Table 3.

Crude and adjusted hazard ratios^* (HRs) of fetal death^† (n=492) among 113,331 women who gave birth to singletons in Norway in 2009 or 2010, according to combinations of influenza vaccination status and being pregnant in the main wave of the 2009 influenza pandemic^‡.

Pregnant during the pandemic	Vaccinated in pregnancy	Pregnancy days at risk§	Crude		Adjusted□
			HR	(95% CI)	HR	(95% CI)
No	No	10,414,633	1	-	1	-
No	Yes	7402	-	-	-	-
Yes	No	5,527,619	1.21	(1.00 – 1.48)	1.25	(1.02 – 1.55)
Yes	Yes	3,020,750	1.02	(0.79 – 1.32)	1.10	(0.84 – 1.45)

^*Hazard ratios were estimated with gestational day as the time metric.

^†Fetal death was any fetal death/stillbirth after 12 completed pregnancy weeks.

^‡At least one day in pregnancy between 1 October and 31 December 2009.

^§Each woman may contribute days at risk as both unexposed and exposed.

^□Adjusted for age, parity, marital status, use of nutritional supplements in pregnancy, smoking in pregnancy, history of earlier fetal death, and chronic health conditions (asthma, hypertension, kidney disease, rheumatoid arthritis, epilepsy, thyroid disease, or diabetes).