Cervical-length measurement in mid-gestation to predict spontaneous preterm birth in asymptomatic triplet pregnancy

To assess the predictive value of sonographic cervical-length (CL) measurement in mid-gestation for spontaneous preterm birth (PTB) in asymptomatic triplet pregnancy.This was a retrospective study of asymptomatic triplet pregnancies followed at five Italian tertiary referral centers, between 2002 and 2015. CL was measured transvaginally between 18 and 24 weeks' gestation. Pregnancies with medically indicated PTB were excluded. Demographic and pregnancy characteristics of pregnancies complicated by PTB were analyzed and the distributions of CL measurements in these patients were calculated. Logistic regression analysis was performed to assess the association between CL and PTB, adjusted for confounders. Performance of CL measurement in prediction of PTB 28, 30 and 32 weeks of gestation was assessed.A total of 120 triplet pregnancies were included in the final analysis. Median CL was 35 (interquartile range (IQR), 29-40) mm measured at a median gestational age of 20 + 2 (IQR, 20 + 0 to 23 + 4) weeks. Overall, 23 (19.2%), 17 (14.2%) and eight (6.7%) patients had a CL 25, 20 and 15 mm, respectively. Spontaneous PTB 32 weeks occurred in 41 (34.2%) cases, 30 weeks in 23 (19.2%) and 28 weeks in 12 (10%) cases. CL 15 mm was significantly more frequent in the group of patients who delivered 28 (P = 0.03) and 30 (P = 0.01) weeks' gestation, compared with those who delivered after 28 and after 30 weeks, respectively, while CL 20 mm was more common in triplet pregnancies with delivery 32 weeks compared with those delivered ≥ 32 weeks (P = 0.03). Logistic regression analysis was possible only for PTB 32 weeks due to the small number of cases that delivered 30 and 28 weeks. After adjustment for confounders, CL was not significantly associated with PTB 32 weeks (adjusted odds ratio, 0.97; 95% CI, 0.94-1.01). CL measurement had an area under the receiver-operating characteristics curve of 0.41 (95% CI, 0.20-0.62), 0.41 (95% CI, 0.26-0.56) and 0.42 (95% CI, 0.31-0.54) for the prediction of spontaneous PTB 28, 30 and 32 weeks, respectively.CL assessed in mid-gestation is a poor predictor of PTB 28, 30 and 32 weeks' gestation in asymptomatic triplet pregnancy. Copyright © 2017 ISUOG. Published by John WileySons Ltd.