title: Prediction of preterm birth by second trimester cervical sonography in twin pregnancies.
abstract: OBJECTIVE
  To determine the predictive value of sonographic cervical length and of funneling for spontaneous preterm delivery (PTD) in twin pregnancies under 26 weeks' gestation.
  
  
  METHODS
  Women with twin pregnancies were studied prospectively with transvaginal or translabial ultrasound of the cervix from 18 to 26 weeks' gestation. Exclusion criteria were: signs of preterm labor, prophylactic cervical cerclage, placenta previa, or severe congenital fetal anomaly. The primary outcome was spontaneous preterm birth at < 35 weeks' gestation.
  
  
  RESULTS
  Sixty-five twin pregnancies were analyzed, of which 23% (15/65) delivered preterm. Cervical ultrasound examination was performed by 22 weeks' gestation in 75% and by 24 weeks' gestation in 91% of women. Cervical length < or = 25 mm and < or = 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 funneling, 70% delivered preterm, all under 32 weeks' gestation. By logistic regression analysis, both short cervix < or = 30 mm and any funneling were strongly predictive of PTD.
  
  
  CONCLUSIONS
  Both cervical length < or = 30 mm and cervical funneling in twin pregnancies under 26 weeks' gestation are independently and strongly associated with high risk for preterm birth. A long cervix, of length > 35 mm, is associated with very low risk (4%) for preterm birth.
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Cheil Hospital, Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Yang
authors.forename: K
authors.initials: K
authors.lastname: Kuhlman
authors.forename: S
authors.initials: S
authors.lastname: Daly
authors.forename: V
authors.initials: V
authors.lastname: Berghella
mesh_terms: D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007752:Obstetric Labor, Premature; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D011272:Pregnancy, Multiple; D011446:Prospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D014427:Twins; D016216:Ultrasonography, Prenatal