Obesity, defined by the World Health Organization as having a Body Mass Index of 30 kg/m2 or greater, is a risk factor for infertility, as well as subfertility, or reduced fertility, in women. The reasons why obesity causes fertility problems in women are not well-understood, but some scientists speculate that obesity-related disturbances of certain metabolic hormones, including insulin and leptin, may harm a women's fertility. Weight loss and treatments to treat underlying health problems such as polycystic ovary syndrome may reverse obesity-related infertility.
The Link
Obese women have a higher risk of infertility compared to their lean counterparts. One study, published in "Human Reproduction" in 2007, concluded that among more than 3,000 subfertile women trying to get pregnant, women with BMIs of 29 kg/m2 or higher had reduced odds of conception. Women with BMIs of 35 kg/m2 were 26 percent less likely to become pregnant over the course of a year than women with normal BMIs, whereas severe obesity indicated by a BMI of 40 kg/m2 decreased pregnancy odds by 43 percent. Female obesity is also associated with poorer outcomes following fertility treatments, according to a study published in "Journal of Human Reproductive Sciences" in 2010.
Causes
The mechanisms by which female obesity contributes to infertility and fertility problems are not entirely understood. A study published in "Cell Metabolism" in 2010, in which scientists studied the effects of obesity on infertility in mice, concluded that obesity-related infertility may be related to chronically-high insulin levels causing hormonal disturbances that disrupt ovulation. In some cases, obesity is associated with polycystic ovary syndrome, PCOS, a condition which also causes ovulation to be disrupted, thus contributing to infertility. However, obesity is also linked to fertility problems in normally-ovulating women, as was the case with the subjects of the 2007 "Human Reproduction" study. According to the "Human Reproduction" study's researchers, the causes of infertility among obese, ovulatory women are not known, but the metabolic hormone leptin may play a key role.
Complications
Besides reducing your fertility, obesity can also increase your risk factors for having complications during pregnancy. According to a review published in "The Journal of Family Planning and Reproductive Health Care" in 2009, obesity during pregnancy increases risk of maternal morbidity, mortality and fetal anomalies. Specifically, obesity during pregnancy may increase risk of preeclampsia -- a potentially life-threatening condition for both mother and baby -- and the fetus' risk for neural tube defects, according to a paper published in "Annual Review of Nutrition" in 2006. Additionally, according to a study published in "Journal of Human Reproductive Sciences" in 2010, there is an increased risk of early pregnancy loss among obese women.
Treatments
Losing weight can help reverse fertility problems related to obesity. According to the abovementioned 2009 review published in "The Journal of Family Planning and Reproductive Health Care," the most cost-effective treatment for infertile women with obesity is weight loss with a hypo-caloric diet which lowers BMI to 30 kg/m2 or less. In pregnant women that are obese, replacing refined carbohydrates and saturated fat with complex carbohydrates and unsaturated fats during pregnancy may benefit pregnancy outcomes, according to the 2006 "Annual Review of Nutrition" paper on obesity and pregnancy complications. In cases where obesity-related infertility is caused by PCOS, both weight loss and treatment with medications, such as clomiphene citrate and metformin, may help treat infertility, according to PubMed.
References
- "The Journal of Family Planning and Reproductive Health Care"; Obesity and Female Fertility: A Primary Care Perspective; Wilkes, S et al.; July 2009
- "Human Reproduction"; Obesity Affects Spontaneous Pregnancy Chances in Subfertile, Ovulatory Women; Jan Willem van der Steeg et al.; December 2007
- "Cell Metabolism"; Rescue of Obesity-Induced Infertility in Female Mice Due To a Pituitary-Specific Knockout of the Insulin Receptor; Kathryn J. Brothers et al.; September 2010
- "Journal of Human Reproductive Sciences"; The Impact of Female Obesity on the Outcome of Fertility Treatment; Pandey, S et al.; May 2010
- "Annual Review of Nutrition"; Maternal Obesity, Metabolism and Pregnancy Outcomes; King, JC; 2006
Member Comments