Socioeconomic and Environmental Determinants to Preterm Birth in Tibetan Women: An Analysis Based on the Hierarchically Conceptual Frame

BACKGROUND Preterm birth is a common cause of death in newborns and may result from many determinants, but evidence for the socioeconomic and environmental determinants of preterm birth in Tibetan women of childbearing age is limited. The aim of this study was to understand the current status of preterm birth in native Tibetan women and investigate the socioeconomic and environmental determinants. METHODS Data were drawn from a cohort study which was conducted from August 2006 to August 2012 in rural Lhasa, Tibet, China. A total of 1419 Tibetan pregnant women were followed from 20 weeks' gestation until delivery; the loss to follow-up rate was 4.69%. The incidence of preterm birth was estimated to show the status of preterm births in Tibet. Logistic regression models for longitudinal data were established, and odds ratios (ORs) together with 95% confidence intervals (CIs) were used to evaluate the association between the occurrence of preterm birth and 16 selected potential determinants based on the hierarchical conceptual frame. RESULTS The incidence of preterm birth was 4.58% (95% CI = 3.55-5.80%). After adjusting for health-related variables of the mothers and newborns, socioeconomic and environmental determinants associated with preterm birth included season (spring: OR = 0.28, 95% CI = 0.09-0.84; autumn: OR = 0.21, 95% CI = 0.06-0.69; and winter: OR = 0.31, 95% CI = 0.12-0.82) and calendar year of delivery (2010: OR = 5.03, 95% CI = 1.24-20.35; 2009: OR = 6.62, 95% CI = 1.75-25.10; and 2007-2008: OR = 5.93, 95% CI = 1.47-23.90). CONCLUSIONS The incidence of preterm birth among native Tibetan women was low and there was a decreasing trend in recent years; however, it is still essential to strengthen seasonal maternal care, extend the spacing between pregnancies, and reinforce adequate maternal nutrition.