Table III.

Subgroup analysis of live birth rate.

	Progesterone (N = 136)	Placebo (N = 133)
	n/N (%)	n/N (%)	RR	95% CI	P	P for interaction
No. of miscarriages
0	58/69 (84.1)	47/56 (83.9)	1	0.86–1.17	0.984
≥1	54/67 (80.6)	65/77 (84.4)	0.95	0.82–1.11	0.55	0.664
Infertility for current pregnancy
No	90/106 (84.9)	88/104 (84.6)	1	0.89–1.13	0.953
Yes	19/25 (76.0)	19/23 (82.6)	0.92	0.69–1.23	0.572	0.585
Maternal age
<40 years	107/131 (81.7)	108/127 (85.0)	0.96	0.86–1.07	0.469
≥40 years	5/5 (100.0)	4/6 (66.7)	1.5	0.83–2.72	0.181	0.13
Baseline progesterone level
<25 nmol/l	2/10 (20.0)	1/5 (20.0)	1	0.11–9.23	1
25–50 nmol/l	40/49 (81.6)	40/50 (80.0)	1.02	0.84–1.24	0.837	0.985
>50 nmol/l	68/74 (91.9)	66/73 (90.4)	1.02	0.92–1.12	0.753	0.988
Gestation at recruitment
<8 weeks	70/89 (78.7)	66/82 (80.5)	0.98	0.84–1.14	0.767
8–10 weeks	42/47 (89.4)	46/51 (90.2)	0.99	0.87–1.13	0.892	0.894