Fecundity among women with polycystic ovary syndrome (PCOS)-a population-based study

STUDY QUESTION: Does the long-term fecundity of women with polycystic ovary syndrome (PCOS) differ from those without PCOS? SUMMARY ANSWER: Cumulative probability of childbirth is similar between women with and without PCOS. WHAT IS KNOWN ALREADY: PCOS is the main cause of anovulatory infertility in women after menarche. Previous studies indirectly suggest that fecundity in women with PCOS over the longer term may not be lower than in women PCOS. STUDY DESIGN, SIZE, DURATION: This is a population-based study using four linked Swedish national registries. A total of 45 395 women with PCOS and 217 049 non-PCOS women were included. Follow-up began at the age of 18 years and continued for a maximum of 26 years, from 1989 to the end of 2015. Childbirth was the main outcome, as identified from the Medical Birth Register. PARTICIPANTS/MATERIALS, SETTING, METHODS: All women born between 1971 and 1997 who were identified with a PCOS diagnosis in the Swedish Patient Registry between I January 2001 and 31 December 2016 were included in the study population. Five controls per women with PCOS were randomly drawn from the Total Population Registry. The control women were born in the same year and living in the same municipality as the patient. The fecundity ratio (FR) was calculated by clustered Cox regression using a robust variance, adjusted for maternal birth period, country of birth and level of education. MAIN RESULTS AND THE ROLE OF CHANCE: The cumulative probability of childbirth was 80.2% (95% CI, 79.5-80.9%) in women with PCOS and 78.2% (95% CI, 77.9-78.5%) in those without PCOS. Adjusted FR was 0.81 (95% CI, 0.80-0.82) for first childbirth and 0.58 (95% CI, 0.57-0.60) for first childbirth following a spontaneous pregnancy. The FR for second childbirth was 0.79 (95% CI, 0.77-0.80). Women with PCOS had more than one child less frequently than the comparison group. Within the PCOS group, early age at diagnosis, later birth year, Nordic country of origin and low educational