title: Transvaginal ultrasonographic measurement of cervical length in asymptomatic high-risk women with a short cervical length in the previous pregnancy.
abstract: OBJECTIVE
  To determine if asymptomatic women at high risk of preterm delivery who had a short cervical length in their previous pregnancy and delivered at term are at increased risk of having a short cervical length in their next pregnancy, and whether they are at increased risk of preterm birth.
  
  
  METHODS
  This retrospective cohort study included high-risk (those with a history of spontaneous preterm birth, uterine anomaly or excisional treatment for cervical dysplasia) asymptomatic women who were pregnant with a singleton gestation delivering between April 2003 and March 2010, who had had a previous pregnancy and who had transvaginal ultrasonographic cervical length measurement performed at 16-30 weeks' gestation in both pregnancies. Comparison was among women who had a short cervical length (< 3.0 cm) in their previous pregnancy but delivered at term in that pregnancy (Short Term Group), women with a history of a normal cervical length (≥ 3.0 cm) in their previous pregnancy delivering at term (Long Term Group), and women who had a short cervical length (< 3.0 cm) in their previous pregnancy delivering preterm (Short Preterm Group). Primary outcomes were spontaneous preterm birth at < 37 weeks' gestation and cervical length. Secondary outcomes were spontaneous preterm birth at < 35 weeks and < 32 weeks, low birth weight, maternal outcomes and neonatal morbidity.
  
  
  RESULTS
  A total of 62 women were included. Women in the Short Term Group were more likely to have a short cervical length in their next pregnancy compared with those in the Long Term Group (10/23 (43.5%) vs. 4/26 (15.4%), respectively) but not as likely as women in the Short Preterm Group (9/13 (69.2%); P=0.003). Women in the Short Term Group were not at an increased risk of spontaneous preterm birth at < 37 weeks in the next pregnancy compared with women in the Long Term Group (2/23 (8.7%) vs. 2/26 (7.7%), respectively), but women in the Short Preterm Group were at an increased risk (6/13 (46.2%); P<0.0001). Compared with women in the Short Term and Long Term groups, women in the Short Preterm Group were also at an increased risk of threatened preterm labor (6/23 (26.1%) and 4/26 (15.4%) vs. 9/13 (69.2%), respectively; P=0.002) and of receiving corticosteroids for fetal lung maturation (6/23 (26.1%) and 4/26 (15.4%) vs. 11/13 (84.6%), respectively; P<0.0001).
  
  
  CONCLUSIONS
  Although high-risk asymptomatic women with a short cervical length in their previous pregnancy who delivered at term are at increased risk of having a short cervix in their next pregnancy, they are not at increased risk of preterm birth.
authors.affiliation: Department of Obstetrics and Gynecology, Eastern Health, Memorial University, St. John's, Newfoundland, Canada. joan.crane@easternhealth.ca
authors.forename: J M G
authors.initials: JM
authors.lastname: Crane
authors.forename: D
authors.initials: D
authors.lastname: Hutchens
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement / Q000379:methods*; D002584:Cervix Uteri / Q000002:abnormalities / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D005260:Female; D020073:Gravidity; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D047928:Premature Birth / Q000000981:diagnostic imaging* / Q000517:prevention & control; D011336:Probability; D012189:Retrospective Studies; D012307:Risk Factors; D014621:Vagina / Q000000981:diagnostic imaging