title: The relationship between first-trimester subchorionic hematoma, cervical length, and preterm birth.
abstract: OBJECTIVE
  The objective of the study was to evaluate the association between a sonographically diagnosed subchorionic hematoma (SCH) in the first trimester and subsequent midtrimester cervical length and preterm birth.
  
  
  METHODS
  In this cohort study, 512 women with an SCH on their first-trimester ultrasound were compared with 1024 women without a first-trimester SCH. All women underwent routine transvaginal cervical length measurement between 18 and 22 weeks. Women with multifetal gestation, cerclage, or a uterine anomaly were excluded. A multivariable linear regression was performed to assess the independent association of SCH with cervical length, and a logistic regression was done to determine whether the presence of SCH was associated with preterm birth independent of the cervical length.
  
  
  RESULTS
  In a univariable analysis, the presence of a SCH was significantly associated with a shorter mean cervical length as well as a cervical length less than the 10th percentile (4.27 cm vs 4.36 cm, P = .038; 1.9% vs 0.5%, P = .006, respectively). Preterm birth also was more common in women with an SCH (12.5% vs 7.3%, P = .001). Even after adjusting for potentially confounding factors, a significant negative association existed between the presence of an SCH and cervical length (centimeters) (linear regression coefficient, -0.08; 95% confidence interval, -0.17 to -0.005). In a multivariable regression, SCH remained associated with preterm birth, even with cervical length entered into the equation as a covariate (adjusted odds ratio, 1.58; 95% confidence interval, 1.09-2.32).
  
  
  CONCLUSIONS
  First-trimester SCH is associated with both a shorter cervical length and preterm birth. Our data suggest, however, that mechanisms other than cervical shortening may be involved in preterm birth among women with SCH.
authors.affiliation: Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL. Electronic address: anna.palatnik@northwestern.edu.
authors.forename: Anna
authors.initials: A
authors.lastname: Palatnik
authors.affiliation: Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL.
authors.forename: William A
authors.initials: WA
authors.lastname: Grobman
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D002584:Cervix Uteri / Q000000981:diagnostic imaging / Q000473:pathology*; D002823:Chorion / Q000473:pathology*; D005260:Female; D006406:Hematoma / Q000000981:diagnostic imaging; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D011247:Pregnancy; D011248:Pregnancy Complications / Q000000981:diagnostic imaging; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D047928:Premature Birth / Q000000981:diagnostic imaging / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors
keywords: cervical length; preterm birth; subchorionic hematoma