Scientific Perspectives on Evaluating Fetal Physical Development Around Birth: Historical Approaches and Practices in Japan

Fetal growth assessment has been performed using ultrasound measurements and the estimated fetal weight (EFW) derived from them. The Shinozuka formula—a rational equation based on fetal volume and specific gravity—has served as the de facto standard, maintaining high accuracy across a wide range of gestational ages and independent of fetal body proportions. The reference values used to evaluate these measurements were established from a normal control survey population, representing fetuses developing under optimal conditions. As the distribution of these reference values has been confirmed to follow a normal distribution, measurements can be uniformly evaluated in relation to gestational age using standard deviations from the mean. This paper provides an overview of methods for fetal growth assessment, the theoretical basis of reference values, and the historical development and clinical application of fetal biometric evaluation in Japan.