Weight + infertility

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When people think about how weight affects their health, they focus on diseases and disorders. Diabetes, heart disease, and thyroid dysfunction aren’t the only health concerns that can exist though. Physicians have found that body mass index (BMI) can have a profound effect on a person’s fertility. Both men and women can be affected by their BMI when trying to conceive, whether they are underweight or overweight. SGF physician, Nancy Durso, M.D., who sees patients at SGF’s Fredericksburg, Virginia, office, provides information and resources for patients concerned about how their BMI might affect their fertility.

What is body mass index?

Body mass index (BMI) is a number calculated from your weight and height that roughly correlates to the percentage of your total weight that comes from fat (as opposed to muscle, bone, or organs). The higher a person’s BMI, the higher the percentage of fat in his or her body. If your BMI is under 18.5, you might be underweight. Between 18.5 and 24.9, you are in the normal BMI range for your height. A BMI over 25 is considered overweight, and over 30 is considered obese.

Calculate your BMI

Does BMI affect fertility?

There are numerous potential complications for overweight women trying to get pregnant including:

  • Lower response to medication used to regulate or initiate ovulation.
  • Greater need for carefully titrated dosing of medication, especially in patients with polycystic ovaries (PCO).
  • Greater frequency of over-response and the risk of over-stimulation and/or multiple pregnancies in response to medications used to induce ovulation. And if a multiple pregnancy is conceived, there are greater obstetrical complications in patients with excessive BMI than in multiple pregnancies in patients with a normal BMI.
  • More complicated IVF cycles (besides those complications listed above) including
    • Fewer eggs retrieved
    • Greater technical difficulty retrieving eggs with greater risk of bleeding or injury
    • Greater difficulty with embryo transfer in visualizing the uterus and accomplishing the embryo transfer effectively
    • Lower embryo implantation rates
    • Lower IVF success rates
    • Higher miscarriage rates

At Shady Grove Fertility, patients must have a BMI of less than 40 before initiating an IVF or egg freezing cycle and a BMI less than 50 before initiating an ovulation induction, intrauterine insemination (IUI), or frozen embryo transfer cycle.

Maintaining a healthy weight 

There is a strong correlation between a woman’s BMI and her fertility potential. While not every woman who is underweight or overweight will have difficulty conceiving, there are many who do. For a woman’s reproductive system to function properly, a healthy amount of fat needs to be present. Women who are underweight lack the appropriate amount of fat needed for reproduction, causing their bodies to ovulate infrequently or not at all. Even the smallest weight gain can help restart the reproductive system. 

Overweight women can experience insulin resistance, which makes managing a healthy weight difficult. Unbalanced insulin levels may cause the ovaries to produce an excess amount of male hormones and stop releasing eggs, which makes conception challenging. It’s important not to forget about your partner. Overweight men have shown to have abnormal semen, which may attribute to low sperm count and low sperm motility (movement). 

Your SGF physician will discuss with you the importance of your weight as part of the overall review of your medical records and history. We will use this information and, when necessary, we will have a discussion on the serious impact of being underweight or overweight on your general health as well as your fertility care. SGF’s Wellness Center can provide nutritional services for patients who need to work toward their ideal weight for optimal fertility outcomes. 

Learn more about SGF’s Wellness Center

Medical contribution by Nancy Durso, M.D.

Nancy M. Durso, M.D., FACOG, is board certified in obstetrics and gynecology and reproductive endocrinology and infertility. She loves to help individuals and couples achieve their goal of pregnancy and parenthood. She currently sees SGF patients at the Fredericksburg, Virginia office.

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Editor’s Note: This article was originally published in September 2021 and has been updated for content accuracy and comprehensiveness as of December 2023.

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The Impact Of Weight On Fertility

Weight can often be a sensitive topic, but it’s important to address, not only because the rate of obesity is increasing but also because it can have a significant impact on your overall health and your ability to get pregnant—whether you’re undergoing fertility treatment or not.

What Is Considered A Healthy Weight?

A person can determine if he or she is maintaining a healthy weight by using a body mass index(BMI) score. BMI measures the percentage of body fat based on your height and weight. A normal (or “ideal”) BMI falls between 19 and 25.

How Does Weight Impact Female Fertility?

Studies that have compared overweight and obese women with women of normal weight who are using assisted reproductive technology (ART) treatments have shown excess weight having negative effects such as:

  • Lower pregnancy rates
  • Increased miscarriage rate
  • Lower rate of a live birth

In addition, because BMI is strongly connected to treatment success, obese women who are undergoing ART may:

  • Need higher and longer doses of ovarian stimulation medication
  • Have fewer or more immature eggs to retrieve or more cancelled cycles due to an inadequate response
  • Experience higher risk of bleeding, damage to surrounding organs, and an anesthesia-related complication during surgery or egg retrieval
Furthermore, a higher BMI can cause problems with pregnancy, such as:
  • Gestational diabetes
  • High blood pressure
  • Cesarean section (also known as a C section)
  • Pre-eclampsia
  • Birth defects

Women who are underweight may not be getting adequate nutrition or may have hypothalamic amenorrhea that keeps them from ovulating on a predictable basis as well. Studies have shown though that in patients whose infertility is specifically due to weight, correction of the underlying disorder can lead to pregnancy in up to 70 percent of women.

How Does Weight Impact Male Fertility?

Just like with women who have fertility complications related to BMI, men can experience similar difficulties. If men are overweight, it can affect sperm count and sperm motility (movement). When the male hormones are increased (a result of a higher BMI at a heavier weight), it can impair the man’s ability to make sperm on a regular basis. The natural balance of testosterone and estrogen can be affected, which then may affect the ability to produce sperm. Men who are obese can also experience warming of the scrotum. If the scrotal temperature increases by 1 or 2 percent, it can impact sperm production or survival.

Weight Loss Improves Health And Outcomes

The good news is, a modest weight loss of 5 to 10 percent can affect a woman’s ability to resume regular ovulation if her inability to conceive is associated with weight alone.

If men are able to achieve a healthier BMI, that, too, can greatly improve their sperm production. Men produce millions of new sperm every day, making it highly beneficial to men who want to alter their lifestyle habits. Sperm takes about 72 days to mature, which means that men who lose weight or make positive lifestyle changes only need to wait about 3 months before seeing improvements in sperm quality—and an increase in their chances of reproductive success.

Exercise And Fertility

Many patients ask how much exercise is ok when they’re trying to get pregnant. While the link between exercise and fertility is a difficult to define with certainty, some facts have been well established.

  1. Intense physical activity, such as that of competitive female athletes, can disturb the menstrual cycle, but moderate activity has little effect on the cycle.
  2. Obesity is associated with decreased fertility. Weight loss in obese women can improve their fertility. Weight loss can also improve menstrual regularity in obese women with polycystic ovary syndrome (PCOS).
Improve Your Chances Of Conception

At Shady Grove Fertility, we always recommend and encourage overweight and obese patients to move towards the normal weight range based on their height through healthy diet and exercise. We focus on structured weight loss programs that include behavioral modification, in addition to regular exercise with a minimum of 30 minutes of moderate activity at least 3 days per week (always check with your physician before beginning any type of exercise regimen).

Patients and physicians can work together to non-invasively help a woman or man reach an optimal weight for conception. Being aware of the importance of body weight on reproduction can enable couples to maintain their ideal body weight before they begin fertility treatment. When patients have their weight at the ideal level, it can greatly increase their chances of reproductive success and reduce potential risks and complications.

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