title: The epidemiology of threatened preterm labor: a prospective cohort study.
abstract: OBJECTIVE
  The purpose of this study was to describe the occurrence, timing, and outcomes of hospital-based diagnoses of preterm labor.
  
  
  METHODS
  Administrative records identified hospital admissions for preterm labor among 2534 women in an ongoing cohort study. Factors that were considered risks for prematurity were examined by logistic regression for an association with any preterm labor diagnosis, a preterm labor diagnosis <33 weeks of gestation, or > or =33 weeks of gestation.
  
  
  RESULTS
  Of 234 women (9%) who experienced hospitalization for preterm labor, 90 women (38%) were delivered in the first episode. Previous preterm birth consistently was associated with a diagnosis of preterm labor. Reporting a sexually transmitted infection (odds ratio, 1.8; 95% CI, 1.1-3.0) or bacterial vaginosis (odds ratio, 2.6; 95% CI, 1.7-4.1) early in pregnancy was associated with hospitalization for preterm labor between 24 and 32 weeks of gestation.
  
  
  CONCLUSIONS
  The incidence of first-time hospitalization for preterm labor was 9%, with most episodes not resulting in preterm birth. Previous preterm birth was associated therefore with a preterm labor diagnosis.
authors.affiliation: Departments of Obstetrics and Gynecology, Epidemiology, and Medicine, The University of North Carolina at Chapel Hill, NC 27599, USA. Auv7@cdc.gov
authors.forename: Melissa L
authors.initials: ML
authors.lastname: McPheeters
authors.forename: William C
authors.initials: WC
authors.lastname: Miller
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Hartmann
authors.forename: David A
authors.initials: DA
authors.lastname: Savitz
authors.forename: Jay S
authors.initials: JS
authors.lastname: Kaufman
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Garrett
authors.forename: John M
authors.initials: JM
authors.lastname: Thorp
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000428:Alcohol Drinking / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D007752:Obstetric Labor, Premature / Q000453:epidemiology* / Q000209:etiology; D016017:Odds Ratio; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011256:Pregnancy Outcome; D018566:Pregnancy, High-Risk; D011296:Prenatal Diagnosis / Q000379:methods; D015995:Prevalence; D011446:Prospective Studies; D012042:Registries; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology