. 2018 Apr 19;8:6300. doi: 10.1038/s41598-018-24634-2

Table 2.

Gestational age and risk of preterm delivery by dizygotic twin pair type (reference group boy-boy pairs).

	Boy-boy pairs	Boy-girl pairs	RC^a/OR^b (95% CIs)	p-value	Girl-girl pairs	RC^a/OR^b (95% CIs)	p-value
	n = 6204	n = 11,660	RC^a/OR^b (95% CIs)	p-value	n = 6059	RC^a/OR^b (95% CIs)	p-value
Gestational age (SD) weeks	36.63 ± 2.57	36.74 ± 2.51	0.13(0.06, 0.21)^a	0.001	36.87 ± 2.48	0.20(0.11, 0.28)^a	<0.001
Delivery before 37 weeks	2383 (38.4)	4274(36.7)	0.92(0.86, 0.98)^b	0.007	2134(35.2)	0.88(0.82, 0.95)^b	0.001
Delivery before 34 weeks	712(11.5)	1223(10.5)	0.89(0.81, 0.99)^b	0.024	564(9.3)	0.80(0.71, 0.90)^b	<0.001
Delivery before 31 weeks	182(3.0)	305(2.7)	0.88(0.73, 1.06)^b	0.165	145(2.5)	0.82(0.66, 1.02)^b	0.078

Data are mean ± standard deviation or number of pairs (%).

^aRegression coefficient (RC) for the difference in gestational age.

^bOdds ratios (OR) for the risk of preterm delivery.