Methodological Quality of Studies Designed to Create Twin-Specific Neonatal Anthropometric Charts: A Systematic Review

Twin fetuses show a physiologically slower growth rate in the third trimester compared to singletons. Therefore, it has been suggested that the anthropometric evaluation of twins at birth should be performed using twin-specific charts. To be reliable, anthropometric charts need to fulfil certain methodological criteria to systematically review studies that have developed neonatal twin-specific anthropometric charts and assess their methodological quality. A comprehensive search was conducted across Cinahl, Embase, Global Index Medicus, PubMed, Scopus, Web of Science, Google Scholar, and relevant preprint repositories, followed by a predefined snowballing search. Two reviewers independently screened studies for eligibility, selecting those that have developed cross-sectional anthropometric charts for twins at birth, published since January 1990. Articles were excluded if they did not use anthropometric measurements at birth to construct charts. Two reviewers independently extracted data and performed quality assessment with a 16-item grading system. Sixty-eight studies were included, with all but one constructed reference, not standard, charts. Most studies did not meet the quality criteria: only 9% were prospectively designed, 34% reliably estimated gestational age, 19% reported standardized instruments, 28% described measurement techniques, and 26% did not stratify centiles by sex. This review reveals considerable methodological limitations in existing twin-specific neonatal anthropometric charts.