Among the things that a woman can do to optimize her chances of getting pregnant – either naturally or with help – is to maintain a healthy body weight. Women who are either underweight or overweight have a lower fertility rate than normal weight women.
The United States is currently experiencing an obesity epidemic – over 60% of women are overweight and 33% are obese. A patient with a body mass index (BMI) over 25 is considered overweight; a patient with a BMI over 30 is considered obese. The association between a higher BMI and subfertility appears to be related to a hormonal imbalance of the insulin hormone. Having a higher insulin level can cause elevations in the male hormones, disrupting the normal ovulation process. However, even women who ovulate regularly and who have a higher BMI seem to experience a lower fertility rate.
Conversely, having a low BMI (I.e. <18.5) is also associated with a lower fertility rate. Though it is clear that underweight women who do not experience ovulation (and thus have irregular/absent periods) are at risk for infertility, even women who do experience more regular menstrual cycles may still have problems.
It is important to be honest with yourself regarding your weight. A BMI calculator can be easily found on the internet and can help you to assess your current weight status. An optimal BMI for fertility (and health) appears to be between 18.5 and 25. If you do not fall within this range, consider talking further with your physician about strategies to safely change your weight. Even if you are not able to modify your weight to this range, even small changes in the right direction can make a major impact on your health and fertility!