Table 1. Odds ratios (ORs) for velamentous and marginal cord insertions according to maternal and pregnancy characteristics, based on 623,478 singleton pregnancies in Norway recorded between 1999 and 2009 and adjusted for maternal age and parity.

Maternal and pregnancy characteristics			Velamentous cord insertion						Marginal insertion
		Total (n)		Yes (n)	%	OR	95% CI		Yes (n)	%	OR	95% CI
Maternal age (years) ¥	<20	14932		222	1.49				1025	6.86
	20–24	92848		1318	1.42	1.06	0.92	1.23	5685	6.12	0.91		0.85	0.98
	25–29	204640		2890	1.41	1.06	0.92	1.21	12448	6.08	0.94		0.88	1.00
	30–34	206515		3162	1.53	1.22	1.06	1.40	13080	6.33	1.01		0.95	1.08
	35–39	89292		1601	1.79	1.50	1.30	1.74	6070	6.80	1.12		1.04	1.20
	40+	15205		306	2.01	1.75	1.46	2.09	1095	7.20	1.22		1.11	1.33
Parity *	0	256136		4292	1.68				17190	6.71
	1	221788		3228	1.46	0.81	0.78	0.85	13488	6.08	0.88		0.85	0.90
	2	102295		1415	1.38	0.73	0.68	0.77	6253	6.11	0.85		0.83	0.88
	3	29453		394	1.34	0.67	0.60	0.74	1734	5.89	0.80		0.76	0.84
	4+	13806		171	1.24	0.59	0.50	0.69	738	5.35	0.70		0.65	0.76
Assisted reproductive technology	No	613270		9127	1.49				38442	6.27
	Yes	10208		373	3.65	2.16	1.94	2.41	961	9.41	1.43		1.34	1.53
Fetal gender * ¥	Male	319257		4453	1.39				19978	6.26
	Female	302353		5045	1.67	1.20	1.15	1.25	19421	6.42	1.03		1.01	1.05
Smoking	No	412424		6367	1.54				27555	6.68
	Yes	102883		1827	1.78	1.19	1.12	1.25	6732	6.54	0.99		0.96	1.01
	NA	108171		1306	1.21	0.77	0.73	0.82	5116	4.73	0.69		0.67	0.71
Previous caesarean	No	316219		4406	1.39				18844	5.96
	Yes	51123		802	1.57	1.10	1.02	1.19	3369	6.59	1.10		1.06	1.14
Vaginal bleeding in pregnancy	No	595813		8707	1.46				37349	6.27
	Yes	27665		793	2.87	1.98	1.84	2.23	2054	7.42	1.20		1.14	1.25

CI, confidence interval; NA, not answered;

^¥not adjusted for maternal age;

^*not adjusted for parity.