Paternal characteristics associated with maternal periconceptional use of folic acid supplementation

Table 3 Relative risks (RRs) with 95% confidence intervals (95% CI) of adequate maternal periconceptional folic acid supplement use (before and during pregnancy) by combining maternal and paternal education in 683,785 pregnancies, Norway, 1999–2010

		Adequate folic acid use		Unadjusted		Adjusted ^a
Maternal education	Paternal education	Yes	No	RR*	95% CI	RR*	95% CI
Compulsory education	Compulsory education	2557	48,326	0.46	0.43–0.50	0.53	0.50–0.57
	Intermediate education	4758	52,693	0.77	0.72–0.81	0.76	0.72–0.81
	Tertiary education	1292	10,651	1.00	Reference	1.00	Reference
	Missing information	208	4994
Intermediate education	Compulsory education	5079	43,708	0.60	0.57–0.62	0.66	0.64–0.68
	Intermediate education	18,055	116,378	0.77	0.75–0.79	0.81	0.79–0.83
	Tertiary education	7477	35,269	1.00	Reference	1.00	Reference
	Missing information	426	3928
Tertiary education	Compulsory education	3805	17,985	0.70	0.67–0.72	0.75	0.73–0.77
	Intermediate education	22,150	80,373	0.86	0.85–0.87	0.88	0.87–0.89
	Tertiary education	42,541	126,896	1.00	Reference	1.00	Reference
	Missing information	747	3539
Missing data (maternal education)		28,179	1771

^aAdjusted for paternal age (< 20, 20–24, 25–29, 30–34, 35–39, 40+), year of childbirth (1999–2010 (continuous)), paternal country of origin (Norway, high income countries, low/middle income countries), stratified by maternal education
*p values for interaction between maternal and paternal education were calculated by likelihood-ratio tests (unadjusted p value < 0.001; adjusted p value < 0.001)

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