Researchers have proven that alcohol is toxic to the fetus, although exactly how alcohol causes damage is not fully understood. Alcohol can harm fetal cells. It also affects the placenta, the organ through which the fetus absorbs oxygen and nutrients from the mother, reducing the blood flow to the fetus and causing a severe shortage of oxygen.
The extent to which a fetus is damaged by exposure to alcohol depends on when the mother consumed alcohol during her pregnancy, and how much alcohol she consumed, among other factors. Studies of pregnant animals that were fed alcohol have led researchers to conclude that major physical defects in the human embryo, the early developing organism, can be caused by exposure to alcohol in the first trimesteróthat is, the first three months of pregnancy. Decreased fetal growth is associated with exposure to alcohol in the third trimester. Brain damage can result from exposure of the fetus to alcohol at any point during the pregnancy.
Researchers know that the more alcohol the mother drinks and the longer the fetus is exposed to the motherís alcohol consumption, the more severe will be the childís birth defects. Binge drinking, or heavy alcohol consumption at one sitting, is particularly hazardous to the fetus, because very high levels of alcohol enter the motherís blood stream, and the alcohol is passed into the blood of the fetus through the placenta.
The United States surgeon general recommends that women stop drinking alcohol entirely during pregnancy. Women who are trying to become pregnant, or who suspect they are pregnant, are urged to stop using alcohol in order not to damage the developing embryo.