Reconstructing a Pregnancy Cohort to Examine Potential Selection Bias in Studies on Racial Disparities in Preterm Delivery

Authors

Katherine J. Sapra, Waterloo Cornell Medical College
Ashok K. Chaurasia, University of Waterloo
Jennifer A. Hutcheon, University of British Columbia
Katherine A. Ahrens PhD, University of Southern Maine, Muskie School of Public ServiceFollow

Document Type

Article

Publication Date

10-29-2016

Publication Title

Paediatric and Perinatal Epidemiology

Keywords

collider bias, induced termination, loss to follow-up, preterm birth, racial disparities, selection bias

Abstract

BACKGROUND: Epidemiologic studies examining preconception risk factors on perinatal outcomes are typically restricted to livebirths. By including only non-terminated pregnancies, estimates for the underlying pregnancy cohort may be subject to selection bias. We examined if potential selection bias due to induced termination by maternal race may result in different estimates of the non-Hispanic black - non-Hispanic white risk ratio (RR) for preterm delivery (PTD) among a reconstructed pregnancy cohort ('pseudo-pregnancy cohort'). METHODS: Using New York City registries of 1.6 million livebirths, spontaneous terminations, and induced terminations among non-Hispanic black and non-Hispanic white women (2000-12), we multiply imputed PTD (<37 >weeks) and early PTD (<32 >weeks) outcomes for induced terminations based on maternal race, age, parity, marital status, nativity, and medical care payer to construct the pseudo-pregnancy cohort. RESULTS: Among non-Hispanic black and non-Hispanic white women, 55% and 19% of pregnancies ended in induced termination and 13% and 8% resulted in PTD, respectively. Although several factors were associated with both PTD and induced termination, PTD RRs in the birth (RR 1.64, 95% confidence interval (CI) 1.62, 1.66) and pseudo-pregnancy (RR 1.63, 95% CI 1.56, 1.71) cohorts were similar. However, early PTD RR was somewhat larger in the birth (RR 2.80, 95% CI 2.71, 2.89) than pseudo-pregnancy (RR 2.47, 95% CI 2.23, 2.73) cohort. CONCLUSIONS: Using birth certificate data - thereby excluding induced terminations - to estimate the PTD racial disparity did not produce biased estimates. Our data suggest observed PTD disparities likely are not artefacts of selection bias due to induced termination.

Comments

© 2016 John Wiley & Sons Ltd.

Recommended Citation

Sapra, K.J., Chaurasia, A.K., Hutcheon, J.A., & Ahrens, K.A. (2017). Reconstructing a pregnancy cohort to examine potential selection bias in studies of racial disparities in preterm delivery. Paediatric and Perinatal Epidemiogy, 31(1), 55-63.