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Obesity and Infertility

By Dr Ananya Mandal, MD

Obesity is a rising epidemic affecting millions worldwide. Obesity also significantly affects a woman’s capacity to carry on a term pregnancy.

Obesity is defined by an extraordinarily high Body Mass Index (BMI) in which the index is a reflection of body fat content. Around 1 in 4 women are at least overweight as per surveys and studies. The rates are higher among women facing problems of conception.

Along with several other sexual health problems caused by obesity, infertility is an important one leading to the disturbing trend of need for and failure of assisted reproductive techniques for conception.

Obesity and infertility

One of the best established connections between obesity and reproductive problems is the link between obesity and infertility. Obesity decreases the rates of successful pregnancy in natural conception cycles.

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 as well.

High levels of leptin and low levels of adiponectin may also reduce rates of conception. Fertility can be partially restored if weight loss can be achieved.

Obesity and anovulation

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.

Studies show that women having anovulation related infertility is 30% higher in women with BMI ranged between 24 and 31 as compared to that of normal weight women. Furthermore for those with BMI over 31, the chance is even 170% higher.

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

Studies show that in obese women with anovulation, the underlying cause is most likely due to polycystic ovary syndrome (PCOS). 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.

Obesity and complicated 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.

Obesity and miscarriage

Obesity raises the rate of miscarriage and thus decreases successful pregnancy rates among obese women. This could be due to various causes including:-

  • Poor quality of eggs or ovum
  • Defective implantation or reception of the fertilized egg onto the womb mainly due to insulin resistance
  • Defective and altered levels of hormones that help in sustaining pregnancy

Obesity and assisted reproductive technique failure

Obesity is responsible for high failure rates of successful pregnancy even after employing artificial methods including stimulation of ovulation and assisted conception.

The British Fertility Society recommends that, “Women who are obese must initiate a weight reduction programme and those severely overweight (defined as having a BMI of 36 or more) should not receive treatment until their weight has reduced.”

Obesity and hormones

Obesity leads to decrease in testosterone, follicle stimulating hormone, inhibin B and sex hormone binding globulin. This leads to low sperm count and quality in obese men.

In obese women there is increase in androgen metabolism and elevated estrogen levels. Obese men show low estrogen and low testosterone levels as well.

Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: Apr 8, 2013

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