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Risks of preterm birth among non‐Hispanic black and non‐Hispanic white women: Effect modification by maternal age
Author(s) -
Keiser Amaris M.,
Salinas Yasmmyn D.,
DeWan Andrew T.,
Hawley Nicola L.,
Donohue Pamela K.,
Strobino Donna M.
Publication year - 2019
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.12572
Subject(s) - medicine , demography , poisson regression , confidence interval , relative risk , confounding , ethnic group , population , environmental health , sociology , anthropology
Abstract Background Preterm birth (PTB) disproportionately affects African American compared with Caucasian women, although reasons for this disparity remain unclear. Some suggest that a differential effect of maternal age by race/ethnicity, especially at older maternal ages, may explain disparities. Objective To determine whether the relationship between maternal age and preterm birth varies by race/ethnicity among primiparae non‐Hispanic blacks (NHB) and non‐Hispanic whites (NHW). Methods A cross‐sectional study of 367 081 singleton liveborn first births to NHB and NHW women in California from 2008 to 2012 was conducted. Rate ratios (RR) were estimated for PTB and its subtypes—spontaneous and clinician‐initiated—after adjusting for confounders through Poisson regression. Universal age/race reference groups (NHW, 25‐29 years) and race‐specific reference groups (NHW or NHB, 25‐29 years) were used for comparisons. Results Among all women, RR of PTB was highest at the extremes of age (<15 and ≥40 years). Among NHBs, the risk of PTB was higher than among NHWs at all maternal ages (adjusted RR of PTB 1.38‐2.93 vs 0.98‐2.38). However, using race‐specific reference groups, the risk of PTB for NHB women (RR 0.91‐1.88) vs NHW women (RR 0.98‐2.39) was nearly identical at all maternal ages, with overlapping confidence intervals. Analyses did not demonstrate substantial divergence of risk with advancing maternal age. PTB, spontaneous PTB, and clinician‐initiated PTB demonstrated similar risk patterns at younger but not older maternal ages, where risk of clinician‐initiated PTB increased sharply for all women. Conclusions Primiparae NHBs demonstrated increased risk of PTB, spontaneous PTB, and clinician‐initiated PTB compared with NHWs at all maternal ages. However, RRs using race‐specific reference groups converged across maternal ages, indicating a similar independent effect of maternal age on PTB by race/ethnicity. A differential effect of maternal age does not appear to explain disparities in preterm birth by race/ethnicity.