Japan Ultrasound EFW Reference, 2025

When

The Japanese ultrasound fetal biometry reference was published in 2025 in Scientific Reports.

Who Developed It

The study was authored by Sumito Nagasaki, Keisuke Ishii, Yoshitaka Murakami, Anna Tsutsui, Nobuhiro Hidaka, Hironori Takahashi, Kiyotake Ichizuka, Kei Miyakoshi, Kiyonori Miura, Susumu Miyashita, Yoshimasa Kamei, Masahiko Nakata, and the Study Group on New Reference Values for Fetal Biometry in Japan.

Source: https://www.nature.com/articles/s41598-025-14508-9

Why This Source Is Credible

This source is credible because it was published in a peer-reviewed scientific journal, used a prospective research protocol, and was designed specifically to reassess fetal biometry reference values in Japan. The study describes the population, ultrasound measurements, estimated fetal weight formulas, and statistical method used to build gestational-age-specific values.

Its credibility is strongest for Japanese fetal biometry patterns because the study was designed around a Japan-specific population and measurement context.

Who Was Included

The study included singleton pregnancies receiving prenatal checkups at obstetric facilities across Japan. It was designed as a cross-sectional prospective study using a research-specific protocol to improve ultrasound data quality.

The authors state that the work was motivated by changes in Japanese birthweight trends, advances in ultrasound technology, and the need to reassess older Japanese fetal biometry charts.

Measurement Type

This source is based on ultrasound fetal biometric measurements and estimated fetal weight, not direct fetal weighing. Estimated fetal weight was calculated using both the Shinozuka formula and the Hadlock-3 formula.

Because different formulas can produce different estimated fetal weights, the formula context is part of how the percentile should be interpreted.

How It Was Built

During routine prenatal care, the study recorded ultrasound measurements including:

• biparietal diameter
• head circumference
• abdominal circumference
• femur length

Estimated fetal weight was calculated using both the Shinozuka formula, commonly used in Japan, and the Hadlock-3 formula, widely used internationally. The authors then developed gestational-age-specific reference values using best-fitted fractional polynomial regression.

What It Means

This source describes fetal ultrasound biometric measurements and estimated fetal weight patterns in a Japanese population.

The study found that fetal biometry values in the Japanese population were generally smaller than international standards and also smaller than values reported from other Asian references. This supports the idea that population-specific references can matter when assessing fetal size.

How To Interpret It

Use this source as a Japan-specific ultrasound reference. A percentile based on this source means the measurement is being compared with the Japanese study population at a similar gestational age.

It should not be interpreted as a general "Asian" reference. The authors specifically describe the Japanese population and compare it with international and other Asian studies.

What This Source Should Not Be Used For

This source should not be used by itself to diagnose fetal growth restriction, macrosomia, placental insufficiency, or pregnancy risk. It should also not be generalized to all Asian populations. It provides a Japan-specific reference comparison, and clinical interpretation requires gestational dating, ultrasound quality, growth trend, and medical context.

Limitations

• The source is population-specific to Japan and should not be generalized to every Asian or global population.
• The study used a cross-sectional design, meaning each pregnancy contributed one measurement for analysis rather than repeated longitudinal measurements across the full pregnancy.
• Estimated fetal weight depends on the formula used; Shinozuka and Hadlock-3 can produce different values.
• The findings are useful for reference comparison, not for diagnosis by themselves.
• Clinical interpretation still depends on measurement quality, gestational dating, interval growth, and medical context.

Bottom Line

The Japan 2025 reference is valuable because it is recent, prospective, and population-specific. Its main strength is relevance to Japanese fetal biometry patterns. Its main limitation is that it should not be generalized beyond the population and methods used to build it.