title: A Longitudinal Study of Changes in Prenatal Care Utilization Between First and Second Births and Low Birth Weight.
abstract: OBJECTIVE
  Because previous analyses of prenatal care (PNC) utilization and risk of low birth weight (LBW) may have been influenced by selection bias, we conducted a study using longitudinal data of women with repeat pregnancies.
  
  
  METHODS
  We analyzed Washington State birth certificates of first and second live births (2003-2012). We estimated relative risk (RR) of LBW at second birth associated with Kotelchuck Index PNC level among women stratified by level of PNC in their first birth (n = 67,571).
  
  
  RESULTS
  Among women with inadequate PNC prior to their first birth (n = 10,355), women with intermediate or adequate PNC before their second birth (n = 7464) had a reduced risk of LBW (adjusted RR 0.61, 95% CI: 0.48, 0.78) compared to those whose PNC level remained inadequate. Likewise, among women with intermediate or adequate PNC prior to their first birth (n = 57,216), those with inadequate PNC before the second birth (n = 7095) had higher risk of LBW (adjusted RR 1.59, 95% CI: 1.36, 1.85) compared to those who remained at intermediate or adequate PNC.
  
  
  CONCLUSIONS
  Our findings support the hypothesis that PNC decreases LBW risk at second birth, independent of factors related to the utilization of PNC at first birth.
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA, 98195, USA.
authors.forename: Christine T
authors.initials: CT
authors.lastname: Loftus
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA, 98195, USA. orions@uw.edu.
authors.forename: Orion T
authors.initials: OT
authors.lastname: Stewart
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA, 98195, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hensley
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA, 98195, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Enquobahrie
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA, 98195, USA.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Hawes
mesh_terms: D005260:Female; D020073:Gravidity; D006801:Humans; D007230:Infant, Low Birth Weight; D008137:Longitudinal Studies; D011247:Pregnancy; D011295:Prenatal Care / Q000706:statistics & numerical data*; D012307:Risk Factors
keywords: Epidemiology; Low birth weight; Pregnancy; Prenatal care; Selection bias