Table 2. Unadjusted First-year and 3-year Pearl Indices According to Age, Parity Status and BMI (Full Analysis Set).

		LNG-IUS 8				LNG-IUS 13
		Number of pregnancies/number of subjects	Relevant exposure* [WY]	Pearl Index	95% CI	Number of pregnancies/number of subjects	Relevant exposure* [WY]	Pearl Index	95% CI
Analysis period	Age category
First year	18–25 years	1/566	455.62	0.22	0.01–1.22	1/564	473.33	0.21	0.01–1.18
	26–35 years	4/866	762.15	0.52	0.14–1.34	1/888	779.45	0.13	0.00–0.71
3-year	18–25 years	4/566	1114.21	0.36	0.10–0.92	2/564	1207.19	0.17	0.02–0.60
	26–35 years	6/866	1944.41	0.31	0.11–0.67	8/888	2004.17	0.40	0.17–0.79
Analysis period	Parity status
First year	Nulliparous	2/556	446.88	0.45	0.05–1.62	0/574	473.39	0.00	0.00–0.78
	Parous	3/876	770.90	0.39	0.08–1.14	2/878	779.38	0.26	0.03–0.93
3-year	Nulliparous	4/556	1110.63	0.36	0.10–0.92	3/574	1205.33	0.25	0.05–0.73
	Parous	6/876	1947.99	0.31	0.11–0.67	7/878	2006.03	0.35	0.14–0.72
Analysis period	BMI category
First year	<30 kg/m2	4/1187	1009.73	0.40	0.11–1.01	1/1198	1038.10	0.10	0.00–0.54
	≥30 kg/m2	1/244	207.13	0.48	0.01–2.69	1/250	211.13	0.47	0.01–2.64
3-year	<30 kg/m2	9/1187	2547.32	0.35	0.16–0.67	6/1198	2664.82	0.23	0.08–0.49
	≥30 kg/m2	1/244	509.34	0.20	0.00–1.09	4/250	538.41	0.74	0.20–1.90

* Relevant exposure was calculated from the total exposure minus the time in which back-up contraception was used or sex hormones were taken for other reasons.

BMI, body mass index; CI, confidence interval; WY, woman-year (1 WY = 365 days); LNG-IUS 8; levonorgestrel intrauterine system total content 13.5 mg (average approx. 8 μg/24 hours over the first year); LNG-IUS 13, levonorgestrel intrauterine system total content 19.5 mg (average approx. 13 μg/24 hours over the first year).