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Why Is BMI Important When Becoming a Surrogate?

January 31, 2024

Kristin Marsoli

For prospective surrogates, body mass index (BMI) requirements can be a source of frustration and confusion. If you are wondering, “Why is BMI so important when becoming a surrogate,” this blog post is for you!

Below, we answer some of the most common questions surrounding weight, BMI, and why it is still an important measurement when discussing pregnancy, surrogacy, and the health-related risks associated with being pregnant.

What Is BMI?

BMI is an estimate of a person’s body fat based on their height and weight. Because people who are overweight or obese are more likely to have weight-related comorbidities, including diabetes, high blood pressure, and polycystic ovary syndrome (PCOS), this calculation can help gauge your risk for having or developing these health conditions.

Learn more about assessing your weight and health risk and calculate your BMI on the National Heart, Lung, and Blood Institute’s website.

How Important Is BMI?

“I’m athletically built but have a high body mass index. My doctor confirms I’m healthy and says that BMI isn’t a true indicator of overall health. Is this true?”

Scientific studies abound on the validity of using BMI to measure overall health. While it is a useful metric, it does have some limitations. For example, it may overestimate body fat in athletes and others who have a more muscular build, and it may underestimate body fat in older persons and those who have lost muscle mass.

The calculation may also have an inherent height bias. However, when used along with the individual’s health and activity levels and other measurements such as waist circumference, BMI can be a useful screening metric in general.

We know from experience that certain fertility treatments work best with women who have a BMI between 18.5 and 24.9. If your BMI falls outside that range, don’t panic. Many surrogacy agencies will accept surrogate moms with body mass indexes up to 32 (so long as you are in good health and meet the other screening criteria).

Does BMI Affect Fertility and Pregnancy?

“My BMI is over 32, but I had no trouble getting pregnant myself. My babies were healthy with no complications.”

The process of getting pregnant naturally is very different than an IVF pregnancy. When becoming a gestational surrogate, a created embryo is implanted in the uterus, and fertility medications are used to aid in the implantation. The medications used in this process work best with women within a specific body mass index range.

Research published in the Journal of Assisted Reproduction and Genetics found that women with a higher BMI (classified as overweight or obese) tended to require “significantly higher” doses of gonadotropins and longer stimulation durations to become pregnant than their counterparts with a lower BMI. The extended time to conception means more time, money, and emotional expenditure for both the intended parents and the surrogate.

Why Does BMI Matter for Surrogacy?

“Even with a higher BMI, I can still get pregnant as a surrogate. Why does it matter?”

Although women with a higher BMI can still conceive and carry a healthy, successful pregnancy, higher levels of body fat have been linked to pregnancy-related complications, such as gestational diabetes and preeclampsia. These conditions can endanger the surrogate's health as well as the baby's health.

By keeping within a BMI of 32 or lower, surrogate moms are likely to respond better to treatments, get pregnant sooner, and have better health-related outcomes for themselves and the baby they are bringing into the world.

Still Have Questions? We’re Here To Help! and our remarkable surrogate community are here to guide and support you at every step of your journey. Find out if you qualify to be a surrogate in our related blog post. If you feel like you’re a good fit, we’d love to get to know you better! Complete our application to get started.

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