Obesity and infertility

BMI Weight Status
18.5-24.9 Normal
25-29.9 Overweight
30 and Above Obese
40 and Above Morbidly Obese

What is BMI and how is it used?

It is a number calculated from a person’s weight and height. It is an indicator of body fat for most people. It is used to screen for weight problems in adults. 

Disease risks can be estimated using BMI and other tests, such as:

  • Talking with your care team about what you eat and drink.
  • Talking with your care team about how active you are.
  • Family history of disease.
  • Blood pressure measurements.
  • Blood sugar and cholesterol lab tests.

How does obesity impact getting pregnant?

Research shows that getting pregnant is easier with a normal body weight. This is a BMI between 20 and 25. There is a lower natural pregnancy rate and a lower response to fertility treatment when a person has a BMI above 25.  This gets worse as the BMI gets higher. 

One reason for lower fertility rates in people with a high BMI is a higher chance of anovulation. This means an egg is not released each month. Studies show a 5 to 10% weight loss can bring back ovulation and help fertility. 

Pregnancy rates are lower in a person with a high BMI, even with our most advanced treatments like in vitro fertilization (IVF). Egg retrieval and embryo transfer are harder to do when a person has a high BMI. Studies show a lower IVF pregnancy rate in people with obesity, even when procedures go well.

How does obesity impact a pregnancy?

People with obesity, and who are pregnant, are at higher risk of:

  • Getting blood clots
  • Having high blood pressure
  • Miscarriage
  • Stillbirth 
  • Having a premature baby
  • Having gestational diabetes
    • This can be hard to manage and can lead to larger babies.
    • It can lead to a difficult delivery and the need for a c-section.
    • It can also cause early blood sugar problems with the baby. 

People with obesity who have a c-section are more likely to have problems with healing. 

Studies show birth defects are more common in babies born from people with obesity.

How does obesity impact my partner?

Partners often have an influence on what we eat and drink and how we exercise. People who are overweight and obese are more likely to have lower sperm counts with lower motility (normal sperm movement). This lowers your chance of getting pregnant, even with fertility treatment. 

For all these reasons, your care team suggests you try weight loss before starting fertility treatment. It would be ideal if the weight loss effort was shared by your partner, especially if your partner’s BMI is also overweight or obese.

Obesity and Infertility Care Policy

If BMI is less than 30 (<30):

  • Start or keep doing treatment with standard preventive care measures.

If BMI is 30 to 39.9:

  • Start or keep doing treatment with standard preventive care measures.
  • Try to do safe weight loss with lifestyle changes.

If BMI is 40 to 49.9 and age is 35 years and older (≥35) or ovarian reserve testing is not normal:

  • Get screened for glucose, lipid, endometrial, and blood pressure abnormalities.
  • Keep doing treatment while trying to do safe weight loss.

If BMI is 40 to 49.9 and age is less than 35 years (<35) with normal ovarian reserve testing (or donor eggs are being used):

  • Get screened for glucose, lipid, endometrial, and blood pressure abnormalities.
  • Talk with your PCP or other doctor about bariatric surgery.
  • If your hemoglobin A1c is equal to or higher than 6.5 % (Hgb A1c ≥6.5%) or you have health problems that could be better with weight loss:
    • Try lifestyle changes and medical management for at least 6 months.
    • Talk with your doctor about bariatric surgery.
    • Get your HgbA1c below 6.5% before starting treatment.
  • If your hemoglobin A1c is less than 6.5% (Hgb A1c <6.5%) and you do not have health problems:
    • Try to do safe weight loss.
    • Keep doing treatment.

If BMI is greater than 50 (≥ 50):

  • Keep your infertility visit. Treatment will start when your BMI is below 50. 
  • Get screened for glucose, lipid, endometrial, and blood pressure abnormalities. Your IVF team and PCP will co-manage this. 
  • Make lifestyle changes. You may also think about bariatric surgery.

There is no policy for a partner's BMI. Your care team suggests partners share lifestyle changes. Work toward safe weight loss, especially men with obesity.

Last reviewed: 
December 2021

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