Establishing twin birth weight percentile values with gestational age of 22 to 42 weeks in China: a synthesis study of curve modelling

A twin-based chart of birth weight was useful to avoid overdiagnosis of small for gestational age (SGA) or large for gestational age (LGA) in twins comparing to the singleton-based chart. Several twin-based charts of birth weight were reported based on large data from nationwide, multiple cities or local regions in China. However, these twin-based charts showed inconsistent ranges across gestational age (GA) and not well-consistent growth trajectories, and may require further integration. We aimed to develop a set of smoothed percentile growth curves of twin birth weight in Chinese neonates that allows for continuous use from extremely preterm to full-term. We collected twin birth weight data through a procedure of systematic review by searching PubMed, Scopus, Web of science, Chinese national knowledge infrastructure (CNKI), and Wanfang from their inception to April 30, 2025. Finally, five studies that met the inclusion criteria were included in this present study. We used a two-stage proportionally weighted approach to generate initial integrated percentile data of twin birth weight, and then employed polynomial regression equation and the LMS method to establish the P₃, P₁₀, P₂₅, P₅₀, P₇₅, P₉₀, and P₉₇ reference values of twin birth weight that allowed for continuous use from GA of 22 to 42 weeks in Chinese male and female twins. Our established twin-based growth curves illustrated a distinct pattern comparing to the singleton-based growth curves in China. In conclusion, our established twin-based birth weight percentile references could be preferred over the use of singleton references when diagnosing SGA or LGA in twin newborns or monitoring the growth of twin newborns in China.