title: Second trimester cervical length and risk of preterm birth in women with twin gestations treated with 17-α hydroxyprogesterone caproate.
abstract: OBJECTIVE
  To compare rates of preterm birth before 35 weeks based on cervical length measurement at 16-20 weeks in women with twin gestations who received 17-α hydroxyprogesterone caproate (17OHPC) or placebo.
  
  
  METHODS
  This is a secondary analysis of a randomised, double-blind, placebo-controlled trial of twin gestations exposed to 17OHPC or placebo. Baseline transvaginal ultrasound evaluation of cervical length was performed prior to treatment assignment at 16-20 weeks. Cervical length measurements were categorised according to the 10th, 25th, 50th and 75th percentiles in the women studied. The effect of 17OHPC administration in women with a short (25th percentile) and long (75th percentile) cervix was evaluated.
  
  
  RESULTS
  Of 661 twin gestations studied, 221 (33.4%) women enrolled at 11 centers underwent cervical length measurement. The 10th, 25th, 50th, 75th percentiles for cervical length at 16-20 weeks were 32, 36, 40 and 44 mm, respectively. The risk of preterm birth <35 weeks was increased in women with a cervical length <25th percentile (55.8 vs. 36.9%, p=0.02). However, a cervical length >75th percentile at this gestational age interval was not protective for preterm birth (36.5 vs. 42.9%, p=0.42). Administration of 17OHPC did not reduce preterm birth before 35 weeks among those with either a short or a long cervix (64.3 vs. 45.8%, p=0.18 and 38.1 vs. 35.5%, p=0.85, respectively).
  
  
  CONCLUSIONS
  Women with twin gestations and a cervical length below the 25th percentile at 16-20 weeks had higher rates of preterm birth. In this subgroup of women, 17 OHPC did not prevent preterm birth before 35 weeks gestation. A cervical length above the 75th percentile at 16-20 weeks did not significantly reduce the risk of preterm birth in this high risk population.
authors.affiliation: Department of Obstetrics and Gynecology, The Ohio State University, Columbus, OH 43210, USA. celeste.durnwald@osumc.edu
authors.forename: Celeste P
authors.initials: CP
authors.lastname: Durnwald
authors.forename: Valerija
authors.initials: V
authors.lastname: Momirova
authors.forename: Dwight J
authors.initials: DJ
authors.lastname: Rouse
authors.forename: Steve N
authors.initials: SN
authors.lastname: Caritis
authors.forename: Alan M
authors.initials: AM
authors.lastname: Peaceman
authors.forename: Anthony
authors.initials: A
authors.lastname: Sciscione
authors.forename: Michael W
authors.initials: MW
authors.lastname: Varner
authors.forename: Fergal D
authors.initials: FD
authors.lastname: Malone
authors.forename: Brian M
authors.initials: BM
authors.lastname: Mercer
authors.forename: John M
authors.initials: JM
authors.lastname: Thorp
authors.forename: Yoram
authors.initials: Y
authors.lastname: Sorokin
authors.forename: Marshall W
authors.initials: MW
authors.lastname: Carpenter
authors.forename: Julie
authors.initials: J
authors.lastname: Lo
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ramin
authors.forename: Margaret
authors.initials: M
authors.lastname: Harper
authors.forename: Catherine Y
authors.initials: CY
authors.lastname: Spong
mesh_terms: D000077713:17 alpha-Hydroxyprogesterone Caproate; D000328:Adult; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D004311:Double-Blind Method; D005260:Female; D005865:Gestational Age; D006801:Humans; D006908:Hydroxyprogesterones / Q000008:administration & dosage*; D010919:Placebos; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D047928:Premature Birth / Q000000981:diagnostic imaging / Q000517:prevention & control*; D012307:Risk Factors; D014427:Twins; D014463:Ultrasonography
chemical_list: D006908:Hydroxyprogesterones; D010919:Placebos; D000077713:17 alpha-Hydroxyprogesterone Caproate