Preterm subtypes by immigrants’ length of residence in Norway: a population-based study

Table 2 Maternal and fetal health-related covariates in non-immigrants and in immigrants, by the length of residence, Norway 1990-2009

Non-immigrants		Immigrants	Immigrants by the length of residence (years)
Births (%)	868 832 (95.5%)	40 709 (4.5%)	20 074 (49.3%)	11 077 (27.2%)	4926 (12.1%)	4632 (11.4%)
			0-4	5-9	10-14	≥15
	%	%	%	%	%	%	P^a
Term gestational days, mean (SD)^b	282 (9.0)	280 (9.4)	280 (9.4)	280 (9.3)	279 (9.1)	278 (9.0)	<0.001
Gestational diabetes	0.7	2.6*	1.7	3.1	3.3	4.3	<0.001
Pregest. diabetes	0.5	1.1*	0.6	1.2	1.9	2.2	<0.001
Hypertensive disorders	5.2	3.6*	3.3	3.5	4.5	4.2	<0.001
Abruptio placentae	0.5	0.5	0.5	0.4	0.5	0.5	0.829
Placenta previa	0.2	0.3*	0.3	0.4	0.3	0.5	0.235
SGA^c	4.2	9.2*	9.7	8.1	8.0	10.3	<0.001
LGA^d	6.3	3.0*	2.5	3.5	4.2	2.8	<0.001
Major birth defects	2.4	2.4	2.4	2.5	2.3	2.6	0.714
Smoking^e							<0.001
Yes	18.9	1.6*	1.2	1.2	2.4	3.1
No	61.6	67.0	68.5	66.2	65.9	63.9
Not disclosed	19.5	31.4	30.3	32.6	31.7	33.0

*Different from non-immigrants (χ² test with P < 0.05). ^aAssociated to the length of residence, (χ² test with P < 0.05). ^bTerm gestational days with standard deviation was calculated for term infants with spontaneous labor onset. ^cSGA, small-for-gestational age infant, 5th percentile. ^dLGA, large-for-gestational age infant, 95th percentile. ^eSmoking was available from 1999 onwards.

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