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Alcohol and Pregnancy: Is Any Amount Safe?

Consuming alcohol during pregnancy can be a tricky decision for women, especially considering the many mixed messages on the topic
Photo by: iStock/ValuaVitaly
Does pregnancy mean giving up Pinot Noir?

Lexi Williams
Posted: October 27, 2017

When you’re expecting, your doctor will usually give you the go-ahead to indulge in a pregnancy craving every now and then. But what if it's not chocolate, pickles or even chocolate-covered pickles that you really desire after months of nausea, fatigue and unsolicited belly rubs, but a glass of Pinot Noir?

For most women, a positive pregnancy test triggers a self-imposed, total booze ban, effective immediately. But in survey results published by the Centers for Disease Control and Prevention (CDC) in 2015, roughly 1 in 10 pregnant women reported having at least one drink in the past 30 days. Are these women unaware of the risks associated with drinking during pregnancy, or is there something they know that others don't?

Drinking for Two

You've seen the government messages plastered on every drink label in the U.S., declaring the Surgeon General's warning that pregnant women should not consume alcohol. Many medical organizations, such as the American Academy of Pediatrics (AAP) and the American College of Obstetrics and Gynecologists, have taken this position as well, and physicians typically echo this recommendation when advising their patients.

This is far from just a stateside trend: In 2016, the United Kingdom Department of Health changed its stance advising pregnant women to drink no more than one to two units of alcohol once or twice a week to recommending they abstain completely. Even in countries like France, where wine is deeply embedded in the culture, lax attitudes toward maternal drinking have shifted during recent decades. Starting in 2007, producers have been required to print a health warning for pregnant women on the backs of all wine bottles, and last year, France's Ministry of Health doubled the required size of the warning in an effort to increase awareness of the dangers of drinking while pregnant.

The reasoning behind these precautions is valid. Alcohol is a teratogen, a substance that is harmful to human development. When a pregnant woman drinks, alcohol crosses the placenta and enters the bloodstream of the fetus. Because the fetus is still developing, alcohol is processed more slowly than it would be in an adult's body, causing the alcohol levels to remain high and stay in the body longer.

Exposure to alcohol in utero can lead to miscarriage, stillbirth and a range of lifelong physical, behavioral and intellectual disabilities known as fetal alcohol spectrum disorders (FASDs). While some signs of FASD are more apparent, such as severe birth defects, other, subtler symptoms include behavioral and learning problems that might arise later in a child's life.

Though the wide variety of symptoms associated with FASD make it extremely difficult to diagnose, the AAP reports that approximately 40,000 babies in the U.S. may be born somewhere on the spectrum, and that, based on reports by the CDC and other entities, anywhere between 800 and 8,000 of them may have full Fetal Alcohol Syndrome (FAS), which includes symptoms like pre- and post-natal growth problems, abnormal facial features and deficiencies in the central nervous system. A 2015 CDC report suggests that the vast variance in FAS estimates may be due to inadequate understanding and documentation of what FAS characteristics actually are.

However, much of the research on this subject is observational—researchers analyze the results of self-reported drinking by pregnant women—rather than experimental. (It's not ethical to conduct a controlled trial and ask expecting mothers to drink in the name of science.) That limits the data.

Looking at Light Drinking

Most scientific studies looking at alcohol and pregnancy focus on the dangers of binge drinking and frequent heavy drinking while pregnant, which experts across the board agree are the main culprits for FASDs and other complications. But what about occasional, light drinking?

In 2012, the British Journal of Obstetrics & Gynecology published research from five comprehensive studies that included various intelligence and behavioral tests on 1,628 Danish children, matched to their mothers' self-reported alcohol intake during pregnancy. Each study showed that the children born to mothers who drank roughly one to six 5-ounce glasses of wine per week were just as intelligent and well-developed as the children of abstaining mothers.

Another study, from Yale University, looked at the physical effects. Researchers surveyed around 4,500 pregnant women in Massachusetts and Connecticut and discovered that light to moderate alcohol consumption during the earliest and latest stages of pregnancy revealed no negative association with pre-term delivery, low birth weight or intrauterine growth restriction. The study also showed that women who drank low amounts while pregnant were less likely to have babies with low birth weight.

It's important to note that correlation does not equal causation. There are many possible explanations for these outcomes, including errors in self-reporting alcohol use, the fact that light to moderate drinkers tend to live overall healthy lifestyles and the multitude of ways in which in utero exposure to alcohol may affect a person.

In an effort to clear up some confusion, a group of researchers from the University of Bristol recently published a meta-analysis of 26 epidemiological studies (including the Yale study) that compared drinking up to 32 grams of alcohol—a little more than 2 glasses of wine—per week to not drinking at all during pregnancy. They looked at pregnancy outcomes such as miscarriage, premature birth and delivering a small-sized baby (typically babies in the lowest 10 percent weight category for their gestational age), plus longer-term outcomes such as developmental delays, impaired intellect and behavioral difficulties.

After reviewing the studies, the researchers concluded that there might be a possible link between light drinking and babies born small for their gestational age. They did not find evidence that this low level of consumption led to any other pregnancy or developmental problems.

However, the researchers pointed out that the real takeaway from the analysis was that there actually aren't many studies out there that examine effects of low levels of alcohol consumption during pregnancy. "We expected to find more studies and therefore more evidence about this level of consumption," one of the researchers, Luisa Zuccolo, told Wine Spectator via email. "This means we can neither say that it is harmful, nor how harmful it is or for which aspects of the fetus' health [and] development."

Zuccolo calls for more quality studies on the subject in order to paint a more complete picture of the subject. For now, despite the paucity of evidence for or against light drinking, Zuccolo asserts that it's better to be safe than sorry. "Our study confirms that advising women to abstain during pregnancy is indeed the safest option," she said.

Emily Oster, an author and economics professor at Brown University, sees things differently. In her book, Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong—and What You Really Need to Know, she breaks down data on confusing and controversial issues that many pregnant women face. While researching for the book—and for her own pregnancy—Oster looked at roughly 200 studies on alcohol and pregnancy and concluded there wasn't credible evidence that an occasional alcoholic beverage has any consequences.

Naturally, Oster received some pushback.

"First, there are … doctors who have expressed the view that whatever the literature says, since we know that drinking a lot of alcohol is bad, we should tell people not to drink at all. They worry that people will overdo it," Oster said via email. "Second, there are some researchers who work on this who have argued that since we do not know what a safe level is for sure, the safest option is to tell people not to drink at all."

Oster sticks to her conclusions. "It's crystal clear that drinking a lot can lead to very bad outcomes," she said. "However, I generally oppose the view that we should not expose people to the data and let them decide for themselves."

Alcohol, Before and After

The uncertainty doesn't end after you've given birth, at least not for mothers who choose to breastfeed. Studies have shown that if you have alcohol in your blood, it can be synthesized into the breast milk and passed to the baby. However, most experts agree that drinking small amounts at optimal times throughout the nursing schedule is safe.

The AAP advises that a woman who chooses to drink should do so just after she has nursed, rather than before, and to allow at least two hours per drink before the next breastfeeding or pumping session, as it takes around 30 to 90 minutes for alcohol to be absorbed into the blood stream. That way, the body has time to rid itself of the alcohol before the next feeding.

Still unsure? One 2013 study may be even more reassuring: A group of researchers from Denmark’s Odense University Hospital analyzed results from 41 publications on alcohol, nursing and infants, and concluded that, according to the study's text, "special recommendations aimed at lactating women are not warranted. Instead, lactating women should simply follow standard recommendations on alcohol consumption."

However, studies have also shown that alcohol may hinder milk production. Essentially, alcohol can inhibit the milk-ejecting reflex due to alcohol's effects on the hypothalamus. While this isn’t a reason to stop yourself from drinking if you're really craving a glass of wine, it is something to keep in mind if you're already having trouble producing milk.

Finally, some solid, good news: Moderate alcohol consumption is not believed to hurt your chances of actually becoming pregnant. A study published last year in the BMJ showed that consumption of one to seven servings a week had no effect on a woman's ability to conceive whatsoever. It also found that 14 or more servings decreased the likelihood of becoming pregnant by 18 percent, compared to no alcohol consumption at all.

But the reason most expecting mothers worry about alcohol comes during the weeks between becoming pregnant and actually finding out about it. Research shows that the first trimester, when some of the most critical development takes place, is the most vulnerable period for the fetus.

However, if you find out you're pregnant and recall having a few drinks in the past weeks, don't panic. "Most exposures prior to six weeks gestational age are all-or-none effects, where if it is a harmful exposure the pregnancy would be lost," Dr. Dibe Martin, a maternal-fetal medicine specialist and clinical professor of obstetrics and gynecology at Florida International University College of Medicine, said via email. That said, as soon as you discover you're pregnant, it's time to get serious about how you will handle alcohol going forward.

It's up to you to weigh the risks and benefits. For some, even the slightest possibility of harming their unborn children is enough to keep them dry for nine months. ("Why take the risk?" the CDC website asks.) For others, an occasional drink may help them maintain a small semblance of normalcy during a physically and emotionally taxing period in their lives.

While there will likely be mixed messages on this topic for years to come, one thing's for sure: Staying informed on the latest research and recommendations will allow you to make the right choice for yourself and your future baby, and should motivate you to respect the decisions of other soon-to-be-parents, as well.

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