title: Population-based microcephaly surveillance in the United States, 2009 to 2013: An analysis of potential sources of variation.
abstract: BACKGROUND
  Congenital microcephaly has been linked to maternal Zika virus infection. However, ascertaining infants diagnosed with microcephaly can be challenging.
  
  
  METHODS
  Thirty birth defects surveillance programs provided data on infants diagnosed with microcephaly born 2009 to 2013. The pooled prevalence of microcephaly per 10,000 live births was estimated overall and by maternal/infant characteristics. Variation in prevalence was examined across case finding methods. Nine programs provided data on head circumference and conditions potentially contributing to microcephaly.
  
  
  RESULTS
  The pooled prevalence of microcephaly was 8.7 per 10,000 live births. Median prevalence (per 10,000 live births) was similar among programs using active (6.7) and passive (6.6) methods; the interdecile range of prevalence estimates was wider among programs using passive methods for all race/ethnicity categories except Hispanic. Prevalence (per 10,000 live births) was lowest among non-Hispanic Whites (6.5) and highest among non-Hispanic Blacks and Hispanics (11.2 and 11.9, respectively); estimates followed a U-shaped distribution by maternal age with the highest prevalence among mothers <20 years (11.5) and ≥40 years (13.2). For gestational age and birth weight, the highest prevalence was among infants <32 weeks gestation and infants <1500 gm. Case definitions varied; 41.8% of cases had an HC ≥ the 10thpercentile for sex and gestational age.
  
  
  CONCLUSIONS
  Differences in methods, population distribution of maternal/infant characteristics, and case definitions for microcephaly can contribute to the wide range of observed prevalence estimates across individual birth defects surveillance programs. Addressing these factors in the setting of Zika virus infection can improve the quality of prevalence estimates. Birth Defects Research (Part A) 106:972-982, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Janet D
authors.initials: JD
authors.lastname: Cragan
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.|Carter Consulting Inc., Atlanta, Georgia.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Isenburg
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: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: C J
authors.initials: CJ
authors.lastname: Alverson
authors.affiliation: State Center for Health Statistics, N.C. Division of Public Health, Raleigh, North Carolina.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Meyer
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.|Carter Consulting Inc., Atlanta, Georgia.
authors.forename: Erin B
authors.initials: EB
authors.lastname: Stallings
authors.affiliation: Department of Community and Family Health, College of Public Health, University of South Florida, Tampa, Florida.
authors.forename: Russell S
authors.initials: RS
authors.lastname: Kirby
authors.affiliation: Section of Hematology-Oncology, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Lupo
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.|Leidos Holdings, Inc., Reston, Virginia.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Liu
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.|Carter Consulting Inc., Atlanta, Georgia.
authors.forename: Amanda
authors.initials: A
authors.lastname: Seagroves
authors.affiliation: Birth Defects Epidemiology and Surveillance Branch, Texas Department of State Health Services, Austin, Texas.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Ethen
authors.affiliation: Division of Community and Family Health, Minnesota Department of Health, St. Paul, Minnesota.
authors.forename: Sook Ja
authors.initials: SJ
authors.lastname: Cho
authors.affiliation: Oregon Birth Anomalies Surveillance System, Oregon Public Health Division, Portland, Oregon.
authors.forename: MaryAnn
authors.initials: M
authors.lastname: Evans
authors.affiliation: Center for Birth Defects Research and Prevention, Massachusetts Department of Public Health, Boston, Massachusetts.
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Liberman
authors.affiliation: Division of Epidemiologic Studies, Illinois Department of Public Health, Springfield, Illinois.
authors.forename: Jane
authors.initials: J
authors.lastname: Fornoff
authors.affiliation: New York State Department of Health, Albany, New York.
authors.forename: Marilyn L
authors.identifier: http://orcid.org/0000-0002-1872-2787
authors.initials: ML
authors.lastname: Browne
authors.affiliation: Department of Community and Family Health, College of Public Health, University of South Florida, Tampa, Florida.
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Rutkowski
authors.affiliation: Utah Birth Defect Network, Division of Family Health and Preparedness, Utah Department of Health, Salt Lake City, Utah.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Nance
authors.affiliation: National Birth Defects Prevention Network, Houston, Texas.
authors.forename: Marlene
authors.initials: M
authors.lastname: Anderka
authors.affiliation: New York State Department of Health, Albany, New York.
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Fox
authors.affiliation: Utah Birth Defect Network, Division of Family Health and Preparedness, Utah Department of Health, Salt Lake City, Utah.
authors.forename: Amy
authors.initials: A
authors.lastname: Steele
authors.affiliation: Division for Vital Records and Health Statistics, Michigan Department of Health and Human Services, Lansing, Michigan.
authors.forename: Glenn
authors.initials: G
authors.lastname: Copeland
authors.affiliation: College of Public Health, University of Iowa, Iowa City, Iowa.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Romitti
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Cara T
authors.initials: CT
authors.lastname: Mai
mesh_terms: D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008831:Microcephaly / Q000453:epidemiology*; D015995:Prevalence; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology; D000071244:Zika Virus; D000071243:Zika Virus Infection / Q000453:epidemiology*
keywords: head circumference; microcephaly; prevalence; surveillance