BMI & Fertility
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.
How Does BMI Affect Fertility?
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. These parameters are important because 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
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. We will encourage, or, as necessary, require a program of weight loss combining dietary modification as well as an exercise program prior to embarking on fertility therapy and conception.
Medical Contribution by Stephen J. Greenhouse, M.D., In Memoriam, 2018.