Optimizing Reproductive Health in Women with Obesity and Infertility
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REVIEW CPD Optimizing reproductive health in women with obesity and infertility Matea Belan MSc, Soren Harnois-Leblanc MSc, Blandine Laferrère MD, Jean-Patrice Baillargeon MD MSc n Cite as: CMAJ 2018 June 18;190:E742-5. doi: 10.1503/cmaj.171233 nfertility, defined as a failure to achieve a pregnancy after at least 12 months of regular and unprotected sexual inter- KEY POINTS course, affects 15% of all couples in Canada.1 Costs associ- • Obesity is a known risk factor for female infertility and can affect Iated with assisted reproductive technologies are growing, such maternal and newborn health. that equitable access to high-quality reproductive care is a chal- • Expert guidance recommends that women with obesity and lenge for health care systems. Obesity is a known modifiable risk infertility adopt a healthy lifestyle aimed at losing weight before factor for female infertility and can affect maternal health; it also natural or medically assisted conception. puts the offspring’s health at risk both as a newborn and later in • Lifestyle interventions promoting weight loss have, in most life (cardiometabolic health).2 As such, addressing obesity in studies, shown improvement of fertility in women with obesity, women seeking to become pregnant would be prudent, espe- mainly increasing the chance of spontaneous pregnancy. cially given that 25% of Canadian women of reproductive age are • Lifestyle modification is the preferred approach to preconception overweight (body mass index [BMI] 25–30) and 19% are obese weight loss, over bariatric surgery or pharmacologic agents. (BMI > 30).3 We review evidence on the effects of obesity on women’s fertility, recommendations regarding obesity manage- ment in women with infertility, and evidence of the benefits of women, there was a linear decline of 4% in the chances of a weight loss and lifestyle changes for fertility and pregnancy out- spontaneous pregnancy for each increase of one point in the BMI comes (Box 1 outlines our search strategy). score in obese women.9 Yet there are few existing cohort studies including obese women without PCOS, since the condition is What is the relation between obesity and fairly common, clinically exacerbated by obesity and the most women’s fertility? common cause of infertility in women.10,11 In women seeking fertility treatments, obesity was associated The risk of infertility is increased by 78% and 27% in women of with a decrease in pregnancy12,13 and live-birth rates.13 Further- childbearing age with obesity and overweight, respectively, as more, to achieve a pregnancy, women with obesity undergoing compared with women of normal weight (BMI 18.5–25).4 Obesity fertility treatments (intrauterine insemination or in vitro fertiliza- can negatively affect women’s fertility via menstrual and ovula- tion) are more likely to need higher doses of gonadotropin and tory disorders. Such disorders include polycystic ovary syndrome have more cancelled cycles12,14 and lower embryo quality.15 A (PCOS), the most common cause of female infertility, affecting meta-analysis found no associations between being overweight 6% to 10% of women of child-bearing age. Insulin resistance is and risks of ovarian hyperstimulation syndrome and multiple considered to play an important role in the association between pregnancies compared with normal-weight women, but reported PCOS and obesity, because elevated circulating levels of insulin a slight decline in the live-birth rate following assisted reproduc- stimulate androgen production by the ovaries.5 Moreover, higher tive technologies in obese women (odds ratio [OR] 0.90, 95% levels of circulating triglycerides and fatty acids, which are asso- confidence interval [CI] 0.82–1.00).11 ciated with obesity and insulin resistance, may directly induce androgen production in predisposed women.6 Obesity, especially What is the effect of maternal obesity at central obesity, exacerbates clinical features of PCOS:7,8 obesity conception on offspring? has a negative impact on the effectiveness of fertility treatments and confers a higher risk of pregnancy complications7 and Although fertility treatments are becoming more efficient in cardio metabolic diseases.5 However, the negative effects of obe- overcoming the effects of obesity on women’s fertility, prepreg- sity on women’s reproductive health are observed even in nancy and gestational obesity are serious risk factors for preg- women with no apparent ovulatory or menstrual dysfunctions. In nancy and neonatal complications. According to an extensive a large prospective cohort, with more than 3000 eumenorrheic systematic review of published reviews, pregnant women with E742 CMAJ | JUNE 18, 2018 | VOLUME 190 | ISSUE 24 © 2018 Joule Inc. or its licensors scribing any fertility treatments, according to guidance from Box 1: Evidence used in this review expert bodies.20–22 In 2010, the ESHRE pointed out that the goal of We searched PubMed to find relevant reviews on the subject 5% weight loss should not be mandatory to access fertility treat- published within the past 10 years. We used a small number of ments. However, lifestyle modifications before fertility treat- REVIEW keywords to broaden our research, mainly to reach all types of ments can improve success of the treatments, prevent preg- studies and interventions in obesity and fertility: [“weight loss” OR nancy and neonatal complications, and limit associated costs.20 “weight management”] AND [“lifestyle” OR “multidisciplinary intervention/program”] AND [“fertil*” OR “infertil*” OR “pregnan*”]. The search for these keywords was limited to titles Do lifestyle modifications and weight loss and abstracts. Corresponding to our criteria, a total of 78 reviews improve fertility outcomes in women with were proposed, of which we included the 6 most recent and obesity and infertility? relevant to the subject. We added 14 original research articles because they were considered milestone studies in their field. Ten articles representing guidelines from health organizations relevant Weight loss recommendations during the preconception period to the subject were also included in this review. in women with obesity and infertility are primarily based on studies conducted in women with PCOS, among whom studies have shown that lifestyle modification can improve metabolic obesity have significantly higher odds of gestational diabetes (OR and reproductive outcomes.24 Women with PCOS could benefit 3.01 to 5.55), preeclampsia (OR 2.93 to 4.14), antenatal (OR 1.43) more from weight loss than women without PCOS because, for and postpartum depression (OR 1.30), and cesarean delivery (OR the same degree of obesity, they tend to have higher central obe- 2.01 to 2.26), compared with normal-weight women.2 Newborns sity and insulin resistance,25 which are linked to adverse meta- born to mothers with obesity are at a higher risk of preterm birth bolic and reproductive outcomes.5 However, obesity and insulin (< 32 weeks’ gestation; adjusted OR 1.33, 95% CI 1.12–1.57), mac- resistance are important factors in the disturbance of the repro- rosomia (> 4500 g; OR 3.23, 95% CI 2.39–4.37), perinatal death ductive axis in women without PCOS as well.26 (relative risk 1.34, 95% CI 1.22–1.47) and congenital anomalies — A systematic review of 11 observational studies and random- including neural tube defects (OR 2.24, 95% CI 1.86–2.29) and ized controlled trials (RCTs), most of which included women cardiovascular anomalies (OR 1.30, 95% CI 1.12–1.51) — com- undergoing in vitro fertilization treatments, found that the inci- pared with newborns born to mothers with normal prepregnancy dence of spontaneous pregnancy and live birth was increased in weight.2,16 In addition, maternal prepregnancy BMI and excessive women allocated to a lifestyle intervention compared with con- gestational weight gain are consistently associated with early trols.27 Two three-arm RCTs involving women with obesity and development of obesity and diabetes in the offspring.17 This risk PCOS who were previously resistant28 or not29 to clomiphene may be carried through epigenetic mechanisms and perpetuates citrate reported that the combination of clomiphene citrate with the transgenerational vicious cycle of obesity and cardiometa- lifestyle intervention increased the women’s ovulation rates as bolic diseases.18 compared with clomiphene citrate alone. There are few studies that have assessed the benefits of life- How should physicians advise overweight and style interventions as first-line therapy in the general population of obese women who seek infertility treatment? women with obesity and infertility. An Australian research group reported in 1998 the fertility effects of a program that consisted of As outlined above, extensive data support strong associations weekly group sessions with supervised physical activity practices between obesity and infertility in women, as well as notable and workshops covering different nutritional topics.30 After pregnancy and neonatal complications for obese women. 12 months of follow-up, 90% of women who completed the inter- Accordingly, targeting women with obesity before conception vention resumed spontaneous ovulation, 78% conceived, of which may be essential to reduce the burden of infertility and costs of 33% conceived spontaneously, and 67% delivered a live newborn, fertility treatment, as well as obesity and cardiometabolic dis- as compared with none of the women in the control group. eases. As such, physicians should warn women with obesity A recent multicentre RCT