Abnormal uterine bleeding patterns detected among women with obesity, hyper- and hypothyroidism, endometriosis in Apple Women’s Health Study


In an effort to identify abnormal bleeding patterns and their prevalence and confirm existing and expected associations, a study was conducted as part of Apple’s larger Women’s Health Study.

The Apple Women’s Health Study included participants from November 2019 through July 2021 who contributed menstrual tracking data and did not report pregnancy, lactation, use of hormones, or menopause. The participants totaled 18,875 with a mean age of 33 (standard deviation (SD), 8.2) years. As for uterine bleeding patterns, 4 abnormal patterns were evaluated—irregular menses, infrequent menses, prolonged menses, and irregulat intermenstrual bleeding (spotting). According to the report in the American Journal of Obstetrics and Gynecology, the end results excluded inaccurate or incomplete digital records.

Data were collected for the 18,875 participants, which included a mean body mass index of 29.3 (SD 8.0), and with nearly 70% identifying as White, non-Hispanic.

As for the results, abnormal uterine bleeding was found in 16.4% of participants (n=3103, 95% CI, 15.9-17.0) after inaccurate tracking was confirmed; 2.9% had irregular menses, 8.4% had infrequent menses, 2.3% had prolonged menses, and 6.1% had spotting. Black participants, the results showed, had a 33% higher prevalence of infrequent menses when compared with White non-Hispanic participants after controlling for age and body mass index. Obesity also played a role in the prevalence of infrequent menses, increasing in class 1, 2, and 3 obesity (class 1: body mass index of 30 to 34.9; prevalence ratio, 1.31; class 2: body mass index of 35 to 39.9; prevalence ratio, 1.25; class 3: body mass index >40; prevalence ratio, 1.51) after controlling for age and race/ethnicity. Participants in the class 3 obesity cate3gory had 18% higher prevalence of abnormal uterine bleeding compared with healthy weight participants (prevalence ratio, 1.18).

Participants with polycystic ovarian syndrome (PCOS) had 19% higher prevalence of abnormal uterine bleeding compared with participants without this condition (prevalence ratio, 1.19). Participants with hyperthyroidism (prevalence ratio, 1.34) and hypothyroidism (prevalence ratio, 1.17) had a higher prevalence of abnormal uterine bleeding, as did those reporting endometriosis (prevalence ratio, 1.28), cervical dysplasia (prevalence ratio, 1.20), and fibroids (prevalence ratio, 1.14).


  1. Zhang CY, Li H, Zhang S, et al. Abnormal uterine bleeding patterns determined through menstrual tracking among participants in the Apple Women’s Health Study. American Journal of Obstetrics and Gynecology. Published online October 2022. doi:10.1016/j.ajog.2022.10.029
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