ADOLESCENT BODY-MASS INDEX AND INFERTILITY CAUSED BY OVULATORY DISORDER

OBJECTIVE: Our aim was to examine the association between body mass in dex at age 18 and subsequent primary ovulatory infertility. STUDY DESI GN: A nested case-control study was conducted within a cohort of 116,6 78 female registered nurses residing in 14 U.S. states. Cases comprise d 2527 married nulliparous nurses unable to become pregnant for at lea st 1 year because of ovulatory disorder; controls comprised 46,718 mar ried parous nurses with no history of infertility. The risk of ovulato ry infertility for women at different levels of body mass index at age 18 was compared with that for women whose body mass index at age 18 w as 20 to 21.9 (median for the cohort). Logistic regression was used to adjust for age at infertility or first birth, year of birth, age at m enarche, physical activity during ages 18 to 22, smoking at ages 15 to 19, ethnicity, alcohol use at ages 18 to 22, use of oral contraceptiv es before age 22, and diagnosis of diabetes mellitus. RESULTS: Multiva riate relative risks for infertility were: 1.2 (body mass index < 16), 1.1 (body mass index 16 to 17.9), 1.0 (body mass index 18 to 19.9), 1 .0 (referent body mass index 20 to 21.9), 1.1 (body mass index 22 to 2 3.9), 1.3 (body mass index 24 to 25.9), 1.7 (body mass index 26 to 27. 9), 2.4 (body mass index 28 to 29.9), 2.7 (body mass index 30 to 31.9) , and 2.7 (body mass index greater than or equal to 32). The relative risks for all categories of body mass index above 23.9 were statistica lly significantly elevated. Greater body mass index at age 18 was a pr edictor of ovulatory infertility in women with and without a diagnosis of polycystic ovary syndrome. CONCLUSION: These findings suggest that elevated body mass index at age 18, even at levels lower than those c onsidered to be obese, is a risk factor for subsequent ovulatory infer tility.