 weeks of pregnancy also increases the risk of stillbirth by 56 percent or more, according to the March of Dimes. Alcohol is also responsible for one in six cases of cerebral palsy and 10 percent to 20 percent of mental retardation, pediatrician and columnist Alan Greene, M.D., explains.
Alcohol use during pregnancy also can cause fetal alcohol syndrome (FAS), which is identified by distinct facial features, growth retardation and central nervous system (CNS) abnormalities, including learning disabilities, attention deficit disorders and abnormal brain structure.
Children with the CNS effects of alcohol exposure and effects on other organs, such as the bones, eyes, heart and liver, but without the characteristic facial features, are said to have alcohol-related birth defects, or ARBD. This type of damage is associated with drinking in the first 12 weeks of pregnancy, the March of Dimes notes. Alcohol-related neurodevelopmental disorders, or ARND, describes those born with the CNS effects only.
Maternal Risks
Women who drink during pregnancy have an increased risk of placental abruption, a condition in which the placenta prematurely separates from the uterine wall, Beth Israel Deaconess Medical Center warns. Placental abruption can cause maternal or fetal hemorrhage and death. Premature delivery also can occur, putting the newborn at risk for complications such as cerebral palsy, respiratory problems and death.
Safe Limits
While women who binge drink or who drink more than seven drinks a week are most likely for FAS, no safe levels exists for alcohol consumption in pregnancy. As little as one drink a week during pregnancy has been associated with physical and behavior abnormalities, according to the March of Dimes.
