Table 4.

Association between maternal dietary selenium intake and selenium intake from supplements 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 72 025)
Se intake from food§	0·97	0·94, 1·00	0·06	0·92	0·87, 0·98	0·012
Se intake from inorganic supplements§	1·02	0·99, 1·05	0·21	1·01	0·98, 1·05	0·41
Se intake from organic supplements§	0·99	0·95, 1·02	0·44	0·98	0·95, 1·02	0·32
Spontaneous deliveries (n 57 098)‖
Se intake from food§	0·95	0·91, 0·99	0·02	0·88	0·81, 0·96	0·003
Se intake from inorganic supplements§	1·05	1·01, 1·09	0·02	1·04	1·01, 1·03	0·08
Se intake from organic supplements§	0·99	0·94, 1·04	0·64	0·98	0·93, 1·03	0·37

^*Daily intake of Se from food and from supplements and HR for preterm delivery (22⁺⁰–36⁺⁶ weeks) in all subjects and in spontaneous deliveries only analysed with Cox regression. Number of preterm deliveries: 3618 of all 72 025 subjects and 2100 of the 57 098 spontaneous deliveries. Se intake from food and supplements was assessed with an FFQ in gestational week 22.

^†Adjusted for: maternal age, parity, smoking habits, alcohol consumption during pregnancy, maternal education, BMI, iodine intake in five categories, fibre intake, n-3 intake and total energy intake. Analyses for the different Se sources are also mutually adjusted in the adjusted model.

^‡HR per standard deviation of Se intake. Standard deviation for Se intake from food is 14·6 μg/d, from inorganic supplements 32·6 μg/d and from organic supplements 10·0 μg/d.

^§Measured in μg/d.

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