Obesity Awareness Month
Obesity and Female Reproductive Function: A Review
By: Adair McCabe, DO
Director’s Note: Optimizing health and fertility is a multifaceted challenge. During Obesity Awareness Month, we examine the evidence for common effects of obesity on female reproductive function. Former FACTS elective student and family medicine resident, Dr. Adair McCabe, summarized a review article titled, “The impact of obesity on female reproductive function.” [4] In it, Metwally et al detail the relationship between obesity and problems with fertility as well as various reproductive disorders. Their article also discusses treatment interventions to improve fertility.
Introduction
This article [4] by Metwally et al discusses research on the effects of obesity on female reproduction and effective management strategies available at the time of publication (2007). Obesity remains a growing public health concern that is associated with multiple negative health outcomes, including an increased risk of infertility. The World Health Organization estimates obesity has nearly tripled since 1975. [1] In the United States, an estimated 41.9% of women are considered obese, with a body mass index (BMI) ≥ 30. [2][3]
“Obesity remains a growing public health concern that is associated with multiple negative health outcomes, including an increased risk of infertility.”
Obesity and Reproductive Disorders
Obesity is known to influence gonadal function, but the exact mechanisms and extent are still being investigated. Adipose tissue secretes adipokines such as leptin, adiponectin, ghrelin, and resistin; these molecules affect the body in different ways. [3] As of the time of publication, leptin was the most studied, and research shows leptin has an inhibitory effect at the level of the gonads. [4][5]
Numerous studies have shown obesity has negative effects on reproductive success, from ovulation and conception to successful pregnancy and delivery. Women with obesity often experience dysfunction of the hypothalamic-pituitary-ovarian axis, which can lead to irregular menstrual cycles and anovulation. They also have higher levels of estrogen, which can lead to anovulation—secondary to hyperandrogenism—as well as endometrial hyperplasia. Some features of obesity and polycystic ovary syndrome (PCOS) overlap, such as insulin resistance and elevated androgens, but obesity has been shown to be an independent risk factor for reproductive complications such as spontaneous miscarriages. These hormonal imbalances impact egg quality, endometrial receptivity, and implantation, leading to reduced oocyte quality and quantity. [3]
“Numerous studies have shown obesity has negative effects on reproductive success, from ovulation and conception to successful pregnancy and delivery.”
Furthermore, the metabolic and inflammatory state associated with obesity can also affect endocrine factors that influence ovarian reserve. Studies show conflicting evidence on the impact of obesity on the success of in-vitro fertilization (IVF). Most studies conclude patients with obesity often need higher quantities of medications to stimulate the ovaries, and they have more cycle cancellations and fewer oocytes. The bigger debate among IVF studies is the live-birth rates of patients with obesity compared to patients with a normal BMI. Some show similar live-birth rates while others show increased live-birth rates in women with a normal BMI. [3]
Metwally et al [4] also analyzed studies of miscarriages in patients with obesity and drew attention to the extensive research on obesity and first-trimester miscarriages as well as obstetric complications. The authors noted women with obesity have a higher likelihood of experiencing gestational diabetes, hypertension, and pre-eclampsia, and a higher probability of having a cesarean delivery. Women with obesity are also more likely to have large gestational-age infants, which can increase the risk of birth complications, such as macrosomia, respiratory distress, and neonatal hypoglycemia. There is also a higher risk of postpartum hemorrhage, uterine infection, and a longer recovery time for the mother. Current recommendations across the board call for patients to receive preconception counseling that includes anesthetic and dietary guidance. [3]
“The authors noted women with obesity have a higher likelihood of experiencing gestational diabetes, hypertension, and pre-eclampsia, and a higher probability of having a cesarean delivery. Women with obesity are also more likely to have large gestational-age infants.”
Interventions to Enhance Reproductive Function
Treatments to improve reproductive function in patients with obesity range from lifestyle changes to surgery. Even small decreases in BMI have been shown to have substantial effects on reproductive success. Although more studies are needed on specific dietary and physical activity recommendations for patients with obesity and infertility, suggestions are often consistent with general health recommendations.
Several ovulation induction agents are used to assist patients with infertility. The most common first-line therapy is clomiphene citrate or metformin. Other obesity drugs prior to conception include sibutramine and orlistat. More research is needed to explore the safety of the latter two therapies in pregnancy. Bariatric surgery is also an option for patients who meet specific parameters. Studies show gastric banding surgery is well tolerated in pregnancy and is associated with a lower incidence of gestational diabetes and gestational hypertension. [3]
“Tracking data like cervical mucus, basal body temperature, hormone levels, and ovulation patterns can uncover problems that require further investigation to rule out PCOS, thyroid abnormalities, and diabetes, among others.”
Discussion
Research shows obesity has a significant impact on various aspects of female reproduction, including ovulation, menstrual function, fertility, and pregnancy outcomes. As the prevalence of obesity continues to rise across the globe, increased awareness and further research are needed. It is important for physicians to consider the impact of obesity on female reproductive function—both physically and psychologically—when counseling and treating patients. Medical professionals can educate patients through infertility support groups, and include information about fertility awareness-based methods (FABMs) and their potential benefits for women and couples with infertility. Tracking data like cervical mucus, basal body temperature, hormone levels, and ovulation patterns can uncover problems that require further investigation to rule out PCOS, thyroid abnormalities, and diabetes, among others. While these diseases do not always independently correlate with obesity, they may be overlooked in patients with infertility when focusing on BMI alone.
References
[1] NCD Risk Factor Collaboration (NCD-RisC). Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled analysis of 1698 population-based measurement studies with 19·2 million participants. Lancet. 2016;387:1377-1396.
[2] Fryar CD, Carroll MD, Afful J. Prevalence of overweight, obesity, and severe obesity among adults aged 20 and over: United States, 1960–1962 through 2017–2018. NCHS Health E-Stats, Centers for Disease Control and Prevention. 2020. Updated February 8, 2021. Accessed January 29, 2021. www.cdc.gov/nchs/data/hestat/obesity-adult-17-18/obesity-adult.htm
[3] Haslam, D., Sattar, N., & Lean, M. (2006). ABC of obesity: Obesity—Time to wake up. BMJ : British Medical Journal, 333(7569), 640-642. https://doi.org/10.1136/bmj.333.7569.640
[4] Metwally, M., Li, T. C., & Ledger, W. L. (2007). The impact of obesity on female reproductive function. Obesity Reviews, 8(6), 515-523.
[5] Moschos, S., Chan, J. L., & Mantzoros, C. S. (2002). Leptin and reproduction: a review. Fertility and sterility, 77(3), 433-444.
ABOUT THE AUTHOR
Adair McCabe, DO
Adair McCabe, DO is a second-year family medicine resident at Wellspan York Family Medicine in York, Pennsylvania. She completed her undergraduate education at the Pennsylvania State University and earned her medical degree at Edward Via College of Osteopathic Medicine. She enrolled in the FACTS elective to learn more about fertility awareness-based methods, a topic that is often overlooked today. She hopes to continue to share and utilize these methods with future patients, colleagues, family, and friends so they can play a significant role in their overall health and wellbeing.
