title: Measuring dosage: a key factor when assessing the relationship between prenatal case management and birth outcomes.
abstract: To assess whether a measure of prenatal case management (PCM) dosage is more sensitive than a dichotomous PCM exposure measure when evaluating the effect of PCM on low birthweight (LBW) and preterm birth (PTB). We constructed a retrospective cohort study (N = 16,657) of Iowa Medicaid-insured women who had a singleton live birth from October 2005 to December 2006; 28 % of women received PCM. A PCM dosage measure was created to capture duration of enrollment, total time with a case manager, and intervention breadth. Propensity score (PS)-adjusted odds ratios (ORs), and 95 % confidence intervals (95 % CIs) were calculated to assess the risk of each outcome by PCM dosage and the dichotomous PCM exposure measure. PS-adjusted ORs of PTB were 0.88 (95 % CI 0.70-1.11), 0.58 (95 % CI 0.47-0.72), and 1.43 (95 % CI 1.23-1.67) for high, medium, and low PCM dosage, respectively. For LBW, the PS-adjusted ORs were 0.76 (95 % CI 0.57-1.00), 0.64 (95 % CI 0.50-0.82), and 1.36 (95 % CI 1.14-1.63), for high, medium, and low PCM dosage, respectively. The PCM dichotomous participation measure was not significantly associated with LBW (OR = 0.95, 95 % CI 0.82-1.09) or PTB (0.97, 95 % CI 0.87-1.10). The reference group in each analysis is No PCM. PCM was associated with a reduced risk of adverse pregnancy outcomes for Medicaid-insured women in Iowa. PCM dosage appeared to be a more sensitive measure than the dichotomous measure of PCM participation.
authors.affiliation: Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, East Lansing, MI, USA, jslaughts@gmail.com.
authors.forename: Jaime C
authors.initials: JC
authors.lastname: Slaughter
authors.forename: L Michele
authors.initials: LM
authors.lastname: Issel
authors.forename: Arden S
authors.initials: AS
authors.lastname: Handler
authors.forename: Deborah
authors.initials: D
authors.lastname: Rosenberg
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Kane
authors.forename: Leslie T
authors.initials: LT
authors.lastname: Stayner
mesh_terms: D000293:Adolescent; D000328:Adult; D019090:Case Management / Q000458:organization & administration* / Q000706:statistics & numerical data; D016001:Confidence Intervals; D005260:Female; D006792:House Calls / Q000706:statistics & numerical data*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007484:Iowa; D008484:Medicaid; D016017:Odds Ratio; D010043:Outcome and Process Assessment, Health Care; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth; D011295:Prenatal Care / Q000706:statistics & numerical data*; D057216:Propensity Score; D012189:Retrospective Studies; D012307:Risk Factors; D012959:Socioeconomic Factors; D013997:Time Factors; D014481:United States; D055815:Young Adult