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How BMI Affects Fertility and IVF Success

Authored and medically reviewed by Dr. Eli Reshef

Dr. Eli Reshef is a reproductive endocrinologist and fertility specialist who sees patients in Chicago and the greater Chicagoland area.

When trying to conceive—whether naturally or through fertility treatment such as in vitro fertilization (IVF)—body weight can play a significant role in fertility outcomes. At Advanced Fertility Center of Chicago (AFCC), we understand that weight is a sensitive issue, but we also know that providing evidence-based information can empower patients to take control of their general and reproductive health.

Let’s explore how Body Mass Index (BMI) affects ovulation, pregnancy success rates, and the safety of fertility treatments like IVF.

What is BMI?

Body Mass Index (BMI) is a measurement that estimates body fat based on height and weight. It is commonly used in medicine to assess whether someone falls into a healthy weight range.

Here’s how adult BMI categories are defined by the CDC:

• Underweight: BMI below 18.5

• Normal weight: BMI 18.5 – 24.9 

• Overweight: BMI 25 – 29.9 

• Obese: BMI 30 - 39.9 

• Severely obese: BMI 40 or higher

Calculating BMI: There are numerous tools on the Internet that allow BMI calculation by simply inputting height and weight. Enter “BMI” to any search engine.

How BMI Affects Fertility

1. Ovulation and Natural Conception

Weight impacts hormonal balance and ovulation regularity. Women at both extremes—underweight and obese—may experience irregular ovulation or even anovulation (lack of ovulation), making conception more difficult.

Weight loss of even 5-10% in overweight individuals can help restore ovulatory cycles and improve natural fertility.

2. IVF Success Rates and BMI

Studies (such as this one from the National Institutes of Health), including data from our own clinic, consistently show that higher BMI is linked to lower IVF success rates.

Key findings:

• Women with a BMI over 30 have lower pregnancy rates compared to those with a normal BMI.

• Obesity is associated with poorer egg quality, lower embryo implantation rates, and higher miscarriage risks.

• Women with BMI under 30 had significantly higher IVF success rates in our clinic’s data review.

3. BMI and the Safety of IVF Procedures

Higher BMI can also impact the egg retrieval process in IVF.

Challenges of high BMI during egg retrieval include:

• Ovarian positioning: Excess abdominal fat pushes the ovaries higher in the pelvis, making them harder to reach safely with a retrieval needle.

• Ultrasound visibility: The extra tissue can create blurry ultrasound images, making it difficult for a physician to precisely locate and retrieve eggs.

• Procedure risks: Obesity is linked to higher risks of complications from anesthesia and during recovery.

4. BMI and Pregnancy Complications:

A higher BMI can increase miscarriages, premature deliveries, underweight or overweight babies, difficult deliveries, C-section rates, birth injuries during vaginal deliveries, diabetes and high blood pressure during pregnancy.

What Can You Do?

If you’re struggling with fertility and have a BMI over 30, weight management strategies may increase your chances of conception—both naturally and through IVF.

Consider these steps:

• Work with a doctor or nutritionist to set realistic weight-loss goals.

• Focus on balanced nutrition and regular exercise rather than extreme dieting.

• Even a small weight reduction (5-10% of body weight) can improve ovulation and pregnancy rates.

• Medications (e.g., GLP1-RAs) or weight-reduction surgery may be appropriate for some patients.

Final Thoughts

At AFCC, we are committed to providing compassionate, personalized care to all individuals. If your weight may be affecting your fertility, we’re here to guide you through options that can help optimize your chances of success.

Have questions? Contact us today to schedule a consultation with our fertility experts.

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