title: Control selection and participation in an ongoing, population-based, case-control study of birth defects: the National Birth Defects Prevention Study.
abstract: To evaluate the representativeness of controls in an ongoing, population-based, case-control study of birth defects in 10 centers across the United States, researchers compared 1997-2003 birth certificate data linked to selected controls (n = 6,681) and control participants (n = 4,395) with those from their base populations (n = 2,468,697). Researchers analyzed differences in population characteristics (e.g., percentage of births at > or =2,500 g) for each group. Compared with their base populations, control participants did not differ in distributions of maternal or paternal age, previous livebirths, maternal smoking, or diabetes, but they did differ in other maternal (i.e., race/ethnicity, education, entry into prenatal care) and infant (i.e., birth weight, gestational age, and plurality) characteristics. Differences in distributions of maternal, but not infant, characteristics were associated with participation by selected controls. Absolute differences in infant characteristics for the base population versus control participants were < or =1.3 percentage points. Differences in infant characteristics were greater at centers that selected controls from hospitals compared with centers that selected controls from electronic birth certificates. These findings suggest that control participants in the National Birth Defects Prevention Study generally are representative of their base populations. Hospital-based control selection may slightly underascertain infants affected by certain adverse birth outcomes.
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA 30329-4027, USA. mcogswell@cdc.gov
authors.forename: Mary E
authors.initials: ME
authors.lastname: Cogswell
authors.forename: Rebecca H
authors.initials: RH
authors.lastname: Bitsko
authors.forename: Marlene
authors.initials: M
authors.lastname: Anderka
authors.forename: Alissa R
authors.initials: AR
authors.lastname: Caton
authors.forename: Marcia L
authors.initials: ML
authors.lastname: Feldkamp
authors.forename: Stacey M
authors.initials: SM
authors.lastname: Hockett Sherlock
authors.forename: Robert E
authors.initials: RE
authors.lastname: Meyer
authors.forename: Tunu
authors.initials: T
authors.lastname: Ramadhani
authors.forename: James M
authors.initials: JM
authors.lastname: Robbins
authors.forename: Gary M
authors.initials: GM
authors.lastname: Shaw
authors.forename: T J
authors.initials: TJ
authors.lastname: Mathews
authors.forename: Marjorie
authors.initials: M
authors.lastname: Royle
authors.forename: Jennita
authors.initials: J
authors.lastname: Reefhuis
mesh_terms: D001719:Birth Certificates; D016022:Case-Control Studies; D000013:Congenital Abnormalities / Q000453:epidemiology* / Q000517:prevention & control; D003625:Data Collection; D005260:Female; D006753:Hospital Records; D006801:Humans; D007231:Infant, Newborn; D050498:Live Birth / Q000453:epidemiology; D011247:Pregnancy; D014481:United States / Q000453:epidemiology