Influence of different methods for calculating gestational age at birth on prematurity and small for gestational age proportions: a systematic review with meta-analysis

Abstract

Background Recognizing premature newborns and small-for-gestational-age (SGA) is essential for providing care and supporting public policies. This systematic review aims to identify the influence of the last menstrual period (LMP) compared to ultrasonography (USG) before 24 weeks of gestation references on prematurity and SGA proportions at birth. Methods Systematic review with meta-analysis followed the recommendations of the PRISMA Statement. PubMed, BVS, LILACS, Scopus-Elsevier, Embase-Elsevier, and Web-of-Science were searched (10–30-2022). The research question was: (P) newborns, (E) USG for estimating GA, (C) LMP for estimating GA, and (O) prematurity and SGA rates for both methods. Independent reviewers screened the articles and extracted the absolute number of preterm and SGA infants, reference standards, design, countries, and bias. Prematurity was birth before 37 weeks of gestation, and SGA was the birth weight below the p10 on the growth curve. The quality of the studies was assessed using the New-Castle-Ottawa Scale. The difference between proportions estimated the size effect in a meta-analysis of prevalence. Results Among the 642 articles, 20 were included for data extraction and synthesis. The prematurity proportions ranged from 1.8 to 33.6% by USG and varied from 3.4 to 16.5% by the LMP. The pooled risk difference of prematurity proportions revealed an overestimation of the preterm birth of 2% in favor of LMP, with low certainty: 0.02 (95%CI: 0.01 to 0.03); I2 97%). Subgroup analysis of USG biometry (eight articles) showed homogeneity for a null risk difference between prematurity proportions when crown-rump length was the reference: 0.00 (95%CI: -0.001 to 0.000; I2: 0%); for biparietal diameter, risk difference was 0.00 (95%CI: -0.001 to 0.000; I2: 41%). Only one report showed the SGA proportions of 32% by the USG and 38% by the LMP. Conclusions LMP-based GA, compared to a USG reference, has little or no effect on prematurity proportions considering the high heterogeneity among studies. Few data (one study) remained unclear the influence of such references on SGA proportions. Results reinforced the importance of qualified GA to mitigate the impact on perinatal statistics. Trial registration Registration number PROSPERO: CRD42020184646.

Gestational age assessed by optical skin reflection in low-birth-weight newborns: Applications in classification at birth

“…Improve counting of preterm births is a priority in planning and monitoring actions to achieve national Sustainable Development Goals ( 2 ). In a recent meta-analysis study, our group reported higher values in the proportion of preterm birth, ranging from 1% to 3% when the LMP is the reference compared to obstetric ultrasound until 24 weeks of gestation ( 43 ). This way, accessible and more accurate approaches are welcome to obtain a reliable GA at birth.…”

Intrauterine growth restriction, prematurity, and low birth weight: risk phenotypes of neonatal death, Rio de Janeiro State, Brazil

“…In the study of the Child Health Epidemiology Reference Group SGA - Preterm Birth Working Group, the prevalence of the low birth weight, preterm and SGA phenotype was 0.7% in Latin America, 1.6% in Africa, and 2.3% in Asia 27 . Regarding the methodological choices, the factors include different diagnostic approaches to gestational age 28 , different curves to assess the adequacy of weight for gestational age 22 , 29 , 30 , the type of basis of the study - population or hospital - the inclusion and exclusion criteria of newborns, especially at risk, such as twins and those with congenital malformations, who usually have higher frequencies of low weight, prematurity, and fetal growth restriction 31 , 32 , 33 . Notably, in Brazil, most deliveries occur in hospitals, which would be less relevant for national studies 15 .…”

“…After classification, live births were described according to maternal characteristics. Sociodemographic variables included age group (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) and ≥ 35 years old); skin color (white, black and brown), and schooling (0-3; 4-7 and ≥ 8 years of study). Parity was evaluated according to the number of previous deliveries (zero: primiparous and ≥ 1: multiparous).…”

Restrição do crescimento intrauterino, prematuridade e baixo peso ao nascer: fenótipos de risco de morte neonatal, Estado do Rio de Janeiro, Brasil

“…No estudo do Child Health Epidemiology Reference Group SGA -Preterm Birth Working Group, a prevalência do fenótipo baixo peso ao nascer, pré-termo e PIG foi de 0,7% na América Latina, 1,6% na África e 2,3% na Ásia 27 . Quanto às escolhas metodológicas, os fatores abrangem diferentes abordagens diagnósticas da idade gestacional 28 , diferentes curvas para avaliar adequação do peso para idade gestacional 22,29,30 , tipo de base do estudo -populacional ou hospitalar -, critérios de inclusão e exclusão dos recém-nascidos (principalmente de risco, como gemelares e aqueles portadores de malformações congênitas, que costumam apresentar mais frequentemente baixo peso, prematuridade e restrição do crescimento fetal) 31,32,33 . Deve ser lembrado que, no Brasil, a grande maioria dos partos ocorre em hospitais; portanto, este fator pesaria menos para estudos nacionais 15 .…”