Birth Defects Cluster Study: a national approach to birth defects cluster investigations.
BACKGROUND
Investigations of clusters of birth defects have been challenging endeavors that have had only modest success identifying causes or risk factors. Some of the challenges to individual cluster investigations have been small sample size and limited data collection. We describe a novel approach for investigating and analyzing pooled information from a series of birth defects cluster investigations.


METHODS
The Birth Defects Cluster Study uses a case-control study design with standardized methods, including a case definition, control selection, data collection methods, and data collected (e.g., maternal interviews, blood samples, and environmental samples). Analyses of pooled data from several clusters of the same defect are conducted for specific hypotheses once a sufficient sample size has been achieved. The feasibility of conducting individual birth defect investigations was evaluated on a cluster of gastroschisis.


RESULTS
The pilot investigation of a cluster of gastroschisis demonstrated success in recruiting participants and in collecting data and specimens for eventual inclusion in a pooled analysis.


CONCLUSIONS
The Birth Defects Cluster Study offers a unique and effective approach to cluster investigations that improves the likelihood of identifying genetic and environmental causes of birth defects and provides a model for cluster investigations of other noninfectious health outcomes.
Kucik
James E
JE
Division of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, Atlanta, Georgia 30333, USA. jkucik@cdc.gov
Bitsko
Rebecca H
RH
Williams
Laura
L
Lazarus
Carrie
C
Jarman
Dwayne W
DW
Correa
Adolfo
A
D016022:Case-Control Studies; D016000:Cluster Analysis; D000013:Congenital Abnormalities / Q000175:diagnosis / Q000453:epidemiology*; D003625:Data Collection; D005260:Female; D006801:Humans; D010865:Pilot Projects; D011159:Population Surveillance; D011247:Pregnancy; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors