TABLE 4.

Association Between Chlamydia Status and Getting Pregnant by Exposure Time Intervals

	Pregnancies	Time	Crude HR			aHR
	n*	Person-Years†	HR	95% CI	P	aHR	95% CI	P
1. Years after sexual debut 0–6
Chlamydia negative	536	30,207	1			1
Chlamydia positive	148	2659	2.33	1.92–2.81	<0.01	1.54	1.26–1.89	<0.01
No infection	536	30,207	1			1
1 infection	123	2394	2.24	1.83–2.74	<0.01	1.50	1.21–1.86	<0.01
Multiple infections	25	265	3.07	2.16–4.37	<0.01	1.88	1.24–2.85	<0.01
2. Years after sexual debut 7–10
Chlamydia negative	637	17,103	1			1
Chlamydia positive	268	4047	1.37	1.18–1.58	<0.01	1.42	1.22–1.66	<0.01
No infection	637	17,103	1			1
1 infection	203	3295	1.33	1.14–1.56	<0.01	1.37	1.18–1.62	<0.01
Multiple infections	65	752	1.50	1.15–1.96	<0.01	1.67	1.25–2.24	<0.01
3. Years after sexual debut 11–13
Chlamydia negative	859	10,217	1			1
Chlamydia positive	229	3228	0.77	0.67–0.89	<0.01	0.93	0.80–1.07	0.32
No infection	859	10,217	1			1
1 infection	183	2536	0.79	0.68–0.92	<0.01	0.93	0.80–1.08	0.35
Multiple infections	46	692	0.68	0.51–0.90	0.01	0.93	0.69–1.25	0.63
4. Years after sexual debut 14–23
Chlamydia negative	1,690	12,447	1			1
Chlamydia positive	564	4637	0.86	0.78–0.95	>0.01	1.00	0.90–1.10	0.96
No infection	1,690	12,447	1			1
1 infection	443	3594	0.87	0.78–0.97	0.01	0.99	0.89–1.10	0.81
Multiple infections	121	1043	0.88	0.68–1.04	0.11	1.05	0.85–1.30	0.65

Chlamydia positive was defined as a positive NAAT test outcome in the CSI study (CSI-NAAT), and/or the presence of chlamydia IgG and/or a self-reported chlamydia infection. For these analyses, multiple imputations were used to estimate time of first chlamydia infection in women without a known first year of chlamydia infection. Models were adjusted for age, education level, migration background and number of lifetime partners.

*Complete cases.

^†Person-years of complete cases.

aHR indicates adjusted hazard ratio; CI, confidence interval; HR, hazard ratio.