Prediction of preterm birth by second trimester cervical sonography in twin pregnancies

Objectives To determine the predictive value of sonographic cervical length and of funneling for spontaneous preterm delivery (PTD) in twin pregnancie s tinder 26 weeks' gestation Methods Women with twin pregnancies were studied prospectively with transva ginal or translabial ultrasound of the cervix from 18 to 26 weeks' gestatio n. Exclusion criteria were: signs of preterm labor, prophylactic cervical c erclage, placenta previa, ou severe congenital fetal anomaly The primary ou tcome was spontaneous preterm birth at < 35 weeks' gestation. Results Sixty-five twin pregnancies were analyzed of which 23% (15/65) deli vered preterm. Cervical ultrasound examination was performed by 22 weeks' g estation in 75% and by 24 weeks' gestation in 91% of women. Cervical length less than or equal to 75 mm and less than or equal to 30 mm was associated with sensitivities of 27% and 53%, respectively and with 67% and 62% rates of PTD, respectively (R.R. 4.6, C.I. 2.0-10.3 and R.R. 3.6, C.I. 1.6-7.8, respectively). A cervical length >35 mm was associated with only a 4% rate of PTD (R.R 0.13; C.I. 0.02-0.93). Of 10 women (15%) with any cervical funn eling, 70% delivered preterm, all under 32 weeks' gestation. By logistic re gression analysis, both short cervix less than or equal to 30 mm and any fu nneling were strongly predictive of PTD. Conclusions Both cervical length less than or equal to 30 mm and cervical f unneling in twin pregnancies under 26 weeks' gestation ave independently an d strongly associated with high risk tr preterm birth. A long cervix, of le ngth > 35 mm, is associated with very low risk (4%) for preterm birth.