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Twinning and major birth defects, National Birth Defects Prevention Study, 1997–2007
Journal article   Peer reviewed

Twinning and major birth defects, National Birth Defects Prevention Study, 1997–2007

April L Dawson, Sarah C Tinker, Denise J Jamieson, Charlotte A Hobbs, R J Berry, Sonja A Rasmussen, Marlene Anderka, Kim M Keppler-Noreuil, Angela E Lin, Jennita Reefhuis, …
Journal of epidemiology and community health (1979), Vol.70(11), pp.1114-1121
11/01/2016
DOI: 10.1136/jech-2015-206302
PMCID: PMC5299593
PMID: 27325867
url
https://www.ncbi.nlm.nih.gov/pmc/articles/5299593View
Open Access

Abstract

BackgroundTwinning has been associated with many types of birth defects, although previous studies have had inconsistent findings. Many studies lack information about potential confounders, particularly use of fertility treatment. Our objective was to assess the association between twinning and birth defects in the National Birth Defects Prevention Study (NBDPS).MethodsWe used data from the NBDPS, a population-based, case–control study of major birth defects in the USA, to evaluate associations between twinning and birth defects. The study population included mothers of twin and singleton controls (live-born infants without major birth defects), and cases (fetuses or infants with a major birth defect) born October 1997–December 2007. Adjusted ORs and 95% CIs were estimated using multivariable logistic regression stratified by use of fertility treatment. Twin sex-pairing data and a simulation approach were used to estimate the zygosity of twins.ResultsIn the unassisted conception stratum, we observed significant positive associations between twinning and 29 of 45 defect groups. The largest effect estimates were observed for multiple ventricular septal defects and cloacal exstrophy. Among mothers reporting any use of fertility treatments, we observed a significant association with twinning for 5 of 25 defect groups, with the largest effect estimates for hypoplastic left heart syndrome and omphalocele. OR estimates in the estimated monozygotic stratum were generally further from the null than in the dizygotic stratum.ConclusionsCompared with singletons, a wide range of birth defects are significantly more common among twins. Birth defect risk in twins may be differential by use of fertility treatment.

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