ARC® Fertility Blog

Weight affects fertility

Yes, Weight Matters to Your Fertility and Infertility Treatment

Medical conditions are often covered on tv shows and in movies; given their often large audiences, it’s especially important to get the facts right. A recent episode of the popular tv show “This is Us” recently tackled the topic of whether being overweight or obese negatively affects a woman’s fertility.

The storyline follows a character named “Kate Pearson” who is 38, obese and last season experienced a miscarriage. On this year’s premiere, a fertility specialist told Kate “At your weight, the chances for a successful pregnancy are very slim—even with IVF.” Obesity does affect pregnancy rates, increases the risk of miscarriage and may result in poorer outcomes with in vitro fertilization (IVF).

Despite the accuracy portrayed, many women reacted to the show with comments on social media noting they’d been able to get pregnant and deliver a baby despite their weight. Worth noting, the character on “This is Us” is also considered an advanced maternal age at 38 and has polycystic ovarian syndrome (PCOS) both of which have a major impact on the ability to get pregnant and delivery a healthy baby.

In real life, many underweight, overweight and obese women have no problem getting pregnant. But others – both obese and under-weight – will have problems conceiving, often due to problems with irregular periods and ovulation problems such as failure to release eggs from the ovaries. Other weight-related problems affecting the metabolic and endocrine systems may also lead to infertility.

So, while having to discuss your weight may be uncomfortable, weight loss – unlike other factors that affect infertility – is one area where it is possible to achieve change and a real increase in your chances of a successful pregnancy.

To determine if your weight might be an issue, you can find out whether your weight is considered normal, overweight, obese or underweight by calculating your BMI. There are many online tools that will tell you your BMI based on height, weight, waist measurement, sex and age. A BMI between 19 and 24 is considered normal; a BMI between 25 and 29 is considered overweight; a BMI over 30 defines you as obese; and a BMI below 19 is considered underweight.

A BMI in the obese range may lead to irregular menstrual cycles and ovulation problems. The additional fat increases estrogen which can interfere with ovulation. However, even obese women with normal ovulation cycles have lower pregnancy rates than normal weight women, so ovulation isn’t the only issue. It may be related to other disorders affected by weight that impact the ability to get pregnant including thyroid disease, insulin resistance and diabetes.

Also, polycystic ovarian syndrome which affects 8-10% of young women is present in 30-75% of women with obesity. Among other things PCOS may cause irregular menstrual cycles and increases hormonal and metabolic problems that affect fertility. A visit to a healthcare professional before becoming pregnant can help identify whether you have any of these conditions.

Having an overweight or obese partner may also affect your ability to get pregnant. Certain hormones, including testosterone, that are essential to reproduction may be affected by obesity. Low sperm counts and poor sperm motility (movement) are also more often associated with men who are overweight or obese than men who are a normal weight.

There is evidence that obesity may lower the success rates of IVF. Specifically, higher doses of gonadotrophins (hormones given by injection to stimulate the ovaries to produce eggs) are required, the response to ovarian stimulation may be poor, and fewer eggs are usually harvested. Further, fertilization rates are lower, the quality of embryos is lower and there are higher miscarriage rates.

Still, there are caveats about how much obesity affects IVF success, especially compared to other factors such as age. A review of research shows that most authors think there is an increased risk of miscarriage for overweight and obese women who become pregnant without medical treatment. However, “any further increase in risk after IVF or ICSI is debatable.” In fact, a recent study showed the impact of BMI on IVF success was strongly influenced by age. For women aged 36 or older, the effect of BMI is less influential than age.

One expert, Nathaniel DeNicola, M.D., an assistant professor of obstetrics and gynecology at George Washington University goes further, stating “there’s actually no definitive answer to whether or not body weight is a factor with IVF. There’s no question obesity decreases the chance of getting pregnant, but for IVF, body weight as a factor is unclear.”

There is some good news for any woman who is overweight or obese and trying without success to get pregnant. Data shows a weight loss as small as 5%-10% can improve pregnancy outcomes. Losing as little as 5% of body weight can result in a regular menstrual cycle, increase the frequency of ovulation and improve endocrine systems such as lowering fasting insulin levels. Whether you should try and lose weight – and how much– before pursuing infertility treatment may be different for older women who must also consider how waiting and being older may affect the likelihood of getting pregnant and delivering a healthy baby.

In “This is Us” when Kate and her husband meet with a fertility specialist, the doctor declines to take her on as a patient for IVF because her obesity will make pregnancy unlikely. In Dr. DeNicola’s opinion, this is “not entirely realistic” and he says informed patient consent is standard. However, some infertility clinics may have a BMI cutoff for IVF orintrauterine insemination (IUI) treatment.

A doctor who knows your unique situation including health status and medical history should lay all the issues out for discussion and informed decision-making. This may include their help with a healthy weight loss program to lower your BMI before starting treatment, if age is not an issue. While losing weight may be daunting, so is being a parent! And, finally, Kate’s doctor later changed her mind about starting IVF treatment. Always consult your own doctor and stay tuned…