Here's What Does—and Doesn't—Cause Miscarriage

Can stress cause a miscarriage? What about sex, exercise, or certain foods? We spoke with experts to break down common myths about the causes of pregnancy loss. 

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About 15-20% of known pregnancies end in miscarriage, according to the American College of Obstetricians and Gynecologists (ACOG). But it might be reassuring to know that by the time you see a heartbeat on an ultrasound—usually by week six or seven—your chance of having a miscarriage drops to less than 5 percent, regardless of your age, says Michael Lu, M.D., associate professor of obstetrics and gynecology at the University of California, Los Angeles.

Despite how common miscarriages are, many women are surprisingly in the dark about what actually triggers them, according to research from Ohio State University College of Medicine. "Much misinformation is shared among women or passed down from older generations," says Jonathan Schaffir, M.D., an assistant professor of obstetrics and gynecology at Ohio State University College of Medicine, who authored the study.

Here’s what you need to know about what does—and doesn’t—cause miscarriage.

What Actually Causes Miscarriages

Up to 70 percent of first trimester miscarriages and 20 percent of second trimester miscarriages occur because of a glitch in the fetus's genes, according to the March of Dimes. "When the chromosomes of the egg and those of the sperm fuse to form an embryo, they usually pair up correctly," says Henry Lerner, M.D., an OB-GYN at Newton-Wellesley Hospital in Newton, Massachusetts. "But sometimes they get scrambled; if they're paired incorrectly, the embryo stops developing." It doesn't mean that anything's wrong with the mother or father. Plus, you're unlikely to repeat a chromosomal error the next time you conceive, so don't assume the past predicts your future.

Another cause of miscarriage is certain illnesses, especially those that restrict blood flow to the uterus like diabetes, thyroid disease, lupus, and heart disease, as well as others like uterine infections. Hormonal imbalance and excess caffeine intake may also play a role. Indeed, women who consumed 200 milligrams or more of caffeine each day (about two cups of regular coffee or five 12-ounce cans of caffeinated soda) had twice the miscarriage risk as those who didn't have any, according to a study by Kaiser Permanente in the American Journal of Obstetrics and Gynecology.

Finally, excess drug and alcohol use can lead to miscarriage. "Exposing a fetus to large amounts of these chemicals on a regular basis that can cause miscarriage, because they have a poisonous effect on all those developing cells," says Dr. Schaffir.

What Doesn't Cause Miscarriage: Debunking Common Myths

We asked Dr. Schaffir to debunk some major misconceptions about miscarriages. "It's important for women to understand that these are just old wives' tales—and not only are they not true, but in some cases, believing them can affect your health and wellbeing," he says.

Can Exercise Cause Miscarriage?

Exercising or picking up a (reasonably) heavy object—a grocery bag, a toddler, or the like—are extremely unlikely to cause a miscarriage. In fact, most experts agree that exercise during pregnancy, with your doctor’s approval, can lower miscarriage risk and make mom and baby healthier. That’s because exercise reduces stress, relieves aches and pains, lowers your gestational diabetes risk, and even builds up stamina for labor.

Can Stress Cause Miscarriage?

While some studies on stress and miscarriage are conflicting, Dr. Schaffir says that everyday tension or anxiety—tight deadlines at work or worrying about what labor will be like—has not been linked to pregnancy loss. What’s more, no studies have ever linked excessive bad moods to miscarriage, says Dr. Schaffir.

Things get murky when dealing with major stress, though. "We're talking big things, like the death of a spouse or parent," he explains, and even then, the link is not well established. Plus, women under extreme stress are also more likely to smoke, drink, or do drugs, which can affect miscarriage.

Can Food Cause Miscarriage?

Pregnant women should maintain a healthy and nutritious diet throughout pregnancy. While foods themselves don't cause miscarriage, certain items increase the risk for food-borne illnesses like listeria. Severe cases of listeria have been linked to miscarriage and pregnancy complications. You should avoid, for example, raw meat and fish, soft cheese, unpasteurized cheese, and deli meat; check out this article for more information.

Can Sex Cause Miscarriage?

Experts have deduced that there is no link between miscarriage and sex—even though intercourse might sometimes feel uncomfortable due to your changing body. So feel free to get intimate with your partner while expecting!

Could Miscarriage Be Mom's Fault?

The vast majority of miscarriages occur because of chance chromosomal or genetic abnormalities in the unborn baby or, less commonly, hormonal imbalances or problems with the uterus or placenta, says Dr. Schaffir. These factors are nothing that a mom-to-be has control over. “It's natural for a woman experiencing loss to try to explain it in some way, even if that means blaming herself," he says. "But all women need to know that most of the time, a miscarriage is completely random, and odds are you will get pregnant after trying again."

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