Abstract: Objective：To investigate the effect of intrauterine device (IUD) on female fertility. Methods：From July 1, 2016 to September 30, 2017, two-way cohort study was used to observe the pregnancy within one year after using IUD as the observation cohort (1 361 cases) and condom women as the control cohort (1 307 cases) after giving birth to one child. The cumulative pregnancy rate of one year was calculated and the Cox proportional hazard model was used for multivariate analysis. Results：The average days of pregnancy in IUD group and control group were (144.1±96.86) days and (122.5±91.33) days, respectively. There was statistically significant difference between the two groups (P＜0.05). The cumulative pregnancy rate in IUD group was lower than that in control group. The difference was statistically significant (P＜0.05). The cumulative pregnancy rate of one year after removal of IUD for less than 5 years was 0.866 times higher than that of condom group (95%CI: 0.788～0.952). Multivariate Cox regression analysis showed that using of high copper IUD had a slighter effect on pregnancy (HR=0.826, 95%CI: 0.720～0.947) than using condoms. Conclusions：The cumulative pregnancy rate of one year after removal of high copper IUD was lower than that in condom group, and the pregnancy time was longer. It is suggested that if the subjects with using high copper IUD have plans for reproduction in the near future, IUD should be removed as early as possible to prepare for fertility.

Key words: Intrauterine devices, Pregnancy rate, Fertility, Cohort studies