Abstract

OBJECTIVE: To examine the contribution of preterm birth and size-for-gestational age in stillbirths using six 'newborn types'. DESIGN: Population-based multi-country analyses. SETTING: Births collected through routine data systems in 13 countries. SAMPLE: 125?419?255 total births from 22+0 to 44+6 weeks' gestation identified from 2000 to 2020. METHODS: We included 635?107 stillbirths from 22+0?weeks' gestation from 13 countries. We classified all births, including stillbirths, into six 'newborn types' based on gestational age information (preterm, PT, <37+0?weeks versus term, T, ?37+0?weeks) and size-for-gestational age defined as small (SGA, <10th centile), appropriate (AGA, 10th-90th centiles) or large (LGA, >90th centile) for gestational age, according to the international newborn size for gestational age and sex INTERGROWTH-21st standards. MAIN OUTCOME MEASURES: Distribution of stillbirths, stillbirth rates and rate ratios according to six newborn types. RESULTS: 635?107 (0.5%) of the 125?419?255 total births resulted in stillbirth after 22+0?weeks. Most stillbirths (74.3%) were preterm. Around 21.2% were SGA types (PT?+?SGA [16.2%], PT?+?AGA [48.3%], T?+?SGA [5.0%]) and 14.1% were LGA types (PT?+?LGA [9.9%], T?+?LGA [4.2%]). The median rate ratio (RR) for stillbirth was highest in PT?+?SGA babies (RR 81.1, interquartile range [IQR], 68.8-118.8) followed by PT?+?AGA (RR 25.0, IQR, 20.0-34.3), PT?+?LGA (RR 25.9, IQR, 13.8-28.7) and T?+?SGA (RR 5.6, IQR, 5.1-6.0) compared with T?+?AGA. Stillbirth rate ratios were similar for T?+?LGA versus T?+?AGA (RR 0.7, IQR, 0.7-1.1). At the population level, 25% of stillbirths were attributable to small-for-gestational-age. CONCLUSIONS: In these high-quality data from high/middle income countries, almost three-quarters of stillbirths were born preterm and a fifth small-for-gestational age, with the highest stillbirth rates associated with the coexistence of preterm and SGA. Further analyses are needed to better understand patterns of gestation-specific risk in these populations, as well as patterns in lower-income contexts, especially those with higher rates of intrapartum stillbirth and SGA. © 2023 The Authors. BJOG: An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd.