Many women wonder, when faced with the thought of conceiving or the possibility of pregnancy, whether they can continue to drink alcohol. Further, even women who plan to abstain from all alcohol during pregnancy are occasionally surprised by a missing period, and worry that during the weeks they were pregnant and unaware, they drank alcohol. Particularly because the first trimester is the one during which the bulk of organ formation takes place, it's an especially sensitive period, and it's worth knowing a little bit about the potential effects of alcohol during that time.
Alcohol is a toxin. While adults grow accustomed to--and even enjoy--its effects, the faint sense of dissociation associated with small amounts of alcohol is a sign of its ability to impair brain function, even in small doses. While many chemicals taken internally by women during pregnancy are unable to pass to the fetus because of the protective power of the placenta, alcohol is a very small molecule and easily passes from mother to baby. As a result, alcohol concentrations in the fetus quickly reach the same levels as those of the mother.
In his book "What You Didn't Think to Ask Your Obstetrician," Dr. Raymond Poliakin notes that alcohol has a number of potential effects. In the first trimester, a sensitive period with regard to the viability of the pregnancy under even the best of circumstances, alcohol consumption is associated with increased risk of miscarriage. Assuming that the pregnancy lasts, however, alcohol introduces the potential for serious birth defects. Fetal alcohol syndrome, a set of symptoms including poor coordination and sleep, low IQ, developmental delays and characteristic facial features, is often seen in babies whose mothers drank early in and throughout pregnancy.
Of course, many women know that alcohol can damage an unborn baby, and plan to abstain once they're pregnant. These women may become concerned if they learn of a pregnancy, only to realize that they consumed alcohol after conception and before knowing they were expecting. In "What To Expect When You're Expecting," authors Heidi Murkoff and Sharon Mazel comfort women with the assurance that it's quite difficult to harm a very early embryo with alcohol, as the embryo doesn't implant--and therefore isn't connected to maternal blood supply--until approximately two weeks after conception. As such, most women become aware of the pregnancy right around the time that the embryo becomes susceptible to alcohol damage.
Murkoff and Mazel do recommend that women who are planning to become pregnant limit their alcohol consumption or stop drinking entirely. While it's unlikely that alcohol consumed before a woman knows she's pregnant will damage a baby, it's best to take the safest approach possible, particularly if a woman is actively trying to conceive. They also note that alcohol contains calories that are devoid of nutrition, and since nutrition is important both before and after conception, replacing alcohol calories with more nutritious choices helps ensure a healthy pregnancy.
Some women choose to drink alcohol during the first trimester, and throughout pregnancy, on the grounds that there's very little research demonstrating negative effects of moderate alcohol consumption on a fetus. In fact, this is simply because it's not possible to conduct medical research on pregnant women, so it has been difficult for doctors to draw strong scientific conclusions regarding safe levels of alcohol consumption. As such, most doctors risk erring on the side of caution, and while many women deliver healthy babies despite moderate alcohol consumption during the first trimester, medical professionals generally advise abstinence.