. Author manuscript; available in PMC: 2022 Aug 9.

Published in final edited form as: Am J Obstet Gynecol. 2020 Feb 3;223(1):42–65.e2. doi: 10.1016/j.ajog.2019.12.266

TABLE 3.

Subgroup analyses of effect of cervical pessary on spontaneous preterm birth <34 weeks in singleton gestations with a cervical length ≤25 mm

Subgroup	No of trials	Pessary	No pessary	Relative risk (95% CI)	I², %	Interaction P value
Concomitant use of vaginal progesterone						0.70
No	4^{160–162,164}	31/521 (6.0%)	67/518 (12.9%)	0.70 (0.23–2.14)	78
Yes	3^162–164	62/408 (15.2%)	67/417 (16.1%)	0.91 (0.47–1.76)	67
Obstetric history						0.24
No previous preterm birth	3^162,164,165	78/605 (12.9%)	72/591 (12.2%)	0.97 (0.54–1.76)	71
≥1 previous preterm birth	1¹⁶²	7/70 (10.0%)	16/84 (19.0%)	0.53 (0.23–1.20)	NA
Cervical length						0.68
≤10 mm	2^162,164	28/111 (25.2%)	25/83 (30.1%)	0.58 (0.10–3.23)	85
11–25 mm	2^162,164	38/504 (7.5%)	48/534 (9.0%)	0.84 (0.56–1.27)	0

Data are n/N.

CI, confidence interval; NA, not applicable.