Development of birth weight for gestational age charts and comparison with currently used charts: defining growth in the Polish population

Objectives: This study aimed to obtain the reference curves of birth weight for gestational age percentiles for the Polish population and to compare them to published charts in terms of detected proportions of small for gestational age (SGA) and large for gestational age (LGA). Methods: The reference curves of birth weight from 24 to 42?weeks of gestation were computed based on 39,092 singleton deliveries. The nomograms included the 3rd to the 97th percentiles and standard deviations. The percentiles were calculated for female and male newborns. The theoretical and true proportions of percentiles for the studied population were estimated based on six growth charts (Fenton, Intergrowth Project, global reference chart, Yudkin, Dubiel, and the World Health Organization chart). Results: The 50th percentile male and female newborns at 40?weeks weighed 3645.8 and 3486.7?g, respectively. The difference was 159.1?g. The ranges between the 3rd and 97th percentile at 40?weeks were 1481.5?g for males and 1423.5 for females. A total of 9.8% SGA and 10.27% LGA were defined, higher than that identified using the Fenton chart and even higher than that identified using the Intergrowth Project. Conclusion: Population growth charts identify more newborns with abnormal growth (both LGA and SGA). The similarity between charts in LGA above the 95th percentile is observed. The discrepancies in SGA are significantly greater, specifically in preterm births than in term births. Similar coverage is found in term pregnancies, regardless of birth weight for gestational age or intrauterine charts. The feasibility of a Polish population growth chart needs to be validated for predicting adverse perinatal outcomes.