Impact of stillbirths on international comparisons of preterm birth rates: a secondary analysis of the WHO multi-country survey of Maternal and Newborn Health

Objective: To evaluate the extent to which stillbirths affect international comparisons of preterm birth rates in low- and middle-income countries. Design: Secondary analysis of a multi-country cross-sectional study. Setting: 29 countries participating in the World Health Organization Multicountry Survey on Maternal and Newborn Health. Population: 258 215 singleton deliveries in 286 hospitals. Methods: We describe how inclusion or exclusion of stillbirth affect rates of preterm births in 29 countries. Main outcome measures: Preterm delivery. Results: In all countries, preterm birth rates were substantially lower when based on live births only, than when based on total births. However, the increase in preterm birth rates with inclusion of stillbirths was substantially higher in low Human Development Index (HDI) countries [median 18.2%, interquartile range (17.2–34.6%)] compared with medium (4.3%, 3.0–6.7%), and high-HDI countries (4.8%, 4.4–5.5%). Conclusion: Inclusion of stillbirths leads to higher estimates of preterm birth rate in all countries, with a disproportionately large effect in low-HDI countries. Preterm birth rates based on live births alone do not accurately reflect international disparities in perinatal health; thus improved registration and reporting of stillbirths are necessary. Tweetable abstract: Inclusion of stillbirths increases preterm birth rates estimates, especially in low-HDI countries.