The association between maternal and paternal race and preterm birth.
Non-Hispanic black maternal race is a known risk factor for preterm birth. However, the contribution of paternal race is not as well established.
We sought to evaluate the risk of preterm birth among non-Hispanic black, non-Hispanic white, and mixed non-Hispanic black and non-Hispanic white dyads.
This was a population-based cohort study of all live births in the United States from 2015 to 2017, using live birth records from the National Vital Statistics System. Singleton, nonanomalous infants whose live birth record included maternal and paternal self-reported race as either non-Hispanic white or non-Hispanic black were included. The primary outcome was preterm birth at <37 weeks' gestation; secondary outcomes included preterm birth at <34 and <28 weeks' gestation and delivery gestational age (as a continuous variable). Data were analyzed using chi-square, t test, analysis of variance, and logistic regression. A Kaplan-Meier survival curve was also generated.
There were 11,809,599 live births during the study period; 4,008,622 births met the inclusion criteria. Of included births, 291,647 (7.3%) occurred at <37 weeks' gestation. Using the convention of maternal race first followed by paternal race, preterm birth at <37 weeks' gestation was most common among non-Hispanic black and non-Hispanic black dyads (n=70,987 [10.8%]), followed by non-Hispanic black and non-Hispanic white (n=3137 [9.5%]), non-Hispanic white and non-Hispanic black (n=9136 [8.3%]), and non-Hispanic white and non-Hispanic white dyads (n=209,387 [6.5%]; P<.001 for trend). Births at <34 weeks' (n=74,474) and <28 weeks' gestation (n=18,474) were also more common among non-Hispanic black and non-Hispanic black dyads. Specifically, 24,351 (3.7%) non-Hispanic black and non-Hispanic black, 1017 (3.1%) non-Hispanic black and non-Hispanic white, 2408 (2.2%) non-Hispanic white and non-Hispanic black, and 46,698 non-Hispanic white and non-Hispanic white dyads delivered at <34 weeks' gestation, and 7988 non-Hispanic black and non-Hispanic black (1.2%), 313 (1.0%) non-Hispanic black and non-Hispanic white, 584 (0.5%) non-Hispanic white and non-Hispanic black, and 9589 (0.3%) non-Hispanic white and non-Hispanic white dyads delivered at <28 weeks' gestation. Non-Hispanic white and non-Hispanic white dyads delivered at a mean 38.8± standard deviation of 1.7 weeks' gestation, although non-Hispanic white and non-Hispanic black, non-Hispanic black and non-Hispanic white, and non-Hispanic black and non-Hispanic black dyads delivered at 38.6±2.0, 38.5±2.3, and 38.3±2.4 weeks' gestation, respectively (P<.001). Adjusted odds ratios for the association between maternal or paternal race and preterm birth were highest for non-Hispanic black and non-Hispanic black dyads at each gestational age cutoff: adjusted odds ratio, 1.60 (95% confidence interval, 1.11-1.19) (<37 weeks' gestation); adjusted odds ratio, 2.47 (95% confidence interval, 2.41-2.53) (<34 weeks' gestation); and adjusted odds ratio, 4.22 (95% confidence interval, 4.04-4.41) (<28 weeks' gestation) compared with the non-Hispanic white referent group. Models adjusted for insurance status, chronic hypertension, tobacco use during pregnancy, history of previous preterm birth, and male fetus. In the Kaplan-Meier survival analysis, non-Hispanic black and non-Hispanic black dyads delivered the earliest across the range of delivery gestational ages compared with all other combinations of dyads.
Non-Hispanic black paternal race is a risk factor for preterm birth and should be considered when evaluating maternal a priori risk of prematurity. Future research should investigate the mechanisms behind this finding, including determining the contribution of factors, such as racism, maternal and paternal genetics, and epigenetics to an individual's risk of preterm birth.
Green CA
，Johnson JD
，Vladutiu CJ
，Manuck TA
... -
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Contribution of maternal cardiometabolic risk factors to racial-ethnicity disparities in preterm birth subtypes.
There are recognized racial-ethnic disparities in preterm birth and in maternal cardiometabolic risk factors likely linked to systemic racism. However, it is unclear the extent to which cardiometabolic risk factors contribute to the higher rates of preterm birth among minoritized populations.
This study aimed to evaluate racial-ethnic disparities in preterm birth subtypes and the role of maternal cardiometabolic risk factors as mediators of the association between maternal race-ethnicity and preterm birth subtypes.
This was a retrospective cohort study of 295,210 singleton live births from 2011 to 2018. Preterm birth subtypes were defined as medically indicated and spontaneous preterm birth. Poisson regression with robust standard errors were used to provide estimates of the relative risks and 95% confidence intervals for preterm birth subtypes. Causal mediation analysis used logistic regression models to estimate the natural direct and natural indirect (mediated) effects of maternal cardiometabolic risk factors.
Compared with White individuals, Black, Asian, and Hispanic individuals were at increased risk for having both medically indicated preterm birth (1.45, 1.30-1.61; 1.21, 1.12-1.31; and 1.13, 1.05-1.22, respectively) (risk ratios, 95% confidence intervals, respectively) and spontaneous preterm birth (1.20, 1.08-1.34; 1.34, 1.26-1.43; and 1.16, (1.08-1.23), independent of established risk factors. The extent to which cardiometabolic risk factors mediated the associations between race-ethnicity (each group vs White in separate analyses) and preterm birth subtypes varied by race-ethnicity. Hypertensive disorders mediated 30.1% of the association between Black race-ethnicity and medically indicated preterm birth, but it did not mediate the association for other racial-ethnic groups or for spontaneous preterm birth. Any glucose disorder in pregnancy was a mediator of medically indicated preterm birth and spontaneous preterm birth for Asian (65.8% and 13.9%, respectively) and Hispanic (17.3% and 11.9%) race-ethnicity but not for Black race-ethnicity. Overweight or obesity mediated the association between race-ethnicity and medically indicated preterm birth (15.5% among Black individuals and 25.1% among Hispanic individuals) and spontaneous preterm birth (10.7% among Hispanic individuals) but was not a mediator among Asian individuals.
Black, Asian, and Hispanic individuals are at increased risk for preterm birth. Maternal cardiometabolic risk factors partially mediate the associations between race-ethnicity and preterm birth subtypes but the extent varies by race-ethnicity. These findings suggest that strategies that improve and diminish differences in cardiometabolic health between race-ethnicity populations may diminish disparities in preterm birth.
Hedderson MM
，Xu F
，Dayo OM
，Liu E
，Sridhar S
，Lee C
，Greenberg M
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