Table 2.

Spontaneous preterm birth and preterm PROM prior to 37, 35 and 32 weeks’ gestation.^*

Outcome	Vitamins N=4,992	Placebo N=4,976	OR [95% CI]	Adjusted OR# [95% CI]
SPB < 37 weeks	356 (7.1)	342 (6.9)	1.04 [0.89, 1.21]	1.05 [0.90, 1.22]
SPB < 35 weeks	177 (3.6)	185 (3.7)	0.95 [0.77, 1.17]	0.96 [0.77, 1.18]
SPB < 32 weeks	109 (2.2)	124 (2.5)	0.87 [0.67, 1.13]	0.88 [0.67, 1.14]
SPB due to preterm PROM <37 weeks	124 (2.5)	129 (2.6)	0.96 [0.75, 1.23]	0.96 [0.75, 1.23]
SPB due to preterm PROM <35 weeks	56 (1.1)	58 (1.2)	0.96 [0.66, 1.39]	0.97 [0.67, 1.40]
SPB due to preterm PROM <32 weeks	15 (0.3)	30 (0.6)	0.50 [0.27, 0.92]	0.50 [0.27, 0.93]
Preterm PROM <37 weeks	130 (2.6)	132 (2.7)	0.98 [0.77, 1.25]	0.98 [0.77, 1.26]
Preterm PROM <35 weeks	58 (1.2)	61 (1.2)	0.95 [0.66, 1.36]	0.95 [0.66, 1.37]
Preterm PROM <32 weeks	18 (0.4)	32 (0.6)	0.56 [0.31, 1.00]	0.56 [0.32, 1.00]

^*Presented as number (%). SPB total spontaneous preterm births (preterm PROM or preterm labor), preterm PROM preterm premature rupture of membranes.

^#Adjusted for race, smoking, baseline body mass index and center.