title: Methodology for establishing a population-based birth cohort focusing on couple fertility and children's development, the Upstate KIDS Study.
abstract: BACKGROUND
  Critical data gaps remain regarding infertility treatment and child development. We assessed the utility of a birth certificate registry for developing a population cohort aimed at answering such questions.
  
  
  METHODS
  We utilised the Upstate New York livebirth registry (n = 201,063) to select births conceived with (n = 4024) infertility treatment or exposed infants, who were then frequency-matched by residence to a random sample of infants conceived without (n = 14,455) treatment or unexposed infants, 2008-10. Mothers were recruited at 2-4 months postpartum and queried about their reproductive histories, including infertility treatment for comparison with birth certificate data. Overall, 1297 (32%) mothers of exposed and 3692 of unexposed (26%) infants enrolled.
  
  
  RESULTS
  Twins represented 22% of each infant group. The percentage of infants conceived with/without infertility treatment was similar whether derived from the birth registry or maternal report: 71% none, 16% drugs or intrauterine insemination, and 14% assisted reproductive technologies (ART). Concordant reporting between the two data sources was 93% for no treatment, 88% for ART, and 83% for fertility drugs, but differed by plurality. Exposed infants had slightly (P < 0.01) earlier gestations than unexposed infants (38.3 ± 2.8 and 38.7 ± 2.7 weeks, respectively) based upon birth certificates but not maternal report (38.7 ± 2.7 and 38.7 ± 2.9, respectively). Conversely, mean birthweight was comparable using birth certificates (3157 ± 704 and 3194 ± 679 g, respectively), but differed using maternal report (3167 ± 692 and 3224 ± 661, respectively P < 0.05).
  
  
  CONCLUSIONS
  The birth certificate registry is a suitable sampling framework as measured by concordance with maternally reported infertility treatment. Future efforts should address the impact of factors associated with discordant reporting on research findings.
authors.affiliation: Division of Intramural Population Health Research, Rockville, MD.
authors.forename: Germaine M
authors.initials: GM
authors.lastname: Buck Louis
authors.forename: Mary L
authors.initials: ML
authors.lastname: Hediger
authors.forename: Erin M
authors.initials: EM
authors.lastname: Bell
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Kus
authors.forename: Rajeshwari
authors.initials: R
authors.lastname: Sundaram
authors.forename: Alexander C
authors.initials: AC
authors.lastname: McLain
authors.forename: Edwina
authors.initials: E
authors.lastname: Yeung
authors.forename: Elaine A
authors.initials: EA
authors.lastname: Hills
authors.forename: Marie E
authors.initials: ME
authors.lastname: Thoma
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: Druschel
mesh_terms: D000328:Adult; D001719:Birth Certificates; D001723:Birth Rate; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D005191:Family Characteristics; D005260:Female; D005298:Fertility; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009099:Multiple Birth Offspring / Q000706:statistics & numerical data*; D009518:New York / Q000453:epidemiology; D011159:Population Surveillance; D011247:Pregnancy; D011256:Pregnancy Outcome; D012042:Registries; D027724:Reproductive Techniques, Assisted / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D014427:Twins
keywords: assisted reproductive technologies; children; fecundity; in vitro fertilization; infertility