Return of fertility in nulliparous women after discontinuation of the intrauterine device: comparison with women discontinuing ether methods of contraception

Objective To clarify the effect of the using the intrauterine device on fer tility in nulliparous women. Design Prospective cohort study of two groups of nulliparous women, one rec ruited while using an intrauterine device and the other while using an oral contraceptive. Setting Seventeen family planning clinics in England and Scotland. Sample 1071 nulliparous, married women, aged 18-40 years, 558 of whom contr ibuted information to the main objective of the study. Methods The women were recruited between 1982 and 1985 and followed up annu ally to 1994. Dates and reasons for any contraceptive method changes (which were most frequently to barrier methods) were recorded, together with the outcome of any pregnancies, at each follow up. Main outcome measures The number of nulliparous women giving birth at term after stopping contraception (oral contraceptive, intrauterine device or ba rrier method) in order to conceive. Results Women who stopped using a barrier method to achieve a planned pregn ancy conceived most quickly: 54%, were delivered after one year vs 39% of i ntrauterine device and 32% of oral contraceptive users (log rank P = 0.002) , There was no association between fertility and duration of oral contracep tive use: However, short term intrauterine device users (< 42 months) showe d a fertility pattern more favourable than seen in those discontinuing oral contraceptives, with increasing duration of intrauterine device use being associated with decreasing fertility (linear trend P = 0.005); the fertilit y of women who had used the intrauterine device for 78 + months was the mos t impaired (28% were delivered by 12 months vs 46% of short term users; at 36 months the corresponding figures were 79% vs 91%). This association rema ined after adjusting for potential confounding factors, including maternal age, husband's social class, and history of gynaecological illnesses, facto rs which themselves had independent associations with fertility. Conclusions Long term intrauterine device use in nulliparous women appears to be associated with an increased risk of fertility impairment.