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BMI and Your Fertility

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.

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 in vitro fertilization (IVF) cycle and a BMI less than 44 before initiating intrauterine insemination (IUI) cycles.

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.

Editor’s Note: This article was originally published in September 2021 and has been updated for content accuracy and comprehensiveness as of July 2022.