Table 4.

Odds ratios and 95% confidence intervals for the association between IUD use and pre-eclampsia, stratified by prior deliveries in the CPRD

	Cases n = 2744 n (%)	Controls n = 11 156 n (%)	OR (95% CI) for pre-eclampsia
			Unadjusted	Adjusted*
No prior delivery
IUD	35 (1.3)	139 (1.3)	0.68 (0.47–0.99)	0.64 (0.44–0.93)
No IUD	1956 (71.3)	5277 (47.3)	1.00 (ref.)	1.00 (ref.)
≥1 prior delivery
IUD	48 (1.8)	348 (3.1)	1.06 (0.77–1.44)	1.03 (0.75–1.42)
No IUD	705 (25.7)	5392 (48.3)	1.00 (ref.)	1.00 (ref.)
	Subjects with ≥10 years of follow-up
	Cases n = 590 n (%)	Controls n = 2210 n (%)	OR (95% CI) for pre-eclampsia
			Unadjusted	Adjusted*
No prior delivery
IUD	8 (1.4)	33 (1.5)	0.61 (0.28–1.32)	0.56 (0.25–0.99)
No IUD	401 (68.0)	1002 (45.1)	1.00 (ref.)	1.00 (ref.)
≥1 prior delivery
IUD	10 (1.7)	78 (3.5)	0.83 (0.42–1.64)	0.86 (0.43–1.72)
No IUD	171 (29.0)	1108 (49.9)	1.00 (ref.)	1.00 (ref.)

^*Adjusted for maternal age, BMI (with imputation), smoker (with imputation), induced abortion, fertility problems, and pre-existing diabetes.