Obesity & Infertility

How does Obesity affect Fertility 

Obesity is when a person’s BMI is more than 30. It is not just a cosmetic concern but a complex disease which involves an excessive amount of body fat. It is a medical problem that increases the risk of other diseases and health issues related to heart, diabetes, high blood pressure including several other sexual health problems. Among this infertility is an important one, and it could also contribute to failure of assisted reproductive techniques for conception.

A BMI between 19 and 24 is considered normal; less than 19 is considered underweight. A BMI between 25 and 29 is considered overweight and greater than 30 places you in the category of obese.

Women at less than normal BMI should work with their doctor to understand the cause of this situation, and develop strategies to correct it. A BMI in the obese leads to irregular menstrual cycles and anovulation.

How are they connected?

Obesity decreases the rates of successful pregnancy in natural conception cycles also. Many underweight, overweight, and obese women have no problem getting pregnant. But others will have problems conceiving, most often due to ovulation problems (failure to release eggs from the ovaries).

In women who are undergoing reproductive therapies by accelerating and augmenting their ovulation cycles for better chances of conception, obesity may reduce the rates of pregnancy. High levels of leptin and low levels of adiponectin seen in blood of obese women could be the reason behind this. Fertility can be partially restored if weight loss can be achieved.

How is an-ovulation linked to obesity?

Studies show that women having anovulation related infertility is 30% higher in women with BMI ranging between 24 and 31 as compared to that of normal weight women. Furthermore for those with BMI over 31, the chance is even higher. Obesity is likely to cause insulin resistance that is linked to anovulation or failure of a woman to produce the egg from each ovary each month. Insulin levels and obesity also lead to altered sex hormones, high androgens (male hormones), high levels of free growth factor 1 etc. 

Only 5% loss of body weight can increase ovulation rates and reduce biochemical abnormalities.

Polycystic ovarian syndrome or more popularly known PCOS is associated with obesity or overweight along with symptoms of high male hormone secretion such as hairiness, acne, high cholesterol level and insulin resistance . It is a very common condition in young women (about 8%–10%). Not all women with PCOS are overweight or obese, but many women with PCOS have signs of insulin resistance and/or obesity. A low-calorie diet and exercise may lead to weight loss, regular menstrual cycles, and ovulation.

How can Obesity complicate pregnancies ?

Obesity leads to common pregnancy complications like pregnancy induced high blood pressure called preeclampsia or in severe cases eclampsia. Obesity and related insulin resistance is also responsible for diabetes during pregnancy or gestational diabetes. It is responsible for high failure rates of successful pregnancy even after employing artificial methods including ovulation induction and assisted conception.

Obesity decreases successful pregnancy rates among obese women and raises the rate of miscarriage. Some of the common causes are –

• Poor quality of eggs or ovum
• Insulin resistance can cause defective implantation or reception of the fertilized egg onto the womb. 
• It also causes defective and altered levels of hormones that help in sustaining pregnancy
• In obese women there is an increase in androgen metabolism and elevated estrogen levels. 

Does obesity affect men’s chances too?

Obesity in men may be associated with changes in testosterone levels and other hormones important for reproduction. It also leads to decrease in testosterone, follicle stimulating hormone, inhibin B and sex hormone binding globulin. This leads to low sperm count, low sperm motility (movement) and low sperm quality in obese men. 

Conclusion

Supportive research and evidence over the years has highlighted that obesity lowers the success rates of in vitro fertilization (IVF), lower pregnancy rates and higher miscarriage rates in obese women. Women are at an increased risk for developing pregnancy-induced (gestational) diabetes and high blood pressure (pre-eclampsia). They also have a higher chance of delivering by cesarean section. Children of obese mothers are at increased risk of some birth defects and having diabetes in future. 

However, even obese women with normal ovulation cycles have lower pregnancy rates than normal weight women, so ovulation isn’t the only issue. Consulting your doctor before becoming pregnant can help identify other disorders related to obesity that impact pregnancy such as thyroid disease, insulin resistance, and diabetes, which will help you guide and monitor to take the next step forward more smoothly.