Obesity & Reproduction
By Natalie Burger, MD
Obesity is an increasing problem in the United States; women/men of a reproductive age are not excluded from this problem. It is estimated that approximately 31% of white women, 38% of Hispanic women, and 49% of black women in the U.S. are overweight or obese. Many people are aware of the problems that obesity can cause – but many are not aware of the reproductive consequences.
Infertility in obese women is often (but not always) caused by ovulation problems – ovulation may be occurring very infrequently or not at all. Thus, women may have increasingly irregular/erratic menstrual cycles or no menstrual cycles at all. However, there is some evidence that this is not the only way that fertility can be affected. Although it is not known for sure, some research suggests that elevated levels of insulin (the hormone that allows the body to use glucose effectively) in overweight/obese women may be another factor which reduces fertility.
Studies done on women who have undergone IVF have, in general, shown there to be an adverse effect of carrying extra weight on the success of treatment. These studies also indicate a higher risk of early pregnancy loss for overweight or obese women undergoing IVF.
What is known for sure is that obesity increases the risk of many complications of pregnancy: pre-eclampsia, gestational diabetes, and need for c-section. The risk increases with the BMI (body mass index). Also, obesity has been linked to an increased risk of birth defects. In addition, there are concerns about the impact that maternal obesity may have on the subsequent development and health of the child.
Some providers believe that women should achieve a BMI of <35-40 (ideally 19-25) before pregnancy to minimize risks. However, women who are older may have to balance the benefits of postponing pregnancy to achieve weight loss with the risk of further fertility decline over time.
Men are not immune to the impact of obesity on fertility. The greater the BMI, the higher are the chances of low sperm count and decreased motility (movement) of the sperm. Obese men often have higher than normal estrogen levels. As well, in obese men, the scrotum remains in closer contact with surrounding tissue, thus raising scrotal temperature. In addition, there is concern that genetic abnormalities that are associated with obesity can also cause infertility in men.
Long story short…there are many reasons (fertility included) to try to maintain a healthy weight. In contrast to many aspects of infertility that you may not have control over (e.g. decreased ovarian reserve or fallopian tube blockage), you CAN take charge of your general health. It is optimal to achieve a BMI of 19-25 prior to pregnancy; however, even small changes in the right direction can have a large impact. Don’t be discouraged by thinking that you have to achieve a large amount of weight loss all at once – every little bit helps.
If you are wondering what your BMI is, ask your nurse (who can calculate it from your height/weight). Or consider looking on the internet for a ‘BMI calculator’ which will give you the answer. If your number is not where you would like it, consider it a potential aspect of health/fertility that you can take charge of!
If your general health and potential pregnancy health are not strong enough motivators, realize that it takes longer for women who are overweight/obese to achieve pregnancy – and they may require higher doses of more expensive medications and treatments to get there. You may be able to significantly save on the costs of fertility treatment by getting your weight in a good range…
Certainly, lifestyle changes involving a diet/exercise program are the 1st-line treatment for obesity. If you have questions about where to start, consider asking your doctor (or PCP) for strategies. For those women (or men) with a BMI > 30 who are not achieving results with lifestyle changes alone, some medications may be helpful in enhancing weight loss. For women (or men) who have a BMI >40 (or over 35 with serious co-existing medical problems), weight loss surgery may be a better and more efficacious option.
Addressing weight issues is never easy. Many folks may have already tried weight loss in the past with mixed results. However, the potential benefits for reproductive health are significant. Now is the time to make changes for a healthier you and a healthier pregnancy!