Being Overweight Reduces Chances of Pregnancy

Obesity and Infertility

Did you know that half of all women of reproductive age are overweight or obese? 

And while we often hear about obesity increasing the chance of high blood pressure, high cholesterol, diabetes, breathing problems, arthritis and cancer, it also affects fertility in both men and women. Being overweight or obese can result in lower conception and higher pregnancy complication rates. 

BMI rankings

A person is defined as being overweight or obese based on their Body Mass Index (BMI). Overweight individuals have a BMI range of 25-29.9 kg/m², while those who are obese have a BMI greater than 30 kg/m². You can check your BMI by visiting your health care provider or entering your height and weight into an online BMI calculator.

Obesity affects fertility

Being overweight can hinder a woman’s ability to achieve pregnancy. There is a higher rate of menstrual abnormalities in women who are overweight and obese. Obese women have a 15 percent lower chance of pregnancy in the first year after stopping contraception. Women with BMIs greater than 27 kg/m2 have three times the risk of anovulation (not making an egg every month) compared to their thinner counterparts. 

Obesity also affects pregnancy chances when it comes to fertility treatments. Increased BMI is associated with decreased responsiveness to both oral and injectable fertility medications and a 10 percent lower pregnancy rate with IVF. A higher BMI can also mean poorer egg quality and uterine lining, leading to increased miscarriage rates. 

Risks during pregnancy

When overweight and obese women conceive, they and their babies face a number of increased risks. 

For mom:

• Pregnancy-related diabetes
• High blood pressure
• Preeclampsia
• Preterm delivery
• Stillbirth
• Cesarean section
• Shoulder dystocia

For baby:

• Distress during labor
• Early neonatal death
• Neural tube defects (i.e. spina bifida)
• Heart anomalies
• Cleft lip and palate
• Hydrocephaly 
• Limb abnormalities

These infants are more likely to be obese as adults, perpetuating the cycle of obesity.

Overweight men face risks, too

The negative impact of being overweight or obese is not limited to women. Obese men can have lower sperm concentrations and motility as well as erectile dysfunction, making intercourse difficult. These changes are caused by higher estrogen levels, lower testosterone levels, and increased scrotal/testicular temperatures.

Weight management is key

For all these reasons, couples hoping to conceive should focus on a weight management program that is based on changing their lifestyle. 

Cutting calories is the cornerstone of weight loss. How much you eat (i.e. your total daily caloric intake) is more important than what you eat. Decreasing your daily caloric intake by 500-1000 calories a day from what you were eating, should result in you losing one or two pounds a week – which can add up to a 10 percent loss over six months. Any successful lifestyle change should also include physical activity. 

Other weight loss options

If just changing your lifestyle doesn’t help you lose weight, you may want to discuss diet medications or even bariatric surgery with your doctor. Bariatric surgery in women can normalize menstrual cycles, correct ovulation and improve sexual function and pregnancy rates. 

After weight loss surgery, there can be pregnancy-related complications, but these are rare and for some patients the benefits of surgery will outweigh the risks. 

Unfortunately all of these interventions take time. You will want to look at all the benefits of losing weight and balance them against the decline in fertility that inevitably comes with age.

For more information about how weight may affect your fertility, talk with the Reproductive Health Specialists at Methodist Women's Hospital.