TABLE 2.

Pooled estimates for changes in cervical length over time to predict preterm birth

Population	Outcome	Abnormal test result	No. of studies/ total number of women	Sensitivity (%) (95% CI)	Specificity (%) (95% CI)	Positive likelihood ratio (95% CI)	Negative likelihood ratio (95% CI)	I2 (%)
Singleton gestation (all)	Preterm birth <37 wk	Any shortening of CL	448–50,53/532	54 (43–65)	84 (80–87)	3.2 (2.2–4.4)	0.6 (0.4–0.9)	0
	Preterm birth <35 wk	Any shortening of CL	54,44,47,49,53/2979	65 (57–72)	48 (46–50)	1.3 (1.1–1.4)	0.7 (0.6–0.9)	25
Singleton gestation at high risk	Preterm birth <37 wk	Any shortening of CL	348,49,53/275	49 (37–61)	85 (80–90)	3.3 (2.2–5.0)	0.6 (0.5–0.8)	0
	Preterm birth <35 wk	Any shortening of CL	444,47,49,53/448	58 (47–68)	72 (67–76)	2.0 (1.6–2.6)	0.6 (0.4–0.8)	12
Singleton gestation at high risk with an initial normal CL	Preterm birth <35 wk	Shortening of CL to <25 or <30 mm at ≤24 wks	244,47/310	56 (43–68)	72 (66–77)	2.0 (1.5–2.7)	0.6 (0.4–0.8)	63
Singleton gestation (unselected)	Preterm birth <35 wk	Any decrease in CL	14/2531	72 (62–81)	44 (42–46)	1.3 (1.1–1.5)	0.6 (0.4–0.9)	NA
Singleton gestation at low risk	Preterm birth <37 wk	Shortening of CL ≥6.6 mm	150/257	74 (51–88)	82 (77–86)	4.1 (2.8–6.0)	0.3 (0.1–0.7)	NA
Twin gestation	Preterm birth <34 wk	Any shortening of CL	745,46,51,52,54–56 /852	47 (39–55)	88 (86–91)	4.0 (2.0–8.3)	0.6 (0.5–0.8)	66
		Shortening of CL ≥20- 25%	545,51,54–56 /651	47 (38–57)	87 (84–90)	3.8 (2.8–5.1)	0.6 (0.5–0.7)	76
	Preterm birth <32 wk	Any shortening of CL	451,52,54,55 /644	61 (49–73)	88 (85–91)	5.3 (3.4–7.2)	0.5 (0.3–0.6)	0
		Shortening of CL ≥20- 25%	351,54,55/520	56 (42–69)	89 (86–92)	5.2 (3.7–7.5)	0.5 (0.4–0.7)	0
	Preterm birth <30 wk	Any shortening of CL	351,52,55 /454	70 (52–83)	86 (82–89)	4.8 (3.5–6.8)	0.4 (0.2–0.6)	0
	Preterm birth <28 wk	Any shortening of CL	351,52,55/454	73 (48–89)	84 (80–88)	4.5 (3.1–6.6)	0.3 (0.2–0.7)	0

CI, confidence interval; CL, cervical length; NA, not applicable