Alcohol in Pregnancy
Abstract & Commentary
By John C. Hobbins, MD
Professor, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora
Dr. Hobbins reports no financial relationships relevant to this field of study. This article originally appeared in the December 2013 issue of OB/GYN Clinical Alert.
Synopsis: Data collected from a large study involving four countries show no effect of alcohol exposure in varying degrees on the rate of preterm birth, low birth weight, average birth weight, and preeclampsia.
Source: McCarthy FP, et al. Association between maternal alcohol consumption in early pregnancy and pregnancy outcomes. Obstet Gynecol 2013;122:830-837.
A 2011 american college of obstetricians and gynecologists (ACOG) Committee Opinion gave "compelling and clear advice to avoid alcohol" in pregnancy and prior to pregnancy.1 Yet the Centers for Disease Control and Prevention (CDC) indicates that about 50% of women in the United States admit to some intake of alcohol in pregnancy.2 Since the data are inconsistent regarding how much alcohol affects the fetus, even in higher dosage, the Royal College of Obstetrics and Gynecology has taken a less conservative approach by saying that harm is unlikely to occur from one to two units of alcohol consumed once or twice per week.3 However, the Royal College strongly advises against binge drinking.
In an effort to see if alcohol consumption in varying amounts has an effect on some easy-to-track outcomes, a multicenter study was undertaken in four countries: Great Britain, Ireland, New Zealand, and Australia — the Screening for Pregnancy Endpoints (SCOPE) study.4 Outcome data were available on 5628 patients who were enrolled between 2006 and 2011. Patients were screened for alcohol consumption immediately prior to, and/or during, the first 15 weeks of pregnancy. The amount of exposure was quantified as follows: one unit of alcohol represented 10 mL of pure alcohol, which was equivalent to one shot of whiskey, a half a glass of wine, or one small glass of beer. Bottled mixed drinks each contained two units. Binge drinking meant that more than six units were consumed per drinking session.
The timing of alcohol exposure was broken up into four groups: 1) abstinent throughout this period, 2) none prior to conception, 3) quitting before 15 weeks, and 4) drinking throughout this window of time. Binge drinking was tracked according to these time intervals.
Based on the CDC data, the alcohol consumption statistics were not surprising. For example, 40% reported no alcohol consumption in pregnancy, 19% admitted to "occasional" intake (1-2 units per week), 25% were in the "low" category (3-7 units per week), 11% were "moderate" drinkers (8-14 units per week), and 5% were in the "heavy" group (> 14 units per week). Thirty-four percent said there was exposure to alcohol during the first 3 months and 23% admitted to at least one episode of binge drinking. It is important that the authors attempted to account for the many confounding variables, including smoking, when evaluating the results.
The authors studied four outcomes: birth weight, small for gestational age (SGA), spontaneous preterm birth, and preeclampsia. After adjusting for confounding variables there were no differences between groups regarding average birth weight, low birth weight, or the rates of SGA or preeclampsia. Even binge drinkers did not display differences in these categories and the timing of alcohol exposure had no effect on any of these endpoints.
Simply put, the timing and amount of alcohol consumption before and during early pregnancy seemed to have no effect on any of the four outcomes evaluated.
Often patients have been referred to us for ultrasound evaluations because they consumed alcohol in varying amounts early in pregnancy. The majority have not been hard-core drinkers and many were in the restaurant business where it is common for employees to gather at the bar for a few pops (or more) before heading home. Since the admonition to abstain from alcohol in pregnancy is well entrenched in the United States, these women were frightened out of their wits when they suddenly found themselves pregnant. This study suggests that their possible concerns, at least for preterm birth, growth restriction, and preeclampsia, can be allayed. On one hand, since alcohol consumption in large amounts during organogenesis can be a teratogen (the face and heart) and has the capability later in pregnancy to affect the central nervous system (as in fetal alcohol spectrum disorders), it would not be advisable to advocate a carte blanche approach to drinking in pregnancy, and obviously avoiding any alcohol is the best way to avoid any effect. On the other hand, since thus far there are no conclusive data to link modest intake with fetal effect, it is very unlikely that an occasional drink would have an adverse effect.
Many years ago, we tried to correlate alcohol intake in pregnancy with in utero brain findings on ultrasound, as well as with one specific measure of neurological performance in infants.5 We found that abnormal neurological results correlated with frontal lobe size, which, in turn, correlated with alcohol intake. However, this relationship was significant only when there was heavy consumption (six drinks or more per day). Interestingly, no infant in the study, even in the high consumption group, displayed the constellation of stigmata necessary to document alcohol's most devastating effect — fetal alcohol syndrome.
The story gets more complicated on the maternal side when one delves into the genetics of vulnerability to alcohol addiction and the varying abilities of individuals to metabolize alcohol, and, obviously, on the fetal side there is much more to learn about alcohol's variable effects. Not surprisingly, the topic of alcohol in pregnancy is controversial and has brought out a full spectrum of hawks and doves (and last time I wrote about this I got flack from both sides). As indicated in the ACOG committee opinion, abstaining is a foolproof way to ensure that a fetus will not be affected. However, it also seems reasonable to tell women who have had some inadvertent exposure to alcohol in early pregnancy that it is unlikely to have had a major effect on their fetuses — with the caveat that it is time to either stop or keep their consumption to an occasional glass of an alcoholic beverage once or twice a week from that point on, as articulated by the British College.
- American College of Obstetricians and Gynecologists; Committee on Health Care for Underserved Women. Committee opinion no. 496: At-risk drinking and alcohol dependence: Obstetric and gynecologic implications. Obstet Gynecol 2011;118(2 Pt 1):383-388.
- Centers for Disease Control and Prevention (CDC). Alcohol use and binge drinking among women of childbearing age — United States, 2006-2010. MMWR Morb Mortal Wkly Rep 2012;61:534-538.
- Royal College of Obstetricians and Gynaecologists. Available at: http://www.rcog.org.uk/files/rcog-corp/uploaded-files/RCOGStatement5AlcoholPregnancy2006.pdf. Accessed October 25, 2013.
- McCarthy FP, et al. Association between maternal alcohol consumption in early pregnancy and pregnancy outcomes. Obstet Gynecol 2013;122:830-837.
- Wass TS, et al. The impact of prenatal alcohol exposure on frontal cortex development in utero. Am J Obstet Gynecol 2001;185:737-743.