Cervical pathways for racial disparities in preterm births: the Preterm Prediction Study

J Matern Fetal Neonatal Med. 2019 Dec;32(23):4022-4028. doi: 10.1080/14767058.2018.1484091. Epub 2018 Jul 1.


Purpose: Racial disparities in preterm birth have been long recognized, but the social and biological mechanisms for these differences are unclear. Our analysis had three goals: (1) to determine the relation between race and other social risk factors and cervical structure; (2) to determine whether social factors mediate the relation between race and cervical structure; and (3) to determine whether racial disparities in preterm birth (PTB) are mediated through changes in cervical structure observed earlier in pregnancy. Materials and methods: Data from the Maternal Fetal Medicine Unit network Preterm Prediction Study were used to examine the relation between race and other social factors and cervical properties throughout pregnancy in 2920 black and white women. Outcomes included cervical length and dilation; cervical score (cervical length-internal dilation); and whether membranes protruded at 22-24 and 26-29 weeks. Race, education, income, insurance type, and marital status were examined as predictors of the outcomes using linear and logistic regression, adjusting for age, BMI, parity, and smoking. Mediation analysis was used to examine whether (a) any social factors explained racial differences in cervical properties, and (b) whether cervical properties mediated racial differences in risk for preterm birth. Results: Shorter cervical length, especially at a subject's first visit, was associated with black race (adjusted beta -1.56 mm, p < .01) and lower income (adjusted beta -1.48, p =.05). External dilation was not associated with social factors, while internal dilation was associated with black race and lower education. Black race and marital status were associated with lower cervical score. There was no evidence of mediation of the racial effect on cervical properties by any social factor. Shorter cervical length, dilation, and score were all associated with preterm birth (p < .01). Mediation analysis indicated that each of these mediated the effect of race, but explained a small proportion of the total effect (15-25%). Conclusions: Race, and, to a lesser extent, other social factors are correlated with adverse cervical properties. This pathway could explain a proportion of the racial disparity in preterm birth.

Keywords: Cervix uteri; continental population groups; obstetric labor; premature; premature birth; social determinants of health.

MeSH terms

  • Adult
  • Black or African American / statistics & numerical data
  • Cervical Length Measurement* / methods
  • Cervical Length Measurement* / standards
  • Cervical Length Measurement* / statistics & numerical data
  • Cervix Uteri / diagnostic imaging
  • Cervix Uteri / pathology*
  • Cohort Studies
  • Female
  • Health Status Disparities*
  • Humans
  • Infant, Newborn
  • Pregnancy
  • Pregnancy Outcome / ethnology
  • Pregnancy Trimester, Second / ethnology
  • Pregnancy Trimester, Third / ethnology
  • Premature Birth / diagnosis*
  • Premature Birth / ethnology*
  • Premature Birth / pathology
  • Prenatal Care / statistics & numerical data
  • Prognosis
  • Racial Groups / statistics & numerical data*
  • Risk Factors
  • Socioeconomic Factors
  • White People / statistics & numerical data
  • Young Adult