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Reconstructing a Pregnancy Cohort to Examine Potential Selection Bias in Studies on Racial Disparities in Preterm Delivery
Author(s) -
Sapra Katherine J.,
Chaurasia Ashok K.,
Hutcheon Jennifer A.,
Ahrens Katherine A.
Publication year - 2017
Publication title -
paediatric and perinatal epidemiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.667
H-Index - 88
eISSN - 1365-3016
pISSN - 0269-5022
DOI - 10.1111/ppe.12322
Subject(s) - medicine , pregnancy , cohort , obstetrics , birth certificate , relative risk , cohort study , demography , confidence interval , gynecology , population , environmental health , genetics , sociology , biology
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 RR s 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.