Predictive value of transvaginal ultrasound measurement of cervical length in first and second trimester on spontaneous preterm birth in singleton pregnancies / 中华围产医学杂志

ABSTRACT

Objective:To explore the predictive value of transvaginal ultrasound measurement of cervical length (CL) in the first and second trimester on spontaneous preterm birth in singleton pregnant women.Methods:This study retrospectively recruited 2 254 singleton pregnancies without severe comorbidities at Peking University First Hospital from January 2019 to June 2019. CL was measured for all subjects using transvaginal ultrasound in the first (11-13 +6 weeks) and second trimester (21-23 +6 weeks). Differences in CL between women with preterm (preterm group) and full-term delivery (full-term group) as well as the CL during the first and second trimester were compared. The independent risk factors for preterm birth and the predictive value of CL in the first and second trimester for spontaneous preterm birth were also explored. Fisher's exact test, t-test, χ2 test, and logistic regression analysis, etc, were adopted for statistical analysis. Results:(1) For the 2 254 subjects, CL measured in the first trimester and second trimester were (36.1±4.2) mm (22.4-52.6 mm) and (36.9±5.3) mm (2.9-59.7 mm), respectively. The incidence of short cervix in the first trimester and second trimester were 0.31% (7/2 254) and 1.46% (33/2 254), respectively. When CL was ≤25.0 mm ( OR=43.92, 95% CI6.83-282.49) or >25.0-≤30.3 mm ( OR=6.59, 95% CI1.97-22.0) in the first trimester, the risk of short cervix increased in the second trimester (both P<0.05). (2) The total incidence of preterm delivery was 3.06% (69/2 254). CL and the incidence of short cervix did not differ significantly in the first trimester between the preterm and full-term group [(35.2±4.5) and (36.1±4.1) mm, t=－1.78, P=0.076; 1.5% (1/69) and 0.3% (6/2 185), χ 2=2.98, P=0.084]. Compared with the full-term group, CL was shorter and the incidence of short cervix was higher in the second trimester in the preterm group [(33.6±6.7) vs (37.0±5.2) mm, t=－5.12;8.7% (6/69) vs 1.2% (27/2 185), χ 2=25.80, P<0.001]. (3) Multivariate regression analysis showed that age ≥35 years ( OR=2.05, 95% CI1.22-3.46), history of spontaneous preterm birth ( OR=25.25, 95% CI5.01-127.28), conception assisted by reproductive technology ( OR=10.39, 95% CI2.39-50.33), and short cervix during the second trimester were independent risk factors for premature delivery. (4) There was no significant difference in the risk of preterm delivery when comparing to those with CL≤25.0 mm, >25.0-≤30.3 mm, >30.3-≤33.0 mm, >33.0-≤35.7 mm, >35.7-≤38.7 mm women with CL>38.7 mm during the first trimester (all P>0.05). The risk of premature delivery was relatively increased for those with CL≤25.0 mm,>25.0-≤29.5 mm, >29.5-≤33.6 mm, >33.6~≤36.8 mm, >36.8~≤40.1 mm during the second trimester compared to those with CL>40.1 mm [ OR (95% CI)17.64 (4.99-62.32), 6.89 (2.11-22.55), 3.58 (1.34-9.59), 4.04 (1.58-10.32), 3.34 (1.28-8.67), respectively , all P<0.05]. (5) When CL≤25.0 mm and ≤29.5 mm in the second trimester were used as the cut-off value, the prediction of preterm delivery was with a sensitivity of 8.70% and 17.39%, specificity of 98.80% and 95.29%, positive predictive value of 18.20% and 10.43%, negative predictive value of 97.16% and 97.34%, and the accuracy rate of 96.01% and 92.90%, respectively. Conclusions:There were no significant differences in CL and the incidence of short cervix during the first trimester among women with preterm or full-term delivery. CL in the first trimester is not an independent risk factor for preterm birth, but the risk of short cervix in the second trimester is increased when CL≤30.3 mm in the first trimester. The shorter the cervix during the second trimester, the greater the risk of preterm birth.