Stillbirths: Contribution of preterm birth and size‐for‐gestational age for 125.4 million total births from nationwide records in 13 countries, 2000–2020

Abstract

AbstractObjectiveTo examine the contribution of preterm birth and size‐for‐gestational age in stillbirths using six ‘newborn types’.DesignPopulation‐based multi‐country analyses.SettingBirths collected through routine data systems in 13 countries.Sample125 419 255 total births from 22+0 to 44+6 weeks’ gestation identified from 2000 to 2020.MethodsWe 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 measuresDistribution of stillbirths, stillbirth rates and rate ratios according to six newborn types.Results635 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.ConclusionsIn 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.