Table 2.

Maternal dietary selenium intake and maternal blood selenium concentration according to maternal characteristics^†

(Numbers of subjects and percentages; medians and interquartile ranges (IQR))

		Se intake from food (µg/d)					Blood Se concentration (µg/l)
		n	%	Median	IQR	P *	n	%	Median	IQR	P *
Total		72 025	100	53	44–62		2638
Maternal age (years)	<25	8284	12	50	41–62	<0·0001	220	8	98	86–112	<0·0001
	25–29	24 411	34	52	43–62		947	36	102	88–116
	30–34	30 524	42	53	45–63		1180	45	102	90–118
	>34	8806	12	54	46–64		291	11	105	91–122
Pre-pregnancy BMI (kg/m2)	<18·5	2143		53	44–64	<0·0001	81	3	104	91–116	0·024
	18·5–24·9	46 163	64	53	45–63		1703	65	102	90–119
	25–30	15 189	21	52	43–62		611	23	101	88–116
	>30	6657	9	51	42–61		194	7	100	86–114
	Missing	1873	3	53	44–62		49	2	101	93–113
Parity	0	38 310	53	52	43–62	<0·0001	1515	57	104	91–119	<0·0001
	1	21 650	30	53	44–62		755	29	101	88–115
	2	9700	13	54	45–63		317	12	100	87–115
	3+	2306	3	54	45–64		50	2	91	81–103
	Missing	59	0	56	45–64		1	0	112	112–112
Preterm birth	Yes	3618	5	52	44–62	0·022	80	3	103	90–114	0·769
	No	68 407	95	53	44–62		2558	97	102	89–117
Gestational age groups	Early preterm (GW 22–33)	952	1	51	43–61	0·026	8	0	92	81–102	0·434
	Late preterm (GW 34–36)	2666	4	53	44–62		72	3	104	93–115
	Early term (GW 37–38)	11 660	16	53	44–63		410	16	102	89–117
	Late term (GW 39–42)	56 747	79	53	44–62		2148	81	102	89–117
Maternal education (years)	<13	22 424	31	51	42–62	<0·0001	677	26	100	86–114	<0·0001
	13–16	29 854	41	53	44–62		1248	47	101	88–116
	>16	18 202	25	54	46–64		655	29	107	94–122
	Missing	1545	2	51	42–62		58	2	98	87–115
Smoking habits	Never	65 765	91	53	44–62	<0·0001	2462	93	102	90–118	0·001
	Occasionally	1953	3	52	43–63		63	2	99	90–113
	Daily	3900	5	52	42–62		103	4	95	85–110
	Missing	407	1	52	43–62		10	0	97	90–114
Alcohol consumption	No	64 079	89	53	44–62	<0·0001	2329	88	102	89–117	0·02
	Yes	7946	11	54	46–63		309	12	104	92–120
Iodine intake (µg/d)	<82	14 389	20	42	35–49	<0·0001	510	19	101	88–118	0·50
	82–108	14 389	20	49	42–56		554	21	103	90–118
	108–135	14 389	20	52	45–60		523	20	102	89–117
	135–174	14 389	20	57	50–65		554	21	103	91–117
	>174	14 389	20	65	56–75		497	19	101	88–116
n-3 intake (g/d)	<0·25	26 547	37	46	38–54	<0·0001	986	37	98	87–113	<0·0001
	0·25–0·47	24 548	34	53	46–61		977	37	105	91–118
	>0·47	20 851	29	62	53–72		675	26	106	92–120
Protein intake (g/d)	<76	24 008	33	42	36–48	<0·0001	868	33	102	88–118	0·79
	76–93	24 009	33	53	47–59		907	34	102	89–117
	>93	24 008	33	65	58–74		863	32	102	90–117
Fibre intake (g/d)	<26	24 008	33	43	37–51	<0·0001	870	33	101	88–116	0·04
	26–35	24 009	33	53	46–60		933	35	102	89–117
	>35	24 008	33	63	55–72		835	32	104	90–118
Energy intake (MJ/d)	<8390	24 008	33	44	37–50	<0·0001	913	35	103	90–118	0·21
	8390–10 460	24 009	33	53	46–60		893	34	102	89–117
	>10 460	24 008	33	63	55–73		832	32	101	89–117

GW, gestational week.

^* P value obtained with the Mann–Whitney U test for two groups and the Kruskal–Wallis test for more than two groups.

^†Amount of daily Se intake from food (FFQ data) and concentration of Se in blood in mid-pregnancy, according to maternal characteristics, from 72 025 participants in the Norwegian Mother and Child Cohort Study. Se intake from food was assessed with an FFQ in gestational week 22. Blood Se concentration was measured in whole blood collected in GW 17–18 in a subsample of 2638 of the 72 025 participating mothers.