Table 4.

A priori subgroup analyses for preterm birth prior to 37 weeks^*

	17-OHP (N = 327)	Placebo (N = 330)	RR (95% CI)	P**
Gestational age at randomization				0.20
< 21 weeks	21/104 (20.2)	26/101 (25.7)	0.78 (0.47 – 1.30)
≥21 weeks	61/223 (27.4)	54/229 (23.6)	1.16 (0.85 – 1.59)
Cervical length				0.70
< 15 mm	13/25 (52.0)	17/ 31(54.8)	0.95 (0.58 – 1.55)
≥15 mm	69/302 (22.8)	63/299 (21.1)	1.08 (0.80 – 1.47)
Cervical funnel				0.08
Absent	54/239 (22.6)	50/261 (19.2)	1.18 (0.84 – 1.66)
Present	28/88 (31.8)	30/69 (43.5)	0.73 (0.49 – 1.10)

^*Data presented as n/N (%)

^**P value for Breslow-Day interaction term