Does Obesity Cause Miscarriage?

Cheerful overweight couple expressing romance in nature; pregnant obesity

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In recent decades, scientists have devoted a great deal of research to investigate the link between obesity and miscarriage, and it seems fairly clear that weight plays a key role.

But does obesity in and of itself cause miscarriage? It's a question that many doctors, scientists, and women at risk struggle with, often blurring the line between what the research tells us and what we assume it to mean.

What the Research Says

From a research perspective, obesity—defined as a body mass index over 30—is associated with an increased risk of pregnancy complications, including miscarriage and recurrent miscarriage (as well as an increased risk of difficulty conceiving in the first place). Research also suggests that losing weight may reduce the risk of miscarriage in obese women, even among those with a history of miscarriage.

Many of the studies have involved women with polycystic ovary syndrome (PCOS), a condition in which women are more likely to be overweight. Even among this cohort of women, there was a clear association between levels of weight loss and rates of miscarriage.

As a result of these and other pieces of evidence, the American College of Obstetricians and Gynecologists (ACOG) currently recommends that doctors offer nutritional counseling for obese women who are planning a pregnancy.

Link Between Obesity and Miscarriage

While there is an association between obesity and miscarriage, it's important to remember that the majority of women who are overweight do not have miscarriages. Moreover, like women of normal weight, obese women who have had a miscarriage usually go on to have a successful subsequent pregnancy.

The most likely explanation of the link is that obesity compounds the risk of other factors associated with pregnancy loss. For example:

  • Obesity is associated with high blood pressure, which can complicate preeclampsia.
  • Obesity can make diabetes harder to manage, increasing the risk of complications in the first 13 weeks.
  • Obesity can compound a difficult situation in women with PCOS, who already run a higher risk of miscarriage.

Managing Weight During Pregnancy

While experts recommend losing weight prior to pregnancy, you can’t always control when you get pregnant. If you get pregnant unexpectedly or before you reach your goal weight, meet with your obstetrician to determine a healthy pregnancy weight gain for you.

If your BMI is 30 or more, the Institute of Medicine (IOM) recommends gaining no more than 15 to 25 pounds during the entire pregnancy, with a rate of 0.5 pounds per week in the second and third trimester.

Your best bet is to work closely with your obstetrician throughout your pregnancy to manage your weight in a way that protects you and your baby.

Losing Weight to Lower Your Risk

Reaching a healthy weight is the best way to decrease the risk of miscarriage. According to ACOG, losing 5% to 7% of body weight (or 10 to 20 pounds) can improve overall health and your chances of a healthy pregnancy.

Seek Professional Help

If you're obese and thinking of having a baby, your first step should be to talk to your doctor who can do a complete physical, including testing you for insulin resistance, PCOS, and thyroid imbalances, which can also contribute to fertility problems.

Your doctor can help advise you on the best way to lose the weight and may even recommend a nutritionist, who can help you create a plan for safe weight loss.

Emphasize a Healthier Lifestyle

Approach weight loss as a means of a healthier lifestyle rather than pinning your efforts to a specific number of pounds or dress sizes. By doing so, weight loss becomes part of an ongoing process instead of an event that starts and ends. Yes, there will be ups and down, but like motherhood itself, it's about the slow-and-steady over the here-and-now.

Say No to Crash Diets

Avoid crash diets and rapid weight loss programs, which may impede your ability to conceive by undermining the quality of your eggs. Losing weight slowly and in a healthy way is best for your fertility and your overall health.

Avoid the Blame Game

If you're overweight and have suffered a miscarriage, resist the temptation to blame yourself. Sadly, miscarriage can happen to anyone. What's more, being overweight might not be the only reason you're having trouble conceiving.

According to a report from ACOG, the rate of miscarriages in the United States, irrespective of weight, can run from anywhere from 17% in women under 30 to upwards of 40% by the time you reach 40.

A Word From Verywell

Pregnancy loss can happen for a variety of reasons that are beyond your control. With the right support, you can manage your weight, pay extra attention to diet and exercise, and seek regular prenatal care to reduce your risk of miscarriage due to obesity.

Weight loss is never easy, but the hard work will be well worth it as you begin to feel stronger, healthier, and more energetic and increase your odds of starting a family.

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