Background: It is known that women with Down syndrome can be fertile, but it is not known whether all women with Down syndrome are fertile or sub-fertile. The age at menopause for women with Down syndrome is lower compared to women without Down syndrome. Method: A cross-sectional study of 11 women was undertaken, in which the participating women had a blood sample taken and were also examined using transabdominal ultrasound scanning (ULS). Results: Definite signs of ovulation were evident in 2 women; hormone values in 5 women showed that they were in the luteal phase of the menstrual cycle; 1 woman was anovulatory; and in 1 woman it was not possible to judge the time of the menstrual cycle. Two of the women were postmenopausal according to medical information, ultrasound examination and hormone values. Conclusions: Safe contraceptives should be considered and offered if women with Down syndrome are engaging in sexual relations. Early menopause (before the age of 40 years) and the possibility of hormonal replacement therapy should be kept in mind. (Contains 1 table.)