Table 6.

Association between maternal selenium blood concentration in mid-pregnancy and risk of preterm delivery^*

(Hazard ratios (HR) and 95 % confidence intervals)

	Unadjusted			Adjusted†
	HR‡	95 % CI	P	HR‡	95 % CI	P
All subjects (n 2638)
Blood Se concentration§	0·91	0·72, 1·15	0·42	0·93	0·74, 1·18	0·93
Spontaneous deliveries (n 2177)‖
Blood Se concentration§	0·91	0·69, 1·21	0·52	0·92	0·69, 1·22	0·56

^*Maternal blood Se concentrations (μg/l) and HR for preterm delivery (22⁺⁰–36⁺⁶ weeks) in all subjects with Se blood measurements (n 2638) and in spontaneous deliveries only (n 2177) analysed with Cox regression. Number of preterm cases: 80 of all 2638 subjects and 55 of the 2177 spontaneous deliveries. Blood Se concentrations were measured in whole blood collected in gestational week 17–18.

^†Adjusted for maternal age, parity, smoking habits, alcohol consumption during pregnancy, maternal education and BMI.

^‡HR per standard deviation (23·4 μg/l) of blood Se concentrations.

^§Measured in μg/l.

^‖Iatrogenic deliveries have been censored in the regression model.