Determinants of Preterm Births at a National Hospital in Zambia: Application of Partial Proportional Odds Model

Author(s): Moses Mukosha, Choolwe Jacobs, Patrick Musonda, John Mathias Zulu, Sheila Masaku, Chipo Nkwemu, Bellington Vwalika, Kunda Mutesu Kapembwa, Patrick Kaonga

Background: Preterm birth (PTB), the delivery of a baby before 37 completed weeks of gestation, is responsible for increased childhood morbidity and mortality globally. However, in most developing countries, the determinats of PTB are usually underestimated and content-specific. Therefore, we assessed the determinants of ordered preterm birth levels at the Women and Newborn Teaching Hospital, Lusaka, Zambia.

Methods: We reviewed admission and delivery registers from 1st January 2018 to 30th September 2019 for birth records. Preterm births were in four categories; term, moderate, late preterm and very preterm. We assessed the determinants of ordered levels of preterm birth using the partial proportional odds regression model. Data were analysed using Stata version 16, and statistical tests were done using 5% significance level and 95% confidence interval.

Results: The study included a total of 3243 case records of women with a median age of 26 years (IQR, 22-33), of whom 399 (12.3%) delivered very preterm infants, 914 (28.18%) delivered moderate-term infants, 957 (29.51%) delivered late-term infants and 973 (30%) delivered term infants. There were disparities across infants born to HIV uninfected and HIV infected women, with the latter being more likely to be on the lower levels of preterm birth. However, attending antenatal clinic and a unit increase in maternal age were more likely to be on the higher levels of preterm birth. Pre-eclampsia's effect was not constant across the binary logistic regression models but generally showed a reduced odds of being in higher preterm birth levels for women with the condition.

Conclusion: HIV infection and pre-eclampsia predict lower preterm birth levels while attending antenatal care (ANC), and increased maternal age is protective. Pregnant women presenting with pre-eclampsia and HIV infection should receive special consider