Fertility and pregnancy sometimes depend on hormones, biology, timing, and luck. With so many elements affecting a person’s ability to get pregnant and deliver a healthy kid, it’s tempting to blame others. Obesity increases such pressure.

Obesity commonly causes infertility, according to study. The American Society for Reproductive Medicine reports that 6% of never-pregnant women have reproductive issues due to obesity. Obesity lowers semen quality, decreasing male fertility.

According to Christina Boots, M.D., an associate professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine in Chicago, obesity may make it harder to have children. Dr. Boots explains, “There is good data that shows the higher a person’s BMI (body mass index), the lower their success rate at achieving a healthy pregnancy.”

Obese women had irregular menstrual periods, more miscarriages, and worse IVF success rates. She adds, “BMI is a predictor of health—but it’s an oversimplified predictor. Fertility is more complicated than a link.”

Obesity and Infertility

According to the Society of Reproductive Surgeons, 6.7 million American women—11% of the reproductive-age population—are infertile. Infertility affects men and women.

According to the Centers for Disease Control, age, smoking, excessive alcohol use, higher physical or emotional stress that causes amenorrhea (missing periods), extreme weight gain or loss, and being underweight, overweight, or obese can make it hard to get pregnant.

Obesity may disrupt sex hormones, causing infertility, according to experts. In women, fat cells convert androstenedione into estrone, which influences the complicated metabolism that regulates ovarian and testicular function.

“This can negatively impact the menstrual cycle and make ovulation less regular,” says Caroline Apovian, M.D., co-director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital in Boston and a Harvard Medical School professor.

She adds that obesity can lower testosterone and cause hypogonadism in men. Obesity decreases semen quality, sexual dysfunction, and endocrine function. Obesity-related high body temperatures, especially around the scrotum, can harm sperm.

Body fat distribution may also affect fertility. The Journal of Clinical Endocrinology & Metabolism reported that women with higher waist circumferences and more abdominal fat were less likely to ovulate than those with identical BMIs but lower waist circumferences.

Obesity Affects Fertility Treatments

Obesity can also make fertility treatments harder to succeed. In one Journal of Reproductive Science study, women with a higher BMI and belly obesity were less likely to get pregnant with assisted reproductive technologies, including hormone-stimulating drugs like clomiphene citrate.

In a Fertility and Sterility research, overweight and obese women who used gonadotropins to induce egg development needed larger doses and generated fewer follicles.

Obesity can also make it harder to get pregnant with more expensive and intrusive IVF treatments. Another Fertility and Sterility study indicated that higher BMIs reduced IVF success rates. Dr. Apovian believes it complicates things.

“With IVF, you are pumping women full of hormones to get as many eggs to fertilize, and if you already have a woman with an abnormal hormone milieu due to obesity, they may have to do more and more cycles—and that is not without complications and huge costs.” Obese patients may be advised to delay IVF until they lose a specified amount of weight, depending on their biological clock.

Obesity may harm the pregnancy. Obese women were 1.3 times more likely to miscarry, according to a meta-analysis, while BMC Medicine showed that obese IVF patients were more likely to miscarry early. According to the American College of Obstetrics and Gynecology, obesity increases the risk of gestational hypertension, preeclampsia, gestational diabetes, and obstructive sleep apnea during pregnancy.

Above Weight

One of the biggest factors affecting fertility is your birth year, not your weight. Dr. Boots says age affects fertility. According to the CDC, 22% of women 30–39 who are attempting to conceive have trouble, compared to 13% of those under 30. Older women have fewer eggs and more defective chromosomes, making pregnancy less likely. Older women often have greater health issues that can affect fertility. Age increases miscarriage risk.

Polycystic ovarian syndrome (PCOS), which affects one in 10 women of reproductive age, can cause obesity and fertility difficulties. PCOS causes intermittent ovulation and increased male hormone production, making pregnancy harder. PCOS causes irregular cycles and weight gain. Dr. Boots warns that BMI is not the only reproductive factor in PCOS patients. She observes that insulin resistance may affect ovulation and conceiving in women with PCOS.

Combating Obesity

Obesity control helps couples planning a family. Although it’s hard to lose weight with diet and exercise alone, making some modest lifestyle changes—reducing processed foods, moving more—will improve health and prevent pregnancy issues.

Obese women may be more likely to get pregnant if they lose 5–10% of their weight. Dr. Boots believes weight loss can boost unaided conception. In 2022, PLOS Medicine found that women who exercised without dieting or lowering their BMI were more likely to conceive.

If lifestyle modifications don’t work, try medicines or bariatric surgery. The latest generation of weight loss medications like Wegovy have shown an average of 15% body weight loss, but they are not recommended for pregnant women due to a lack of data on their safety. Dr. Boots advises stopping drugs two months before conceiving.

Bariatric surgery too. Dr. Apovian says bariatric surgery is the best approach to shed 100 pounds in a year. This doesn’t make you fertile: Since nutritional insufficiency is frequent after bariatric surgery, doctors recommend waiting at least a year before having children. “That can be dangerous for both mother and fetus,” she says.

If you are concerned about your age and pregnancy, you can conduct an egg retrieval and then focus on modifications that may minimize obesity and increase fertility treatment success. Weight loss before pregnancy may reduce pregnancy difficulties. Dr. Apovian suggests taking a year to optimize your lifestyle, whether it’s drugs, surgery, or something else.

Dr. Boots advises obese infertiles to be gentle to themselves and take care of their emotional health. “Infertility is stigmatized. Self-blame is already present. Weight makes it even more delicate.”

Talk to your doctor about the best method for you and what other counseling and support is available on your pregnancy journey. You’re not alone. Many obese people have become pregnant, and more firms are offering fertility treatment to their staff.

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