Fetal acceleration time/ejection time ratio for predicting neonatal respiratory distress syndrome. Systematic review

Luis A. Verde-Aguilera, Department of Gynecology and Obstetrics, Hospital de la Mujer Zacatecana, Zacatecas, Mexico
Natalia de J. Medina-Llamas, Department of Gynecology and Obstetrics, Hospital de la Mujer Zacatecana, Zacatecas, Mexico
Sergio A. Covarrubias-Cornelio, Department of Gynecology and Obstetrics, Hospital de la Mujer Zacatecana, Zacatecas, Mexico
Horacio Orozco-Flores, Department of Maternal-Fetal Medicine, Hospital General de Zona 1, Instituto Mexicano del Seguro Social (IMSS). Zacatecas, Mexico

Assessing fetal lung maturity minimizes neonatal respiratory distress syndrome (NRDS) in preterm births. Given the risks of amniocentesis, the pulmonary artery acceleration time/ejection time (At/Et) ratio emerges as a non-invasive ultrasonographic predictor, though lacking standard consensus. The objective was to determine the diagnostic accuracy of the At/Et ratio in predicting NRDS. Registered in PROSPERO (CRD420261324928; Preferred Reporting Items for Systematic Reviews and Meta-Analyses), PubMed, Cochrane Central Register of Controlled Trials, and Latin American and Caribbean Health Sciences Literature were searched. Studies evaluating the At/Et ratio against clinical NRDS diagnosis were included in the study. Quality was assessed using quality assessment of diagnostic accuracy studies-2, and a bivariate random-effects model provided pooled estimates. Five validation cohorts (1,058 fetuses; 152 NRDS cases) met the criteria. Pooled sensitivity was 82.2% (95% confidence interval [CI]: 73.6-88.4%) and pooled specificity was 86.3% (95% CI: 74.4-93.2%). All included studies showed a high risk of bias in the index test due to retrospective cut-off determination. In conclusion, the At/Et ratio is a non-invasive tool with strong sensitivity and specificity. However, clinical implementation is hindered by methodological biases and physiological contradictions regarding the predictive threshold direction. It should be used cautiously as an adjunct test until a standardized cut-off is prospectively validated.

Keywords: Fetal lung maturity. Pulmonary artery Doppler. Neonatal respiratory distress syndrome. Systematic review. At/Et ratio.