A new study suggests that drinking alcohol during pregnancy can be most dangerous during the second half of the first trimester, from about 6-13 weeks.
In the study, which involved nearly 1000 participants, more alcohol during pregnancy in general raised the odds of abnormally shaped lip or altered eye appearance, smaller head size, and low birth weight, all early signs of fetal alcohol syndrome. But for every drink per day increase during the second half of the first trimester, a mother’s baby was 25% more likely to have these symptoms.
Dr. Christina Chambers of the University of California, San Diego said, “this supports the surgeon general’s recommendation that drinking be avoided entirely.” She added that there’s no known threshold below which alcohol is safe.
This study doesn’t surprise me. I’ve always read that from about 5 week to the end of the first trimester the embryo is particularly vulnerable to toxins.
But studying alcohol in pregnancy is tricky. There are lots of variables for one thing: “Even if you find 10 women who drink a quart of vodka a day, maybe only five of those babies will have full-blown fetal alcohol syndrome, because there are other factors that influence the risk,” said Dr. Chambers. Some of these factors include body fat levels, genes, diet, and other environmental exposures. It’s also hard to do research on this topic as women have to “self-report” alcohol consumption so data is not always so accurate.
This new study involved interviews with women consistently and periodically and therefore, the authors claim, carries some extra weight. The study involved almost 1000 infant/mothers pairs. All the mothers in the study, at some point between 1978 and 2005, called a hotline set up to field questions about substances that can be harmful during pregnancy. Mothers answered questions over the phone about their alcohol consumption during pregnancy. The infants of these mothers were evaluated at birth. And there were follow-up interviews.
The study also found that increased alcohol in the second trimester raised the odds of an upper lip abnormality. But increased number of drinks in the third trimester only affected length at birth. Interestingly binge drinking– more than 4 drinks in one session– did not correlate with increased risk but total number of drinks consumed over the whole pregnancy did.
The bottom line? The more you drink, the more risk of adverse outcomes and drinking during the end of the first trimester is especially risky.