Pregnancy incidence and outcome among patients with cervical intraepithelial neoplasia: a retrospective cohort study.

Objective: To investigate the effect of cervical intraepithelial neoplasia (CIN) treatment on incidence of pregnancy and pregnancy outcome.

Design: Retrospective cohort study.

Setting: Helsinki University Central Hospital, Finland, the sole reference centre in the Helsinki-Uusimaa region for women referred for colposcopy.

Population: A cohort of 6179 women treated for CIN between 1974 and 2001, and a randomly selected, age- and municipality-matched, reference population of 30,436 women.

Methods: Based on nationwide registers, all women were followed-up for pregnancy outcomes until death, emigration, sterilization, or until the end of 2004.

Main Outcome Measures: Incidence of any pregnancy, livebirths, miscarriages, extrauterine pregnancies, molar pregnancies, and terminations of pregnancies (TOPs) before and after CIN treatment, estimated by calculating hazard ratios (HRs) with stratified Cox regression and Poisson regression.

Results: After CIN treatment, both incidence of pregnancy (HR 1.20; 95% CI 1.15-1.26; P < 0.001) and incidence of livebirths (HR 1.12; 95% CI 1.06-1.18; P < 0.001) were higher among the treated women than among the reference population. Before treatment, only incidence of pregnancy had been elevated among those treated (HR 1.06; 95% CI 1.04-1.09; P < 0.001). The incidence of extrauterine pregnancies and of TOPs was significantly elevated among those treated both before and after CIN treatment.

Conclusions: No clear evidence emerged of adverse effects resulting from the CIN treatment itself, because the women treated had more pregnancies and more children than their reference population. TOPs and extrauterine pregnancies were more common among the treated women already before the CIN treatment.