Maternal Weathering and Risk of Preterm Delivery

Objectives. We compared the association between advancing maternal age and risk of preterm delivery across 4 groups (Black smokers, Black nonsmokers, White smokers, White nonsmokers) and within the context of neighborhood deprivation levels.Methods. We obtained data from linked census and birth records for singletons (n = 182 938) delivered by women aged 20 to 39 years in Philadelphia, Pennsylvania; Baltimore, Maryland; 16 Michigan cities; 3 Maryland counties; and 2 North Carolina counties. Results from area-specific multilevel logistic regression models were combined to obtain pooled estimates of relations between maternal age and risk of preterm delivery. We repeated the models after categorizing women by neighborhood deprivation level (low, medium, and high).Results. Among multiparous women, there was a significant age-related increase in preterm delivery in 3 of the 4 groups. The adjusted odds ratio per 5-year age increase was 1.31 in Black smokers, 1.11 in Black nonsmokers, and 1.16 in White smokers. In each group, the odds ratio increased as neighborhood deprivation increased.Conclusions. These results support the “weathering” hypothesis, suggesting that Black women, women with high-risk behaviors, and women living in high-deprivation neighborhoods may develop “accelerated aging” that increases preterm delivery risk.The elevated risks of infant mortality¹ and long-term disability² associated with preterm birth are well-documented. Studies have repeatedly shown higher preterm delivery rates among Black women in the United States³ and women in lower socioeconomic strata.^4–7 The association between preterm delivery risk and maternal age has also been frequently studied by means of data from vital records^8–12 or epidemiologic studies.^13–17 Overall, these studies suggest a curvilinear relation, with slightly higher preterm delivery risk in adolescents, lower risk in early adulthood, and increasing risk with advancing maternal age. The shape of this curve might be influenced by multiple factors, including age-related differences in maternal behaviors and physiologic and disease states. There is also self-selection in timing of pregnancies, and later-age pregnancies may include a higher proportion of women with a history of infertility or fetal loss.Building on the observations that adverse pregnancy outcomes increase with advancing maternal age, and noting the marked Black–White disparities in these adverse outcomes, Geronimus proposed a “weathering” or “accelerated aging” hypothesis.¹⁸ This hypothesis states that: (1) a decline in health status contributes to poorer reproductive outcomes as women age and (2) social inequalities lead to an earlier and disproportionately greater decline in the health status of Blacks, which results in a widening health differential between Blacks and Whites with advancing age. In support of the weathering hypothesis, Geronimus and others have shown an increase in Black–White disparities with advancing maternal age for outcomes such as neonatal mortality^18,19 and low and very low birth weight (LBW),^18,20–23 but results for preterm delivery have been inconsistent.^9,12,24 There have also been reports of increasing disparities in adverse pregnancy outcomes with advancing age when women are categorized by measures of disadvantage or socioeconomic status.^20,23,25Based on the framework described by Williams,²⁶ there are multiple potential causes in the pathway to accelerated aging among Black and disadvantaged women, such as delays in accessing health care, employment-related adverse health effects, more obstacles to and fewer opportunities for a healthy lifestyle (e.g., exercise and diet), exposure to air pollutants, high-risk coping behaviors (e.g., smoking, alcohol use, and drug use), and excess stress caused by discrimination, violence, financial troubles, housing insecurity, and lack of instrumental social support. Many of these causes are endemic, and perhaps “infectious,” in neighborhoods with high levels of deprivation.²⁷ Among previous studies that have examined effects of neighborhood poverty level on the associations among race, maternal age, and risk of LBW deliveries, results have been mixed,^20,22,23 and no study has assessed preterm delivery as the primary outcome.In our study we linked birth records to census data from a multisite project to compare the association between advancing maternal age and risk of preterm delivery across groups of women categorized by race and reported smoking status during pregnancy. Although smoking is thought to have direct effects on preterm delivery risk, we also considered smoking to be a potential indicator of high-risk coping behaviors and unhealthy lifestyle. We also examined effects of neighborhood deprivation on the age–preterm delivery relation within the different maternal groups as defined by race and smoking status. We hypothesized that the slope of increasing preterm delivery risk with advancing maternal age would be steeper for Black women, smokers, and women living in neighborhoods with high levels of deprivation.