title: Serial cervical length determination in twin pregnancies reveals 4 distinct patterns with prognostic significance for preterm birth.
abstract: Women with a twin gestation are at increased risk for preterm birth (PTB), and sonographic cervical length (CL) is a powerful predictor for spontaneous PTB. Obstetricians frequently monitor CL in multiple gestations; yet, the optimal method to integrate and interpret the results of serial sonographic CL has not been determined.
  
  
  
  We sought to determine whether there are different patterns of cervical shortening in twin gestations, and whether such patterns are related to the risk of PTB.
  
  
  
  We conducted a retrospective study of all women with twins followed up in a single tertiary referral center during 2012 through 2014. All women underwent serial measurements of CL every 2-3 weeks starting from 14-18 weeks and until 28-32 weeks of gestation. Changes in CL were analyzed and classified into distinct patterns that were initially identified by visual inspection of all individual cases. Each pattern was then characterized by several parameters including information about when cervical shortening began, the rate of shortening, and whether a plateau was observed. Locally weighted regression mean profiles were generated to describe each pattern of CL over time. The association of these patterns with spontaneous PTB was determined. The specific characteristics of each pattern that further determined the risk of PTB were identified using multivariable logistic regression analysis.
  
  
  
  We studied 441 women who had a total of 2826 measurements of CL done. Overall, 4 main patterns of change in CL were identified: pattern I, stable cervix (n = 196); pattern II, early and rapid shortening (n = 18); pattern III, late shortening (n = 109); and pattern IV, early shortening with a plateau (n = 118). The rate of PTB at <34 weeks was lowest in cases of pattern I (11.7%), followed by pattern IV (14.4%) and pattern III (20.2%), and was highest for women with pattern II (44.4%) (P < .001). In cases with pattern III (late shortening), the most important factors affecting the risk of PTB were the shortening rate, the gestational age at the onset of cervical shortening, and the initial plateau of CL. In the case of pattern IV (early shortening with a plateau), it was only the new plateau at which cervical shortening stopped that was associated with the risk of PTB.
  
  
  
  Changes in sonographic CL over time in twin gestations can be classified into 4 patterns, each associated with a different risk of PTB.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada. Electronic address: nir.melamed@sunnybrook.ca.
authors.forename: Nir
authors.initials: N
authors.lastname: Melamed
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Alex
authors.initials: A
authors.lastname: Pittini
authors.affiliation: Department of Obstetrics and Gynecology, Rabin Medical Center, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Liran
authors.initials: L
authors.lastname: Hiersch
authors.affiliation: Department of Obstetrics and Gynecology, Rabin Medical Center, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Yariv
authors.initials: Y
authors.lastname: Yogev
authors.affiliation: Perinatology Research Branch, Program for Perinatal Research and Obstetrics, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, and Detroit, MI; Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, MI; Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI.
authors.forename: Steven S
authors.initials: SS
authors.lastname: Korzeniewski
authors.affiliation: Perinatology Research Branch, Program for Perinatal Research and Obstetrics, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, and Detroit, MI; Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI; Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI; Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI.
authors.forename: Roberto
authors.initials: R
authors.lastname: Romero
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jon
authors.initials: J
authors.lastname: Barrett
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement / Q000379:methods*; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D008297:Male; D011247:Pregnancy; D059285:Pregnancy, Twin; D047928:Premature Birth / Q000000981:diagnostic imaging*; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D014427:Twins; D016216:Ultrasonography, Prenatal
keywords: biomarker; cervical ripening; longitudinal study; prediction; pregnancy; prematurity; preterm labor; ultrasound