Weight and Fertility: A Review
May 2014
Volume 5, Issue 2

ASRM Recommendations for Counseling Patients on the Effects of Weight on Fertility

Fertil Steril. 2013;100(3):631-637

Fertil Steril. 2013;100(3):631-637.
Fertil Steril. 2008;90(5 Suppl):S21-29.
 

Two reports from the American Society for Reproductive Medicine (ASRM) offer practitioners guidance on the effects of weight on fertility.

In 2008, the ASRM released “Obesity and Reproduction: an Educational Bulletin” to provide an update on the effects of obesity on reproductive health and to offer suggested treatments for obesity. The following are highlights of the bulletin:

  • Obesity is associated with menstrual dysfunction, ovulatory dysfunction, decreased fertility, and increased risk of miscarriage, birth defects, and obstetric/neonatal complications.
  • Women who are obese and attempting to conceive should receive counseling on the potential medical, obstetric, and neonatal complications.
  • Obesity may negatively affect male fertility; while the exact cause of this association is not clear, obesity has been linked to abnormal semen parameters.
  • Diet and regular exercise are the first-line treatments for obesity; weight loss has been linked to return of ovulatory function and a reduced miscarriage rate in obese women who were previously infertile.1,2
  • Pharmacotherapy may be appropriate for women with BMI ≥30 kg/m2, or BMI ≥27 kg/m2 plus obesity-related risk factors or disease, who do not respond to a 6-month trial of lifestyle modification.
  • In women with polycystic ovary syndrome, metformin in combination with a low-calorie diet has been linked to weight loss, return of ovulation, and improved fecundity. 
  • Bariatric surgery, when indicated, improves obesity-related comorbidities including menstrual irregularity and infertility in women with a BMI ≥40 kg/m2; pregnancy is not recommended during the first year after bariatric surgery.

In 2013, the ASRM released “Optimizing Natural Fertility: a Committee Opinion” in which the society offers recommendations on how to counsel patients with no evidence of infertility on how to optimize the likelihood of becoming pregnant. In it, the ASRM reports that fertility rates are decreased in women who are underweight or obese, citing a 2004 study by Hassan and Killick in which the time to conception was increased more than twofold among overweight/obese women (BMI >25 kg/m2) and more than fourfold among underweight women (BMI <19 kg/m2).3 The ASRM notes that there is little data on the effects of normal variations in diet on fertility.

References
1. Clark AM, Thornley B, Tomlinson L, Galletley C, Norman RJ. Weight loss in obese infertile women results in improvement in reproductive outcome for all forms of fertility treatment. Hum Reprod. 1998;13(6):1502-1505.

2. Clark AM, Ledger W, Galletly C, et al. Weight loss results in significant improvement in pregnancy and ovulation rates in anovulatory obese women. Hum Reprod. 1995;10(10):2705-2712.

3. Hassan MA, Killick SR. Negative lifestyle is associated with a significant reduction in fecundity. Fertil Steril. 2004;81(2):384-392.

Commentary

Tamara L. Wexler, MD, PhD, is an endocrinologist specializing in reproductive and neuroendocrinology, and an Attending in Medicine, Massachusetts General Hospital, Boston, MA.

The ASRM 2008 education bulletin highlights the spectrum of findings regarding the association between weight and fertility. While the majority of studies at this point suggest that overweight/obesity negatively impact fertility, there have been studies that do not find a statistically significant relationship.1 In addition, the mechanism of action for the impact of overweight/obesity on fertility is not clear—while earlier studies may have postulated that the association was due to irregular menses or ovulatory function, other studies suggest that this is not the case. The 2008 ASRM bulletin notes that more recent attention has focused on the potential role of elevated insulin levels.

The more recent bulletin, focusing on fertility in general, includes citation of research implicating underweight as another potential contributor to infertility.

The 2008 ASRM paper cites a 2004 population-based study by Hedley and colleagues which showed the prevalence of obesity by racial/ethnic group, with rates of 31% among non-Hispanic white women, 38% among Hispanic women, and 49% among non-Hispanic black women in the United States (1999-2002). Current data suggest similar rates for obesity,2,3 highlighting the disparity among groups as well as the general problem of overweight/obesity in the U.S.

Of course, the impact of underweight and overweight on the health of any woman is of importance apart from pregnancy. While this EndoScan focuses on the impact of weight (underweight and overweight) on conceiving, it is important to note the potential impact of obesity on overall maternal and pregnancy health, and that factors other than weight influence fertility, and the ASRM educational bulletins provide an excellent resource for these topics.

References
1. Howe G, Westhoff C, Vessey M, Yeates D. Effects of age, cigarette smoking, and other factors on fertility: findings in a large prospective study. Br Med J (Clin Res Ed). 1985;290(6483):1697-1700.

2. Ogden CL, Carroll MD, Kit BK, Flegal KM. Prevalence of childhood and adult obesity in the United States, 2011-2012. JAMA. 2014;311(8):806-814.

3. Centers for Disease Control and Prevention. Adult Obesity Facts. March 28, 2014.http://www.cdc.gov/obesity/data/adult.html. Accessed May 5, 2014.

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