Abstract
OBJECTIVE: To determine the association between intrauterine device (IUD) use, timing of removal prior to pregnancy, and the risk of pre-eclampsia. DESIGN: A case-control study within the Clinical Practice Research Datalink, UK. SETTING: Medical record database in the UK. SAMPLE: Cases of pre-eclampsia (n = 2744) were identified among pregnancies resulting in singleton deliveries from 1993 to 2010. Four controls, or pregnancies unaffected by pre-eclampsia, were matched to each case on maternal age, general practice, and year of delivery. METHODS: Data on IUD use were obtained from patient records. The odds ratios (ORs) for the association between IUD and pre-eclampsia were adjusted for covariates identified a priori, and analyses were stratified by BMI and number of prior deliveries. MAIN OUTCOME MEASURES: Odds ratios (95% confidence intervals, 95% CIs) of pre-eclampsia in pregnancies among women with a history of IUD use, compared with women without a history of IUD use. RESULTS: Prior IUD use was associated with a reduced risk of pre-eclampsia (OR 0.76; 95% CI 0.58-0.98). The timing of removal in relation to the start of pregnancy showed an inverse association, with shorter intervals associated with a larger decrease in risk of pre-eclampsia. IUD removal within a year prior to pregnancy had an OR of 0.68 (95% CI 0.46-1.00). Among women with a prior delivery, the association between IUD use and pre-eclampsia was null. CONCLUSIONS: Intrauterine device use is associated with a small decreased risk of pre-eclampsia, specifically if removed within the year prior to conception. TWEETABLE ABSTRACT: A case-control study of pregnancies in the UK suggests a reduced risk of pre-eclampsia for former IUD users.