title: Maternal exposures in the National Birth Defects Prevention Study: Time trends of selected exposures.
abstract: BACKGROUND
  Our objective was to describe time trends in selected pregnancy exposures in the National Birth Defects Prevention Study (NBDPS).
  
  
  METHODS
  We analyzed data from the NBDPS, a multi-site case-control study of major birth defects, for mothers of live-born infants without birth defects (controls), with an expected date of delivery (EDD) from 1998 to 2011. Mothers from the 10 participating centers across the United States were interviewed by phone between 6 weeks and 2 years after the EDD. We focused on maternal race/ethnicity and five maternal risk factors: obesity, use of folic acid-containing multivitamins, opioid analgesics, selective serotonin reuptake inhibitors, and loratadine because of their prevalence of use and some reports of associations with major birth defects. Prevalence time trends were examined using the Kendall's τβ test statistic.
  
  
  RESULTS
  The exposure trend analysis included 11,724 control mothers with EDDs from 1998 to 2011. We observed a significant increase in obesity prevalence among control mothers, as well as use of selective serotonin reuptake inhibitors and loratadine. We also observed an increase in periconceptional use of folic acid-containing multivitamins. Some of the time trends varied by race/ethnicity. No remarkable trend in the overall use of opioid analgesics was observed. The racial/ethnic distribution of mothers changed slightly during the study period.
  
  
  CONCLUSIONS
  Long-term, population-based case-control studies continue to be an effective way to assess exposure-birth defects associations and provide guidance to health care providers. However, investigators examining rare outcomes covering many years of data collection need to be cognizant of time trends in exposures.
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia.
authors.forename: April L
authors.initials: AL
authors.lastname: Dawson
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia.
authors.forename: Hilda
authors.initials: H
authors.lastname: Razzaghi
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia.|Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee.
authors.forename: Annelise
authors.initials: A
authors.lastname: Arth
authors.affiliation: Birth Defects Epidemiology and Surveillance Branch, Texas Department of State Health Services, Austin, Texas.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Canfield
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Samantha E
authors.initials: SE
authors.lastname: Parker
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia.
authors.forename: Jennita
authors.initials: J
authors.lastname: Reefhuis
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects*; D018926:Anti-Allergic Agents / Q000009:adverse effects; D016022:Case-Control Studies; D000013:Congenital Abnormalities / Q000209:etiology* / Q000517:prevention & control; D005006:Ethnicity; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage; D006801:Humans; D017336:Loratadine / Q000009:adverse effects*; D018811:Maternal Exposure / Q000009:adverse effects*; D009765:Obesity / Q000150:complications*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000209:etiology*; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects*; D013997:Time Factors; D014815:Vitamins / Q000009:adverse effects
chemical_list: D000701:Analgesics, Opioid; D018926:Anti-Allergic Agents; D005492:Folic Acid; D017336:Loratadine; D017367:Selective Serotonin Reuptake Inhibitors; D014815:Vitamins
keywords: birth defects; case control studies; maternal exposure