Pregnancy and Alcohol – How much is safe?
We often have pregnant patients ask us if an occasional glass of wine with dinner is safe. While it is well accepted that fetal alcohol syndrome (FAS) is often the result of chronic daily alcohol use or occasional binge drinking, the adverse effect of moderate alcohol consumption on the developing fetus is more controversial. FAS is a spectrum of physical and neurologic abnormalities that result from heavy maternal alcohol consumption. Alcohol readily crosses the placenta and can permanently damage the developing brain and cause dysmorphic and stunted development. In the United States, it is estimated to affect 0.2 to 2 children per 1000 births. Tragically there are some areas in the U.S. where as many as 5% of children are affected.
How much is too much?
One unit of alcohol is equivalent to 8 grams of absolute alcohol and can be obtained with any of the following:
- 1/2 pint of regular beer
- 1/4 pint of strong beer
- One small glass of wine
- One single measure of spirits
- One small glass of sherry
Several extensive studies in the 1990’s concluded that there were no adverse effects on pregnancy outcome with consumption of less than 120 grams or 15 units per week. These conclusions led to the recommendations by the national health service of several countries to condone low-level alcohol consumption in pregnancy. In Australia, the 2001 guidelines published by the National Health and Medical Research Council (NHMRC) state that “women who are pregnant or might soon become pregnant” should limit their alcohol consumption to fewer than seven standard drinks per week and no more than two standard drinks on any one-day. The United Kingdom’s Royal Society of Obstetrics and Gynecology (RCOG) as well as the National Institute for Health and Care Excellence (NICE) position at the time stated that while abstinence was safest, 1–2 standard units of alcohol once or twice a week for pregnant women was acceptable. Ireland had no concrete recommendations other than to “cut down” on alcohol consumption and avoid binge drinking. Canada also had no specific guidelines other than to state that the risk from low-level alcohol consumption is minimal. Only New Zealand and the US recommended complete abstinence of alcohol consumption for pregnant women or those attempting pregnancy. In contrast, the CDC, U.S. Surgeon General, American College of Obstetricians and Gynecologists, and the American Academy of Pediatrics have always recommended complete abstinence from alcohol consumption during the entire pregnancy and only minimal intake during breastfeeding. Currently, the American Academy of Pediatrics recommends that breastfeeding mothers consume no more than 0.5 gram of alcohol per kilogram of the mother’s body weight, which is the equivalent of 2 ounces of liquor, 8 ounces of wine or 2 beers for a 132-pound woman. In order to minimize the amount of alcohol passed to the baby, they recommend not breastfeeding or pumping for at least two hours after having a drink.
The adverse effects of the moderate consumption of alcohol in pregnancy remain controversial. Recent studies have demonstrated an increased risk of neurodevelopmental problems and preterm birth following in utero exposure of as little as 30–40 grams of alcohol per instance and as little as 70 grams of alcohol per week. This amount is equivalent to approximately 2 to 2.5 servings of wine or full-strength beer once or twice per week. In addition, Magnetic Resonance Imaging (MRI) studies have shown that prenatal alcohol exposure can affect a number of regions of the brain involved in verbal communication development. This exposure manifests itself through physical changes in the brain’s structure including displacing, producing shape variability, or reducing the volume, area, and length of the corpus callosum.
This week the RCOG and NICE made news with a reversal of their position on alcohol use in pregnancy. They now state that abstinence is the only way to be sure that the fetus is unharmed and that there is no proven safe amount that women can drink during pregnancy. The RCOG also emphasizes that the time around conception and the first three months of pregnancy are the riskiest periods for alcohol exposure, and thus they recommend abstinence during this time.
However, contrary to the CDC, the RCOG guidelines continue to state:
“Drinking small amounts of alcohol after this time does not appear to be harmful for the unborn baby, but you should not:
- drink more than one or two units, and then not more than once or twice per week
- binge drink (which for a woman is when she has six units or more of alcohol on any one occasion).”
Concerning breastfeeding, the RCOG states:
“You should not drink more than one or two units, more than once or twice a week.”
These conflicting guidelines continue to generate a lot of controversies. It seems prudent for women to follow the US guidelines of complete abstinence – If there is the smallest chance of harming your child, is a drink worth the risk?
A note of caution for health care providers regarding the communication of the risks of alcohol consumption so as, not to panic new mothers to be. As many as one-half of all pregnancies are not planned, and it is not uncommon that women will have unwittingly consumed alcohol early in pregnancy. While it is important that women understand the need to avoid alcohol, the risk to the individual will be relatively small in most cases. Fetal development is a complex process and clearly, the best choice is to avoid all known risk factors.
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