Taking in high doses of caffeine daily during pregnancy -- whether from coffee, tea, cola, cocoa, or energy drinks -- has long been associated with an increased risk of miscarriage, and a 2008 study from the Kaiser Permanente Division of Research confirms that link. The study found that women who consumed 200 milligrams or more of caffeine per day (that's two or more cups of regular coffee or five 12-ounce cans of soda containing caffeine) had twice the miscarriage risk as women who consumed no caffeine. "It's a good idea to drink decaffeinated beverages, especially during the first trimester when the risk of miscarriage is highest," says Bridget Swinney, RD, author of Eating Expectantly.
It's best to avoid cheeses such as Brie, goat, Camembert, feta, queso blanco, and blue or other veined varieties. Why? They may be unpasteurized and contaminated with listeria -- bacteria that can trigger food poisoning. These soft cheeses have a high fear factor because they're not aged, like cheddar or Parmesan, where the process kills bacteria naturally, says Hope Ricciotti, MD, associate professor of obstetrics and gynecology at Harvard Medical School and coauthor of I'm Pregnant! Now What Do I Eat? And because pregnant women have a weakened immune system, they are more prone to certain food-borne illnesses -- which, if contracted in the first trimester, can lead to miscarriage or preterm birth.
Buying cold cuts at the deli for this week's lunches? Be careful; deli products might become contaminated with listeria if they're not handled properly at the manufacturing plant or at the deli itself. As a precaution, heat store-sliced deli meats until they're steaming-hot to kill the bacteria. And when preparing pork, beef, or lamb at home, cook it to medium or medium-well, says Dr. Ricciotti. These meats may be infected with toxoplasma, a parasite that causes an infection that, although relatively rare, can cause stillbirth or serious health problems.
You probably already know that mercury, which is present in many fish, is dangerous for your baby. "Mercury is a neurotoxin that impairs fetal brain development," says Dr. Ricciotti. When mercury from pollution gets into the water, it works its way up the food chain from plants to small fish to larger fish, leaving those big swimmers most contaminated. Fish with high levels of mercury on the don't-eat list include: shark, tilefish, king mackerel, swordfish, and albacore tuna. But not all tuna is bad. If you love tuna sandwiches, just stick to canned light tuna, which has very low mercury levels, says Dr. Ricciotti, and limit it to once or twice a week (no more than 12 ounces). A mistake some pregnant women make is to swear off all fish -- salmon, for example, doesn't contain mercury, and it's a great source of omega-3 fatty acids, which you need lots of during pregnancy. But no matter what type of fish you're eating, your best bet is to avoid anything raw or undercooked.
No one is going to tell you to avoid eggs, which are a high-quality source of protein and contain important nutrients like choline. But eggs do have some risk of being contaminated with salmonella, which is more dangerous for pregnant women than for the general population. So be sure to practice good egg safety, says Swinney: Only buy refrigerated eggs, and toss any with cracked or unclean shells. Avoid eating runny eggs (go for scrambled instead of sunny-side up), Caesar salad dressing (if it contains raw egg), unpasteurized eggnog, and homemade ice cream. And don't taste-test that raw cake or cookie batter.
The advice on alcohol is clear: In 2005, the U.S. Surgeon General issued a statement urging all pregnant women and all women who may become pregnant to avoid any alcohol consumption. The Centers for Disease Control and Prevention, too, states that there's no safe level of alcohol during pregnancy. That said, your doctor or midwife might tell you an occasional drink is harmless, and in some countries restrictions are much looser.
Know this: Alcohol crosses the placenta immediately -- you drink, your baby drinks. Women who drink frequently or heavily put their unborn baby at risk for fetal alcohol spectrum disorder, which has effects ranging from mild to severe learning disabilities, physical abnormalities, and disorders of the central nervous system. And a 2007 study at Indiana University in Bloomington found that children of mothers who drank during pregnancy had behavioral problems later in childhood.
Now that all the bad stuff is gone, here's a list of the best pregnancy nutrients -- and what to put on your shopping list.
Originally published in the September 2008 issue of Parents magazine.
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