Table 3.

Pregnancy outcomes of twins reduced to singletons versus primary twins.

	Primary twins(n=2788)	Twins reduced to singleton(n=126)	Unadjusted P Value	Unadjusted OR(95% CI)	Adjusted P Value	Adjusted OR(95% CI)
GA at delivery	37.00 (35.71-38.00)	38.79 (37.46-39.43)	<0.001	–	<0.001	–
Delivery<32weeks	126 (4.5)	5 (4.0)	0.770	0.87 (0.35-2.17)	0.743	0.97 (0.81-1.17)
Delivery<34weeks	281 (10.1)	7 (5.6)	0.096	0.53 (0.24-1.14)	0.116	0.88 (0.76-1.03)
Delivery<37weeks	1240 (44.5)	21 (16.7)	<0.001	0.25 (0.16-0.40)	<0.001	0.76 (0.69-0.83)
Pregnancy loss <24weeks	182 (6.5)	6 (4.8)	0.430	0.72 (0.31-1.65)	0.400	0.93 (0.79-1.10)
All surviving	2188(78.5)	120 (95.2)	<0.001	5.48 (2.40-12.52)	<0.001	1.44(1.22-1.70)
Caesarean section	2401/2591 (92.7)	92/120 (76.7)	<0.001	0.26 (0.17-0.41)	<0.001	0.76 (0.69-0.83)
Birth weight (g)	2550 (2225-2850)	3080 (2750-3350)	<0.001	–	<0.001	–
At least one LBW	1311 (47.0)	17 (13.5)	<0.001	0.18 (0.11-0.30)	<0.001	0.71 (0.64-0.79)
At least one VLBW	106 (3.8)	4 (3.2)	0.903	0.83 (0.30-2.29)	0.703	0.96 (0.78-1.18)
At least one SGA	1103 (39.6)	17 (13.5)	<0.001	0.24 (0.14-0.40)	<0.001	0.75 (0.68-0.85)

Data are presented as median (IQR) or number (%). Mann–Whitney U tests and Chi-square tests or Fisher’s exact test were used for unadjusted analysis. Logistic regression and linear regression were used for adjusting certain confounders, including maternal age at conception, maternal BMI before pregnancy, type of infertility, ART methods, embryo transplantation, source of semen.

GA, gestational age; LBW, low birth weight; VLBW, very low birth weight; SGA, small for gestational age; OR, odds ratio; CI, confidence interval.