IVF and BMI: Your Personal Chances of Conceiving

Like many things in life, moderation is best when it comes to fertility factors that impact IVF success. 

Women who fall far outside what’s considered the normal range in body mass index (BMI) — either very under- or overweight — are likely to have a reduced probability of pregnancy with IVF. Abnormal weight can disrupt hormonal function and timely ovulation, making it more difficult to become pregnant in natural cycles. 

Your BMI is calculated from your height and weight. If your BMI is between 25 and 29.9, you are considered overweight. A BMI of 30.0 or greater is considered obese. If you are extremely underweight with a BMI below 18.5, you may have insufficient energy reserves for pregnancy. However, these BMI standards were established by medical research on medical conditions (like heart disease, diabetes) unrelated to IVF. 

A woman’s fitness can impact her chances of a successful pregnancy with IVF. Multiple studies have shown that obesity, in particular, is a highly negative factor. Physicians may recommend weight loss before attempting IVF to increase the chances of a successful cycle, but BMI is only one health factor to consider, so consult your doctor before making the decision on your own to lose weight before treatment.

High BMI

Let’s first look at how a high BMI can decrease your chances of having a baby with IVF.

► High BMI has been associated with poorer egg and embryo quality, and there may be other effects at the molecular level that we do not yet fully understand.

► A high BMI can cause a decreased amount of hormone medications to be available to your body.

► A high BMI can cause a technical challenge during the egg retrieval process. When a woman is overweight, her ovaries are often pushed up high and away in the abdominal cavity, making it difficult to reach and recover all the mature eggs with the retrieval needle.

► Excess fatty tissue may result in poorer image quality on the ultrasound, making it difficult to recover every egg. Fewer eggs recovered per cycle mean fewer possible embryos for transfer, reducing the likelihood of pregnancy from IVF.

► If IVF is successful, the obstetrician is also concerned about complications during the pregnancy, as well as labor and delivery, because the mother’s pre-pregnancy weight is associated with weight gain during pregnancy and the baby’s birth weight. Larger babies are at risk for difficult birth and birth injuries.

Though research has shown that a high BMI can hurt your chances of IVF success, remember that research results from the general population cannot be directly applied to your specific chance of pregnancy with IVF. Your BMI must be considered as part of your whole clinical picture, including multiple fertility factors, such as your reproductive history, ovarian reserve, age, partner’s sperm count and cause of infertility. For perspective, some women with normal BMI may have other factors working against them. So, while having a high BMI does not help, it is the holistic picture that is important in figuring out your next steps.

Visit our map to find an IVF Provider offering the Univfy® PreIVF™ Report free of charge to learn your probability of success based on your comprehensive health profile.

Should a patient who is age 39 with a BMI of 30 (high) take three months to lose 10 pounds before taking her IVF treatment? She should first find out her chances of IVF success now. Any delay in IVF could hinder her chances of having a baby by the time she starts her first IVF cycle, due to age-related factors like a decline in her ovarian reserve.


At the opposite extreme, your chances of becoming pregnant can also be impacted by a very low BMI (under 19).

BMI measures your body’s available energy reserves for taking on physical and physiological challenges. You need sufficient body fat reserves to ovulate and support your pregnancy. In fact, if BMI is too low, your doctor may ask you to gain weight before conceiving, so that you build up some reserve to help you through the first trimester, which can be especially challenging if you experience nausea, vomiting and decreased appetite.

Other clinical conditions (chronic diseases, such as diabetes, heart disease, autoimmune diseases, or unhealthy lifestyle factors, such as smoking) can also affect a patient’s chances of success with IVF. 

To find out how your BMI and other health factors such as age, ovarian reserve and reproductive history affect your chances of success with IVF, consult an IVF provider working with Univfy. 

The Univfy® PreIVF™ Report is the only personalized report that takes your holistic health data as well as the outcome data of individual providers to give you an accurate prediction of your chances of IVF success per cycle, as well as your financial options to pay for treatment.

We are rooting for you to succeed with your IVF treatment. Be sure to join us on Facebook and follow us on Twitter @Univfy.

The contents of this blog are for informational purposes only. Content in this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Reliance on any information provided by Univfy, Univfy employees, or others appearing in this blog or on the Univfy website is solely at your own risk.

About the Author:

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Mylene Yao, M.D. | Co-Founder and CEO of Univfy

Dr. Mylene Yao is a board-certified OB/GYN with more than 20 years of experience in clinical and reproductive medicine research. Prior to founding Univfy, she was on the faculty at Stanford University, where she led NIH-funded fertility and embryo genetics research and developed The Univfy Platform with the academic founding team. See her full bio here.

Heather Holland