In a recent study published in The Lancet, researchers estimated prevalence in 2020 for three mutually exclusive types of small vulnerable newborns [(SVNs); preterm small for gestational age (SGA), term SGA and preterm but non-SGA] using individual-level data (for 2010 to 2020) from 23 national datasets (110 million live births) and 31 studies conducted across 18 nations (0.40 million live births).
Study: Small babies, big risks: global estimates of prevalence and mortality for vulnerable newborns to accelerate change and improve counting. Image Credit: fradis_photo/Shutterstock.com
Background
In each nation across the globe, large numbers of SVNs every year disproportionately contribute to mortality and the long-term loss of human capital. Evaluated using low birth weight (LBW) status, global targets have been set and missed.
More specific SVN types, i.e., preterm SGA, preterm non-SGA, and term SGA, could enable analysis beyond LBW assessments, including pathways for preterm births and fetal growth restrictions (FGRs).
Stillbirths also need to be included in the evaluations. The SVN types could be used to inform individual-level care, improve research precision on etiopathogenesis and interventions, and accelerate progress on primary prevention, thereby improving birth outcomes.
About the study
In the present study, researchers estimated the national-level prevalence of the types of SVNs for the WHO member nations and regions. It then proposed a new framework to categorize the type of newborn based on gestational age, birth weight, and size for GA using Bayesian modeling.
The SVN Series team provided: (i) estimates for preterm births in 2020 and birth patterns over the previous 10 years; (ii) prevalence estimates by SVN type for live births [non-SGA and preterm, including large for gestational age (LGA) and appropriate for GA (AGA); SGA and preterm; and SGA and term; (iii) risk estimates for infant mortality by SVN types and the rates of stillbirths and rate ratio (RR) values across several nations; and (iv) improved evaluation of each baby, in each nation, including stillborn babies.
The assessments were based on an analysis of data obtained from 194 member states of the World Health Organization (WHO), including the Palestinian territory and the eastern parts of Jerusalem (together mentioned as nations and areas). LBW babies’ data were obtained from 81% (n=158) of the WHO nations and areas, and 58% (n=113) of them provided national-level administrative information.
Preterm birth data were obtained from 53% (n=103) of nations and areas, only 33% (n=64) of which provided administrative information at the national level. National-level SGA data were accessible for eight nations.
Region-wise preterm births were assessed for 2020 and the previous 10 years based on WHO and the United Nations Children’s Fund (UNICEF) estimates. Mexico, Brazil, and Argentina had national and sub-national data sets concerning data inputs for vulnerable newborn types and regional and global estimates.
Data obtained from the Vulnerable Newborn Measurement Collaboration were also analyzed. The livebirths were characterized as either of the three types of SVNs, based on the gestational age (i.e., preterm if born earlier than 37.0 weeks and term if born at or after 37.0 weeks) and the size for GA and sex using the INTERGROWTH-21st newborn guidelines (i.e., SGA below the 10th centile or non-SGA equal to or above the 10th centile).
National-level neonatal mortality data were retrieved from 15 datasets (126 million live births) in middle- and high-income nations and 16 sub-national, population-level cohort analyses (238,000 live births) in middle- and low-income regions with exposure data available for the 2000-2020 period.
Results
Worldwide estimates for the year 2020 indicated that 13 million live births were preterm, constituting one in every 10 newborns (10%), with static rates in the previous decade, and 23 million (17%) liveborn babies were SGA.
By region, 41% and 11% of newborns in the southern regions of Asia and the sub-Saharan regions of Africa, respectively, were SGA. The team found that 12 million (8.80%), 22 million (16%), and 1.50 million (1.10%) of global live births were preterm but non-SGA, term and small for gestational age, and pre-term SGA, respectively.
Among 55% of the infant deaths globally in 2020 (2.40 million), 33%, 7.70%, and 15% were observed among preterm but non-SGA, preterm SGA, and term SGA infants, respectively. North America, New Zealand, Australia, Europe, and Central Asia had the greatest number of deaths due to small, vulnerable newborns (68.0%), of which 91% were among preterm infants.
RRs for term SGA infants (2.70 to 3.40) were lower compared to those for preterm but non-SGA infants (4.0 to 12), but they accounted for 21% mortality in the southern parts of Asia and 15% globally.
National-level data from 12 (out of 23) nations (0.60 million stillborn infants at ≥22.0 gestation weeks) indicated that 74% of stillborn infants had preterm births, which included preterm SGA (16%) and term stillbirths (20%) SGA.
Preterm rates varied by region and exceeded the global mean in a few high-income nations, including the United States of America (USA), at 10.0%. There were two million stillbirths each year that showed similar vulnerability pathways.
Most SVNs were identified in the southern regions of Asia (52%) and the sub-Saharan regions of Africa (20%). SVN rates were the lowest in regions with low infant deaths, such as North America, New Zealand, Australia, Europe, and the central regions of Asia (14%). The relative risk (RR) of neonatal mortality was the greatest for preterm babies.
Conclusions
Overall, the study findings highlighted a simplified grouping method based on three mutually exclusive SVN types, i.e., preterm SGA, term SGA, and preterm but non-SGA, without the LBW dimension.
The analysis showed that 99 million live births, 22 million live births, 12 million live births, and 1.50 million live births were term but non-SGA, term SGA, preterm but non-SGA, and preterm SGA, respectively.
Concerning neonatal deaths, 0.2 million, 0.8 million, and 0.4 million deaths occurred among pre-term SGA, preterm non-SGA, term SGA, and term non-SGA infants, respectively. Most stillbirths were preterm or SGA.
Efforts must be taken to lower the SVN burden, which is associated with an increase in life-course complications (e.g., stunting and the risk of non-communicable diseases), disability and reduced learning potential, mortality, and loss of human capital.