INTERGROWTH-21st Hadlock EFW Standard, 2020

When

The INTERGROWTH-21st Hadlock estimated fetal weight standard was published in 2020 in Ultrasound in Obstetrics & Gynecology. The broader INTERGROWTH-21st project was conducted between 2009 and 2014.

Who Developed It

The 2020 Hadlock estimated fetal weight update was authored by J. Stirnemann, L. J. Salomon, and A. T. Papageorghiou. It belongs to the INTERGROWTH-21st family of standards and tools.

Source: https://intergrowth21.com/tools-resources/fetal-growth

Why This Source Is Credible

This source is credible because it belongs to the INTERGROWTH-21st family of standards, which was built through a coordinated international research program with defined study sites, protocols, and quality-control procedures. The 2020 estimated fetal weight update was published in a peer-reviewed ultrasound journal and clearly states the formula used for the updated charts.

Its main credibility strength is methodological consistency: the reference is tied to a known international project and uses a specified Hadlock three-parameter estimated fetal weight method.

Who Was Included

The broader INTERGROWTH-21st project was a multi-centre, multi-ethnic, population-based project conducted in eight urban areas:

• Pelotas, Brazil
• Shunyi County, Beijing, China
• Central Nagpur, India
• Turin, Italy
• Parklands Suburb, Nairobi, Kenya
• Muscat, Oman
• Oxford, United Kingdom
• Seattle, United States

The project focused on growth, health, nutrition, and neurodevelopment from early pregnancy through early childhood. The fetal growth standards were built from carefully selected populations intended to support international prescriptive standards.

Measurement Type

This source is based on ultrasound estimated fetal weight, not direct fetal weighing. The 2020 charts use the Hadlock estimated fetal weight formula based on abdominal circumference, head circumference, and femur length.

Because estimated fetal weight is formula-based, the percentile result depends on both the ultrasound measurements and the selected formula.

How It Was Built

The 2020 estimated fetal weight charts updated the earlier EFW approach to use the Hadlock formula with three ultrasound parameters:

• abdominal circumference
• head circumference
• femur length

The INTERGROWTH-21st resource page states that the 2020 updated charts are the recommended INTERGROWTH-21st charts for estimated fetal weight.

What It Means

This standard compares an estimated fetal weight with an international INTERGROWTH-21st reference framework using the Hadlock three-parameter EFW formula.

The result is a percentile or z-score position within that reference. It describes relative size compared with the selected standard. It does not directly measure health, placental function, or future outcome.

How To Interpret It

Use this source as an international standard-based comparison. It is especially useful when a consistent global framework is desired.

Different standards may produce different percentile positions because they are built from different populations, formulas, gestational-age handling, and statistical approaches. A difference between INTERGROWTH-21st and another source should be treated as a reason to understand the source context, not as proof that one result is clinically wrong.

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 mixed or combined with other reference charts. It provides a standard-based comparison, and clinical interpretation requires gestational dating, ultrasound quality, growth trend, and medical context.

Limitations

• Estimated fetal weight depends on ultrasound measurement quality and formula choice.
• The 2020 update is formula-based and should be understood in relation to the underlying INTERGROWTH-21st fetal biometry standards.
• International prescriptive standards may not match every local population.
• Percentile position alone is not a diagnosis and should not be used without clinical context.
• The standard should not be mixed or combined with other charts; each reference should be interpreted separately.

Bottom Line

The INTERGROWTH-21st Hadlock EFW standard is a respected international comparison source. Its strength is a consistent multi-country framework and updated Hadlock-based EFW method. Its limitation is that a global standard may not capture every local population pattern or individual clinical situation.