Risks of preterm birth among non-Hispanic black and non-Hispanic white women: Effect modification by maternal age

Amaris M Keiser; Yasmmyn D Salinas; Andrew T DeWan; Nicola L Hawley; Pamela K Donohue; Donna M Strobino

doi:10.1111/ppe.12572

Risks of preterm birth among non-Hispanic black and non-Hispanic white women: Effect modification by maternal age

Paediatr Perinat Epidemiol. 2019 Sep;33(5):346-356. doi: 10.1111/ppe.12572. Epub 2019 Jul 31.

Authors

Amaris M Keiser¹, Yasmmyn D Salinas², Andrew T DeWan², Nicola L Hawley², Pamela K Donohue^{1

3}, Donna M Strobino³

Affiliations

¹ Division of Neonatology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland.
² Department of Chronic Disease Epidemiology, Yale School of Public Health, New Haven, Connecticut.
³ Department of Population, Family and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.

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.

Keywords: black; disparities; maternal age; preterm birth; weathering.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Black or African American*
Cross-Sectional Studies
Educational Status
Female
Humans
Infant, Newborn
Maternal Age
Obesity / epidemiology*
Pregnancy
Premature Birth / epidemiology*
Prenatal Care / statistics & numerical data*
Reference Standards
Risk Factors
Smoking / epidemiology*
Socioeconomic Factors
United States / epidemiology
White People*
Young Adult

Grants and funding

T32 HD007094/HD/NICHD NIH HHS/United States