Fertility and Weight Loss

Couples hoping to conceive often hold the misconception that body weight has nothing to do with getting pregnant. In reality, there is a clear association between weight and fertility and your doctor may encourage, or, as necessary, require a program of weight normalization combining dietary modification as well as exercise prior to embarking on conception.

Posted on | Anitha Nair, MD | Comments ()

Couples hoping to conceive often hold the misconception that body weight has nothing to do with getting pregnant. In reality, there is a clear association between weight and fertility and your doctor may encourage, or, as necessary, require a program of weight normalization combining dietary modification as well as exercise prior to embarking on conception.

Patients with weight abnormalities find it hard enough to see a physician about something as intimate as trying to get pregnant. Their worries about weight can compound the emotional discomfort. What most patients don’t know is that obesity is a very common problem and weight counseling is a routine part of most doctor visits. It is surprising to many patients what weights are medically considered overweight, obese and extremely obese. Obesity is defined by a measure calculated by the height and weight of the patient to give the body mass index or BMI. Normal BMI is defined by an index of less than 25; overweight patients are defined by a BMI 25 or greater; obesity is defined as a BMI of greater than 30.

Ideal body weight results in the best outcome for fertility therapy and for both mother and baby. For those with abnormal weight who do conceive, greater complications of pregnancy exist including:

  • Higher frequency of early pregnancy loss (miscarriage)
  • Greater anesthesia and surgical complications if any surgery required
  • Greater frequency of hypertension, gestational diabetes, pre-eclampsia, stillbirth and other complication of pregnancy (rates of stillbirth are twice as high in obese patients compared to normal weight patients)
  • An increased risk of requiring a caesarean section delivery. The caesarean section rate is almost 50% in obese women and the postoperative complications following C Section are significantly higher.
  • Higher infant birth weights correlate with a greater delivery complication rate for those delivering vaginally.

Both underweight and overweight women and men suffer from a higher incidence of infertility. Normal BMI optimizes fertility treatment success. Modifying your weight may be the simplest, most cost-effective first step in improving your chance to conceive. In many cases, this can mean no additional treatment is needed.


Overweight or underweight women may have hormonal disorders, which may cause them to ovulate infrequently or not at all.


Generally, underweight patients (BMI less than 19) can be encouraged to gain more weight, and this alone often increases their fertility significantly or makes hormonal therapy more successful.


On the other side of the spectrum, many studies have demonstrated a clear and consistent decrease in fertility with increasing female weight. Overweight women who undergo weight loss (even as little as 10% of total body weight) may ovulate without the need for fertility medications.

Severe obesity in men has been shown to alter fertility due to imbalances in hormone regulation tied to sperm production. A simple reduction in weight may improve semen parameters.


Our goal at Shady Grove Fertility Center is to provide you with the best and safest outcome possible. Just as serious medical conditions like diabetes, hypertension or cardiac disease require treatment before embarking on fertility therapies, so should abnormalities in weight. Your doctor will discuss with you the importance of your weight as part of the overall review of your medical records and history. We will use this information and have a discussion on the serious impact of being underweight or overweight on your general health as well as your fertility care. 


It is not uncommon that patients are counseled that their treatments must be held until they achieve a target weight. In many cases, these couples will conceive spontaneously during this period. The good news is that normalization of BMI is very effective in yielding significant improvements to success rates for conception and with the proper motivation and help most patients can achieve their goals of normalizing their weight.

Blog written by Anitha Nair, MD
Dr. Nair is specialty trained reproductive endocrinologist, also known as a fertility specialist working at Shady Grove Fertility...