Table 1.
Discriminative ability of shortest endocervical length (distance A–B) measured at 18+0–20+6 weeks of gestation (C×1, n = 11 072) with regard to predicting spontaneous preterm birth, including late spontaneous miscarriage
| sPTB | No. sPTB (%) |
AUC [95% CI] |
Cervical length | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0–15 mm (n = 15; 0.14%) | 0–20 mm (n = 67; 0.6%) | 0–25 mm (n = 441; 4.0%) | Best cut‐off* | ||||||||||||
|
Sensitivity [95% CI] |
Specificity [95% CI] |
FP/TP; NNS |
Sensitivity [95% CI] |
Specificity [95% CI] |
FP/TP; NNS |
Sensitivity [95% CI] |
Specificity [95% CI] |
FP/TP; NNS |
Sensitivity [95% CI] |
Specificity [95% CI] |
FP/TP; NNS |
mm | |||
| <28 GW |
22 (0.20%) |
0.83 [0.74–0.92] |
3/22 (13.6%] [2.9–34.9] |
11 038/11 050 (99.9%) [99.8–99.9] |
4; 3691 |
4/22 (18.2) [5.2–40.3] |
10 987/11 050 (99.4%) [99.3–99.6] |
16; 2768 |
9/22 (40.9%) [20.7–63.7] |
10 618/11 050 (96.1%) [95.7–96.4] |
48; 1230 |
18/22 (81.8%) [59.7–94.8] |
7685/11 050 (69.5%) [68.7–70.4] |
187; 615 |
32 (n = 3383; 30.6%) |
| <29 GW |
24 (0.22%) |
0.84 [0.76–0.92] |
3/24 (12.5%) [2.7–32.4] |
11 036/11 048 (99.9%) [99.8–99.9] |
4; 3691 |
5/24 (20.8%) [7.1–42.2] |
10 986/11 048 (99.4%) [99.3–99.6] |
12; 2214 |
10/24 (41.7%) [22.1–63.4] |
10 617/11 048 (96.1%) [95.7–96.5] |
43; 1107 |
20/24 (83.3%) [62.6–95.3] |
7685/11 048 (69.6%) [68.7–70.4] |
168; 554 |
32 (n = 3383; 30.6%) |
| <30 GW |
34 (0.31%) |
0.77 [0.68–0.87] |
3/34 (8.8%) [1.9–23.7] |
11 026/11 038 (99.9%) [99.8–99.9] |
4; 3691 |
5/34 (14.7%) [5.0–31.1] |
10 976/11 038 (99.4%) [99.3–99.6] |
12; 2214 |
12/34 (35.3%) [19.8–53.5] |
10 609/11 038 (96.1%) [95.7–96.5] |
36; 923 |
25/34 (73.5%) [55.6–87.1] |
7680/11 038 (69.6%) [68.7–70.4] |
134; 443 |
32 (n = 3383; 30.6%) |
| <31 GW |
40 (0.36%) |
0.76 [0.67–0.85] |
3/40 (7.5%) [1.6–20.4] |
11 020/11 032 (99.9%) [99.8–99.9] |
4; 3691 |
6/40 (15.0%) [5.7–29.8] |
10 971/11 032 (99.4%) [99.3–99.6] |
10; 1845 |
13/40 (32.5%) [18.6–49.1] |
10 604/11 032 (96.1%) [95.7–96.5] |
33; 852 |
29/40 (72.5%) [56.1–85.4] |
7678/11 032 (69.6%) [68.7–70.5] |
116; 382 |
32 (n = 3383; 30.6%) |
| <32 GW |
46 (0.42%) |
0.71 [0.62–0.80] |
3/46 (6.5%) [1.4–17.9] |
11 014/11 026 (99.9%) [99.8–99.9] |
4; 3691 |
6/46 (13.0%) [4.9–26.3] |
10 965/11 026 (99.4%) [99.3–99.6] |
10; 1845 |
14/46 (30.4%) [17.7–45.8] |
10 599/11 026 (96.1%) [95.8–96.5] |
31; 791 |
23/46 (50.0%) [34.9–65.1] |
9411/11 026 (85.4%) [84.7–86.0] |
70; 481 |
29 (n = 1638; 14.8%) |
| <33 GW |
63 (0.57%) |
0.68 [0.60–0.76] |
3/63 (4.8%) [1.0–13.3] |
10 997/11 009 (99.9%) [99.8–99.9] |
4; 3691 |
7/63 (11.1%) [4.6–21.6] |
10 949/11 009 (99.5%) [99.3–99.6] |
9; 1582 |
17/63 (27.0%) [16.6–39.7] |
10 585/11 009 (96.1%) [95.8–96.5] |
25; 651 |
27/63 (42.9%) [30.5–56.0] |
9398/11 009 (85.4%) [84.7–86.0] |
60; 410 |
29 (n = 1638; 14.8%) |
| <33 GW** | 56 (0.51%**) |
0.66 [0.58–0.74] |
1/56 (1.8%) [0.1–9.6] |
10 996/11 008 (99.9%) [99.8–99.9] |
12; 11 064 |
5/56 (8.9%) [8.9–19.6] |
10 948/11 008 (99.5%) [99.3–99.6] |
12; 2213 |
13/56 (23.2%) [13.0–36.4] |
10 584/11 008 (96.1%) [95.8–96.5] |
33; 851 |
38/56 (67.9%) [54.0–79.7] |
6364/11 008 (57.8%) [56.9–58.7] |
122; 291 |
34 (n = 4682; 42.3%) |
| <34 GW |
94 (0.85%) |
0.65 [0.59–0.72] |
3/94 (3.2%) [0.7–9.0] |
10 966/10 978 (99.9%) [99.8–99.9] |
4; 3691 |
7/94 (7.4%) [3.1–14.7] |
10 918/10 978 (99.5%) [99.3–99.6] |
9; 1582 |
20/94 (21.3%) [13.5–30.9] |
10 557/10 978 (96.2%) [95.8–96.5] |
21; 554 |
35/94 (37.2%) [27.5–47.8] |
9375/10 978 (85.4%) [84.7–86.1] |
46; 316 |
29 (n = 1638; 14.8%) |
| <35 GW | 143 (1.29%) |
0.62 [0.57–0.67] |
4/143 (2.8%) [0.8–7.0] |
10 918/10 929 (99.9%) [99.8–100.0] |
3; 2768 |
8/143 (5.6%) [2.5–10.7] |
10 870/10 929 (99.5%) [99.3–99.6] |
7; 1384 |
22/143 (15.4%) [9.9–22.4] |
10 510/10 929 (96.2%) [95.8–96.5] |
19; 503 |
69/143 (48.3%) [39.8–56.8] |
7615/10 929 (69.7%] [68.8–70.5] |
48; 161 |
32 (n = 3383; 30.6%) |
| <36 GW | 226 (2.04%) |
0.61 [0.57–0.65] |
4/226 (1.8%) [0.5–4.5] |
10 835/10 846 (99.9%) [99.8–100.0] |
3; 2768 |
9/226 (4.0%) [1.8–7.4] |
10 788/10 846 (99.5%) [99.3–99.6] |
6; 1230 |
30/226 (13.3%) [9.1–18.4] |
10 435/10 846 (96.2%) [95.8–96.6] |
14; 369 |
118/226 (52.2%) [45.5–58.9] |
6951/10 846 (64.1%) [63.2–65.0] |
33; 94 |
33 (n = 4013–36.2%) |
| <37 GW | 417 (3.77%) |
0.60 [0.57–0.63] |
5/417 (1.2%) [0.4–2.8] |
10 645/10 655 (99.9%) [99.8–100.0] |
2; 2214 |
13/417 (3.1%) [1.7–5.3] |
10 601/10 655 (99.5%) [99.3–99.6] |
4; 852 |
38/417 (9.1%) [6.5–12.3] |
10 252/10 655 (96.2%) [95.8–96.6] |
11; 291 |
207/417 (49.6%) [44.7–54.6] |
6849/10 655 (64.3%) [63.4–65.2] |
18; 54 |
33 (n = 4013; 36.2%) |
Positive and negative predictive values and positive and negative likelihood ratios are shown in Table S8.
GW, gestational weeks; sPTB, spontaneous preterm birth including miscarriage; AUC, area under receiver operating characteristic curve; CI, confidence interval; FP, false positive; TP, true positive; NNS, number needed to screen, i.e. number of women needed to screen to detect one true positive test result.
Best cut‐off is the cut‐off associated with the largest number of correctly classified cases, calculated using Youden’s index. 21
Late miscarriage excluded, with n = 11 064 as denominator.