(iStock/Pregnant women can breathe easy: Complicated diets and prenatal vitamins aren’t necessary for a healthy pregnancy. )
Amy Tuteur is an obstetrician-gynecologist and former clinical instructor at Harvard Medical School and the author of "Push Back: Guilt in the Age of Natural Parenting."

Pregnancy has never been safer — a good reason for parents and children everywhere to celebrate on Mother’s Day. Ironically, as major risks have receded into the past, minor risks have taken center stage. Pregnancy often feels like a minefield: Watch what you eat, watch how you exercise, watch what you do. But many of these worries are based on myths. Here are five of the most stubborn.

Myth No. 1
Prenatal vitamins are necessary for healthy pregnancies.

What to Expect, the website affiliated with the famous pregnancy advice book, explains prenatal vitamins as “an insurance policy, offering you the security of knowing that your body is stocking up on the most essential baby-making vitamins it needs to conceive and nourish your baby-to-be through a healthy pregnancy.” BabyCenter, a popular parenting website, answers the question “Are prenatal vitamins really necessary?” with a solid “Yes.”

Where did we get the idea that big, expensive multivitamins are necessary for a healthy pregnancy? As with so many aspects of nutrition in pregnancy, researchers studied women from developing countries, often women who were severely nutritionally deprived. Not surprisingly, for women who are chronically malnourished and lacking essential vitamins and nutrients, prenatal supplements can make a difference. Yet that does not mean they’re necessary for women who already eat all the vitamins and minerals they need.

For women who aren’t malnourished, nearly every vitamin and mineral contained in those bulky pills (with the exception of folate and iron) appears to have no impact on pregnancy outcomes. Since folate and iron are each available on their own, there’s no need to take a huge, often nauseating prenatal vitamin, which does little more than give women expensive urine.

Myth No. 2
Pregnant women must monitor their diets carefully.

An Amazon search for books on the proper pregnancy diet turns up page after page with titles like “What to Eat When You’re Pregnant: A Week-by-Week Guide to Support Your Health and Your Baby’s Development” and “Eating for Pregnancy: The Essential Nutrition Guide and Cookbook for Today’s Mothers-to-Be.”

Despite alarming articles warning against foods from coffee to chicken wings, elaborate dietary rules aren’t necessary. Myriad studies show that nutritional changes can help women who are malnourished, but eating specific foods in specific quantities appears to have no effect on pregnancy outcomes in industrialized countries. There’s no evidence that fad diets, restrictive diets or the Brewer diet, in which alternative-health practitioners advise a complicated regimen of 14 different categories of food daily, have any impact on the health of the baby or the incidence of complications.

The most important guidance for pregnant women in the United States involves foods that can transmit illnesses; that’s why women should avoid undercooked meats and raw dairy products. But there is no evidence that small amounts of caffeine affect unborn babies. Studies on alcohol are more ambiguous. Although it is quite clear that large amounts of alcohol can cause fetal alcohol syndrome, the limit of safe consumption is unknown. There are some doctors who insist that if we don’t know the exact limit, women should avoid any alcohol. But most believe that an occasional glass of wine or beer will not cause any problems.

Myth No. 3
Bed rest can prevent miscarriage.

According to Natural Fertility Info, one of the oldest alternative-medicine advice sites about pregnancy, “Bed rest and removal of stress factors is the most important first step to take” to prevent miscarriage. And the University of Maryland Medical Center points out that “your physician may also prescribe bed rest” in hopes of preserving a pregnancy.

Miscarriage is not a rare experience: Up to 20 percent of pregnancies will naturally end that way. The most common cause is a serious genetic abnormality. In some cases, the fertilized egg divides and grows for a period of time but eventually dies. In many cases, no fetus develops, only placental tissue. So nothing can prevent most miscarriages: Those pregnancies are doomed from the moment of conception.

More broadly, studies have found that bed rest does not change a woman’s chances of having a miscarriage. So why did doctors start recommending bed rest to reduce miscarriages? It’s not because there was ever high-quality scientific evidence to support it. At most, it seemed like a harmless recommendation — a way for women to feel that they were doing something to preserve the pregnancy, though benefits in the first trimester are usually limited to peace of mind.

Myth No. 4
Pregnant women should not have X-rays.

Fit Pregnancy, a popular health website, promises to teach women “how to protect your baby from the unseen dangers of X-rays,” while Britain’s National Health Service warns that “if possible, you should avoid having an X-ray while you’re pregnant.” Health advice forums are awash with mothers anxiously wondering if it’s safe to go in for an X-ray.

Like any medical procedure, X-rays carry risks, whether one is pregnant or not. But as the Mayo Clinic notes, having an X-ray while pregnant usually poses no danger to the developing fetus. And addressing a mother’s health issues could be vitally important to both her and her child.

After all, the baby is not the only patient in pregnancy; the mother is an equal (if not more important) patient. If a woman develops a health problem that requires X-rays, medications or surgery to diagnose and treat, that problem should be addressed. Untreated maternal medical issues are not merely dangerous for the mother. If they are serious enough, they can lead to miscarriage, premature labor or stillbirth. So treating the mother is also in the baby’s interest.

Myth No. 5
Pregnant women should avoid vaccinations.

Alternative-medicine practitioners and those selling “natural” health advice often tell women to avoid being vaccinated while pregnant. Green Med Info, for instance, warns readers of “the deadly truth about flu vaccines and pregnancy.” Kelly Brogan , a “holistic women’s health psychiatrist,” counsels her readers on “following your inner compass” and “rejecting flu vaccine in pregnancy.”

It’s best to make sure you are fully up to date on your vaccinations before you become pregnant, since some vaccines (like the mumps, measles and rubella (MMR) and varicella vaccines) do pose risks during pregnancy. But others are safe, such as those for tetanus, flu and pertussis (whooping cough).

In fact, the pertussis vaccine also protects babies after birth. Whooping cough is one of the greatest infectious threats to infants. With the recent resurgence of the disease because of under-vaccination, babies younger than 6 months (and therefore not fully vaccinated) face serious risks.

We’ve always known that mothers can pass whooping cough antibodies across the placenta . Immunizing or re-immunizing women in the third trimester boosts the production of maternal antibodies, thereby increasing the antibodies their babies get. This can dramatically reduce the risk of an infant contracting whooping cough, with its high incidence of serious complications and death. Pertussis vaccine is recommended for every pregnant woman in every pregnancy.

outlook@washpost.com

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