Table 4. Unadjusted and age-adjusted hazard ratios and 95% confidence intervals for the association between Letigen^* use and spontaneous abortion (SAB) in the Danish National Birth Cohort (1996–2002).

			Unadjusted		Age adjusted†
Timeframe of exposure§	SAB	Fetus-days$	HR	(95% CI)	HR	(95% CI)
None	4,408	6,656,492	1.0	ref	1.0	ref
Pre-conception only	13	17,954	1.0	0.6; 1.6	1.0	0.6; 1.7
Both pre-conception and early pregnancy	17	21,657	1.0	0.6; 1.7	1.1	0.7; 1.7
Early pregnancy only	5	2,796	2.6	1.1; 6.5	2.7	1.1; 6.6

^*Letigen is composed of 20 mg ephedrine and 200 mg caffeine.

^†Adjusted for maternal age using the following categories: 15–19, 20–24, 30–34, 35–39, 40–46 with 25–29 as the referent.

^§Pre-conception includes the 4 weeks prior to last menstrual period through gestational age 2 completed weeks; early pregnancy includes gestational age 3–13 completed weeks.

$Observed fetus days at risk (i.e. time from entry to outcome, censoring, or end of risk period).

Abbreviations: HR, hazard ratio; CI, confidence interval.