Rebel Wilson says she lost weight to improve her chances of having a baby. What experts say about the impact of BMI on fertility.

·4 min read

When actress Rebel Wilson announced to fans last November that she'd reached her goal weight after making 2020 her "Year of Health," she clarified that her diet and fitness journey was "not about a weight number, it’s about being healthy." What the Australian comic actress hasn't revealed until recently is that her transformation was prompted by her desire to have children.

As Good Morning America has reported, the 41-year-old opened up during an Instagram Live in late July about her doctor advising her to lose weight in order to improve her chances of getting pregnant. 

"It first started when I was going through, looking into fertility stuff and the doctor was like, 'Well, you'd have a much better chance if you were healthier,'" she shared. 

"I was actually a bit offended because I thought — even though I was bigger — I thought I was pretty healthy," the Pitch Perfect star added. "That's, kind of, what started it, that if I lost some excess weight, that it would give me a better chance for freezing eggs and having the eggs be a better quality."

Though Wilson has, presumably, yet to conceive — in May she posted on Instagram about receiving "bad news" and offered support to "all the women out there struggling with fertility" — her remarks raise the question of just how important weight is to the process. 

According to women's health expert Dr. Sherry Ross, being overweight can disrupt a woman's ovulation cycle, which in turn "can make it a challenge to conceive." Wilson has previously spoken about being diagnosed with polycystic ovarian syndrome (PCOS), which caused her to "[gain] weight rapidly." PCOS can also give rise to fertility issues, as it can cause women to not ovulate or to miss periods. 

Ross, the author of She-ology and co-founder of URJA Intimates skin care, tells Yahoo Life that having a body mass index (BMI) in the obese range — 30 or greater — "increases the risk of infertility due to ovulation problems."

Dr. Brian Levine of the reproductive health clinic CCRM New York supports this, citing findings from the American Society for Reproductive Medicine (ASRM) that "overweight women in the general population have a higher incidence of menstrual irregularity and a lower chance of conception within one year of stopping contraception compared with normal-weight women."

Having a low BMI comes with its own set of concerns, as Ross and Levine note that that too can interfere with regular ovulation. Levine points to a 2014 study which found the time to conceive increased fourfold for women with a BMI of less than 19 compared to those with a BMI between 19 and 24; for women with a BMI over 25, that time increased twofold. 

"Taken together, weight has an incredible impact on cycle regularity and reproductive outcomes," he tells Yahoo Life.

Of course, women of all shapes and sizes give birth every day, and conceiving is not an impossibility. But Levine says that being overweight increases a woman's risk of hypertension, dyslipidemia, diabetes, cardiovascular disease, sleep apnea, respiratory problems, osteoarthritis, and cancer, which make pregnancy high-risk. During pregnancy, there's also an increased risk of complications such as gestational diabetes, high blood pressure and pre-eclampsia, which could result in a "medically indicated preterm birth."

"Furthermore, obesity and extreme underweight are both associated with a greater risk of stillbirth," he adds. 

And just as excessive weight can bring on pregnancy complications, being underweight or not gaining enough weight during the pregnancy can result in preterm labor and a low-birth-weight baby, says Ross. 

The healthiest approach, she says, is to follow Wilson's lead by allowing oneself time to get weight and lifestyle habits under control. 

"It’s best to plan at least six to nine months ahead of actually getting pregnant so you can be your healthiest self before carrying your most vulnerable passenger," Ross says. "Women have to start eating a colorful and healthy diet, exercising regularly and maintaining a healthy BMI long before a planned pregnancy if they want to reduce pregnancy-related complications due to obesity and excessive weight gain during pregnancy. Working with a knowledgeable doctor and nutritionist who can support you and the baby will ensure a healthy outcome for both of you."

She acknowledges that women can often feel body-shamed, especially in a medical setting, and suggests that anyone wishing to conceive seeks out an ob-gyn with whom they can have a more supportive and empowering relationship. 

"The good news is there are plenty of obstetricians out there who will partner with you in a positive and healthy way," says Ross. "Feeling comfortable and being able to discuss concerns, fears and insecurities with the health care provider has to be first and foremost for the most important journey of a woman’s lifetime."

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