Effect of extended oral contraception use on the prevalence of fetal trisomy 21 in women aged at least 35 years.

OBJECTIVE: To study factors influencing the number of ovulations in reproductive life as risk factors for common trisomies.

METHODS: The present observational study examined data from genetic counseling sessions performed at the 1st Department of Obstetrics and Gynecology, Semmelweis University, Budapest, Hungary, between September 1, 2013, and September 1, 2015, and retrieved data on patients of advanced maternal age (≥35 years) who had fetal trisomy 21, 18, or 13 confirmed. Consecutive patients of advanced maternal age with genetic amniocentesis-confirmed healthy fetal karyotypes were also included as a control group. Medical record details were confirmed through telephone interviews with patients; the estimated ovulation number was calculated and compared among patients, as were factors contributing to the number of ovulations each patient had.

RESULTS: Data from 12 776 genetic counseling situations were examined; 35 patients with fetal trisomies and 100 patients in the control group were interviewed. Shorter mean length of oral contraceptive pill use before trisomic pregnancy (P<0.001) and a higher estimated ovulation number (P=0.012) were identified among patients with pregnancies with fetal trisomies.

CONCLUSION: Fewer ovulatory cycles, potentially resulting from longer oral contraceptive pill use, was associated with healthy fetal karyotypes among patients of advanced reproductive age.