You might be wondering why you can’t get pregnant. You just had IVF, but you are not pregnant. You don’t want to admit it but you may be a little overweight. There is evidence that obesity lowers the success rates of in vitro fertilization. In addition, some studies show a higher rate of spontaneous miscarriage. For obese woman, there is an increasing amount of evidence that many complications of pregnancy for both the mother and baby increase. For the mother, there can be gestational diabetes and preeclampsia. For the baby, birth defects are increased.

There are also infertility issues for men that are obese. Obesity has been linked to changes in testosterone levels. Low sperm count and low sperm motility occur more often in obese men. So it would be best for both partners to be at optimal weights to get pregnant. But what is the optimal weight and how is that determined?

One of the easiest ways to determine your optimal weight for fertility is to check your body mass index or BMI. To calculate your BMI, you divide your weight in kilograms with your height in centimeters or use a BMI table. The table converts your height and weight into kilograms and meters. Your BMI score is then displayed as kg/m2. One of the best BMI tables is put out by the National Heart, Lung and Blood Institute and is located at https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmi_tbl.htm. You can also use this BMI chart: http://www.bmi-chart.info/bmi-chart

A normal or ideal BMI is between 19 and 24. Less than 19 is considered underweight. A BMI between 25 and 29 is considered overweight. And anything higher than 30 places you in the obese category.

Your BMI affects your fertility whether you are overweight or underweight.  An underweight BMI of less than 18.5 causes irregular periods and may cause ovulation to stop. A BMI of 17.5 or less may indicate an eating disorder. You should consult your doctor if you have a low BMI.

A high BMI in the obesity range may lead to irregular periods and irregular ovulation. You should consult your doctor for an evaluation of hormonal levels related to ovulation. A preconception visit can also identify other obesity related disorders that impact pregnancy. Those disorders include thyroid disease, insulin resistance or Type 2 diabetes. Even if the obese woman has normal ovulation, it may still be difficult to get pregnant and bring a baby to full term.  Obesity lowers the success rate of IVF. In addition, there is a relatively common disorder called polycystic ovarian syndrome (PCOS) which many obese women have. PCOS decreases fertility and may lower the success rate of IVF as well.

Changing your diet and following a fertility diet may help you lose weight. If you have a normal BMI, you will increase your chances of getting pregnant and having a healthy baby. You should always consult your doctor first before dieting and exercising. For more information on reproductive health visit http://www.reproductivefacts.org/ You can find more information on the fertility diet on our blog post what should I eat to get pregnant.

Reprinted with permission from American Society for Reproductive Medicine