Chinese fetal biometry: reference equations and comparison with charts from other populations

Objective: This study aimed to construct new reference charts and equations for fetal biometry from Chinese fetuses at 15-40 weeks and to compare them with previous references. Method: This was a prospective, cross-sectional study of singleton pregnancies in patients with a confirmed gestational age who underwent ultrasound examinations between the 15th and 40th weeks of gestation. Each woman was selected only once for this study. Biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were recorded. For each measurement, separate regression models were fitted to estimate the mean and standard deviation at each menstrual age. Z-scores were calculated with our reference equations for comparison with other references. Results: New charts and reference equations involving 7553 Chinese women were created for BPD, HC, AC, and FL. Reference equations were cubic models. Prediction intervals for the new reference charts were similar to those of previous references, but with some slight differences. The main difference in our fetal biometric measurements compared with those of Korea and Hong Kong was the FL. Conclusions: We report new Chinese reference charts and equations for fetal biometry. These reference charts and equations are available for clinical use in obstetric ultrasound studies for the Chinese population.