Menstrual cycles and basal body temperature curves in women with Down syndrome.

Menstrual histories were obtained from 51 females with Down syndrome between the ages of 10-27 years. The average age at onset of menstruation of girls in our study was 12 years, 6 months. Seventy-six percent of them had regular menstrual cycles with an average length of menstrual flow of 4 days, and most menstrual cycles lasted 25-30 days. Eight of the women with regular menstrual cycles provided 26 basal body temperature charts. When basal body temperatures were graphed using the smoothed-curve technique, 88.5% had biphasic curves indicative of an ovulatory pattern.