title: Relationship among placenta previa, fetal growth restriction, and preterm delivery: a population-based study.
abstract: OBJECTIVE
  To examine the independent contributions of prematurity and fetal growth restriction to low birth weight among women with placenta previa.
  
  
  METHODS
  A population-based, retrospective cohort study of singleton live births in New Jersey (1989-93) was performed. Mother-infant pairs (n = 544,734) were identified from linked birth certificate and maternal and infant hospital discharge summary data. Women diagnosed with previa were included only if they were delivered by cesarean. Fetal growth, defined as gestational age-specific observed-to-expected mean birth weight, and preterm delivery (before 37 completed weeks) were examined in relation to previa. Severe and moderate categories of fetal smallness and large for gestational age were defined as observed-to-expected birth weight ratios below 0.75, 0.75-0.85, and over 1.15, respectively, all of which were compared with appropriately grown infants (observed-to-expected birth weight ratio 0.86-1.15).
  
  
  RESULTS
  Placenta previa was recorded in 5.0 per 1000 pregnancies (n = 2744). After controlling for maternal age, education, parity, smoking, alcohol and illicit drug use, adequacy of prenatal care, maternal race, as well as obstetric complications, previa was associated with severe (odds ratio [OR] 1.37, 95% confidence interval [CI] 1.25, 1.50) and moderate fetal smallness (OR 1.24, 95% CI 1.17, 1.32) births. Preterm delivery was also more common among women with previa. Adjusted OR of delivery between 20-23 weeks was 1.81 (95% CI 1.24, 2.63), and 2.90 (95% CI 2.46, 3.42) for delivery between 24-27 weeks. OR for delivery by each week between 28 and 36 weeks ranged between 2.7 and 4.0. Approximately 12% of preterm delivery and 3.7% of growth restriction were attributable to placenta previa.
  
  
  CONCLUSIONS
  The association between low birth weight and placenta previa is chiefly due to preterm delivery and to a lesser extent with fetal growth restriction. The risk of fetal smallness is increased slightly among women with previa, but this association may be of little clinical significance.
authors.affiliation: Section of Epidemiology and Biostatistics and the University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, New Jersey 08901-1977, USA.
authors.forename: C V
authors.initials: CV
authors.lastname: Ananth
authors.forename: K
authors.initials: K
authors.lastname: Demissie
authors.forename: J C
authors.initials: JC
authors.lastname: Smulian
authors.forename: A M
authors.initials: AM
authors.lastname: Vintzileos
mesh_terms: D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000209:etiology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D007752:Obstetric Labor, Premature / Q000209:etiology*; D016017:Odds Ratio; D010923:Placenta Previa / Q000150:complications*; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors