Preterm birth among pregnant women living in areas with high social vulnerability

Communities and individuals widely vary in their resources and ability to respond to external stressors and insults. To identify vulnerable communities, the Centers for Disease Control and Prevention developed the Social Vulnerability Index, an integrated tool to assess community resources and preparedness; it is based on 15 factors and includes individual scores in the following 4 themes: socioeconomic status (theme 1), household composition and disability (theme 2), minority status and language (theme 3), and housing type and transportation (theme 4) and an overall composite score. Several Social Vulnerability Index components have been independently associated with an increased risk of preterm birth.

We sought to investigate the association of the Social Vulnerability Index for each patient's residence during pregnancy, personal clinical risk factors, and preterm birth.

This was a retrospective cohort study of women carrying nonanomalous singleton or twin gestations delivering at a large university health system from April 2014 to January 2020. Women at high risk of spontaneous and medically indicated preterm birth were assigned to a census tract based on their geocoded home address, and a Social Vulnerability Index score was assigned to each individual by linking each patient's home address at the census tract level. Higher scores indicate greater social vulnerability. The primary outcome was preterm birth at <37 weeks' gestation; secondary outcomes were preterm birth at <34 and <28 weeks' gestation and composite major neonatal morbidity before initial hospital discharge (death, intraventricular leukomalacia or intraventricular hemorrhage, necrotizing enterocolitis, or bronchopulmonary dysplasia). Data were analyzed using the chi-square test, t test, and backward stepwise logistic regression. In addition, because race is a social construct, we conducted regression models omitting Black race. For all regression models, independent variables with a P value of <.20 remained in the final models.

Overall, 15,364 women met the inclusion criteria, of which 18.5%, 6.5%, 2.1% of women delivered at <37, <34, and <28 weeks' gestation, respectively, and 3.1% of neonates were diagnosed with major composite morbidity. Women delivering before term at <37, <34, and <28 weeks' gestation were more likely to live in an area with a higher overall Social Vulnerability Index and higher social vulnerability in each Social Vulnerability Index theme. In regression models, the adjusted odds ratio of preterm birth increased with increasing Social Vulnerability Index scores (across all themes and the composite value); these effects were the greatest at the earliest gestational ages (eg, for the composite Social Vulnerability Index: adjusted odds ratio of preterm birth at <37 weeks' gestation for models, including Black race, 1.32 [95% confidence interval, 1.14-1.53]; adjusted odds ratio at <34 weeks' gestation, 1.60 [95% confidence interval, 1.27-2.01]; adjusted odds ratio at <28 weeks' gestation, 2.21 [95% confidence interval, 1.50-3.25]; adjusted odds ratio for composite major neonatal morbidity, 2.30 [95% confidence interval, 1.67-3.17]). Similar trends were seen for each Social Vulnerability Index theme. In addition, an increased adjusted odds ratio of composite major neonatal morbidity was recognized for each Social Vulnerability Index theme. Results were similar when Black race was removed from the models.

The Social Vulnerability Index is a valuable tool that may further identify communities and individuals at the highest risk of preterm birth and may enable clinicians to integrate information regarding the local home environment of their patients to further refine preterm birth risk assessment.