Cervical length measurement at mid-gestation to predict spontaneous preterm birth in triplet pregnancies

Objectives
The aim of this study was to evaluate the predictive value of cervical length (CL) for spontaneous preterm birth (PTB) in triplet pregnancies.
Methods
This was a retrospective study on triplet pregnancies followed at five Italian Centres between 2002 and 2015. Cervical length was measured transvaginally between 18–24 weeks gestation. CL predictive values for PTB <28, <30 and <32 weeks gestation were assessed. Distributions of CL measurements in patients with PTB were calculated. Logistic regression analysis was performed to assess the association between pregnancy characteristics and PTB.
Results
120 patients were included. Median CL was 35 mm (IQR 29–40): 17 (14.2%) and 8 (6.7%) patients had a CL <20 and <15 mm respectively, measured at a median gestational age of 20+2 (IQR 20+0-23+4) weeks. Spontaneous PTB < 32 weeks occurred in 41 (34.2%), < 30 weeks in 23 (19.2%) and < 28 weeks in 12 (10%) cases. A cervix < 15 mm was significantly more frequent in the group of patients delivered < 28 and < 30 weeks (p = 0.03, p = 0.01), while a cervical length < 20 mm was more common in triplet pregnancies delivered < 32 weeks (p = 0.03). The distribution of cervical length in triplet pregnancies complicated with PTD is reported in figure 1. Logistic regression analysis was possible for PTB < 32 weeks: after adjustment for confounders CL was not associated to PTB (OR 0.97, CI 0.94-1.01). CL showed an AUC 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 PTB < 28, < 30 and < 32 weeks.
Conclusions
CL assessed at mid gestation is a poor predictor of PTB in asymptomatic triplet pregnancies.