Serial versus Once-Only Cervical Length Screening in Twin Pregnancies.

OBJECTIVE

To assess the impact of serial versus once-only transvaginal ultrasound (TVU) cervical length (CL) screening in twin pregnancies.

STUDY

DESIGN

Multicenter retrospective cohort study including twin pregnancies who underwent TVU CL screening from 160/7 to 236/7 weeks of gestation between 2017 and 2022. Twin pregnancies resulting from multifetal pregnancy reduction after 14 weeks of gestation, monochorionic monoamniotic twins, and those undergoing a history-indicated cerclage were excluded. Cases were stratified into two groups based on number of TVU CL assessments: twins who had more than one CL assessment from 160/7 to 236/7 weeks' gestation (i.e., serial CL group) versus twins who had only one CL assessment at the time of their detailed fetal anatomy ultrasound from 180/7 to 216/7 weeks' gestation (i.e., once-only CL group). Sensitivity, specificity, positive predictive value, and negative predictive value of CL screening for predicting preterm birth (PTB) at various gestational age cutoffs (<34, <32, and <28 weeks of gestation) were calculated using thresholds of both ≤25 and ≤30 mm and compared between the two groups. Statistical significance was set at p < 0.05.

RESULTS

Of the 1,917 patients included, 962 (50.2%) were in the serial CL group and 955 (49.8%) were in the once-only CL group. The incidence of a short CL ≤ 25 mm was significantly higher in the serial CL group compared with the once-only CL group (12.6 vs. 0.9%, p <0.001). The sensitivity of CL screening for predicting PTB, when using a threshold of ≤25 mm, was higher in the serial CL group compared with the once-only CL group for each PTB cut-off (<34 weeks: 27.9 vs. 4.2%; <32 weeks: 40.7 vs. 7.4%; <28 weeks: 47.2 vs. 11.8%, respectively).

CONCLUSION

Serial TVU CL screening from 160/7 to 236/7 weeks of gestation should be considered in twin pregnancies.

KEY POINTS: · Serial CL screening increased the detection of a short cervix compared with once-only screening.. · Serial CL screening improved sensitivity for predicting PTB compared with once-only screening.. · Serial transvaginal CL screening from 16 to 236/7 weeks should be considered in twin pregnancies..