NICHD Fetal Growth Study EFW Standards, 2015

When

The NICHD Fetal Growth Study racial and ethnic fetal growth standards were published in 2015 in the American Journal of Obstetrics and Gynecology.

Who Developed It

The study was conducted by investigators associated with the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies. The published article lists Germaine M. Buck Louis, Jagteshwar Grewal, Paul S. Albert, Anthony Sciscione, Deborah A. Wing, William A. Grobman, Roger B. Newman, Ronald Wapner, Mary E. D'Alton, Daniel Skupski, Michael P. Nageotte, Angela C. Ranzini, John Owen, Edward K. Chien, Sabrina Craigo, Mary L. Hediger, Sungduk Kim, Cuilin Zhang, and Katherine L. Grantz.

Source: https://doi.org/10.1016/j.ajog.2015.08.032

Why This Source Is Credible

This source is credible because it was published in a peer-reviewed obstetrics journal and came from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies. It used a prospective multicenter design, low-risk pregnancy screening, repeated ultrasound assessment, and documented statistical modeling.

Its credibility is especially strong for explaining why fetal growth references may differ across defined United States study groups.

Who Was Included

The study recruited 2,334 healthy women with low-risk singleton pregnancies from 12 community and perinatal centers in the United States between July 2009 and January 2013.

The cohort included four self-identified groups:

• non-Hispanic White
• non-Hispanic Black
• Hispanic
• Asian

Participants were screened early in pregnancy for health status and low-risk characteristics. The published abstract reports that 1,737 fetuses continued to meet the low-risk standard at birth and were included in the final standards.

Measurement Type

This source is based on ultrasound estimated fetal weight and fetal biometric measurements, not direct fetal weighing. Estimated fetal weight is calculated from ultrasound measurements, so values can vary with measurement quality, fetal position, equipment, and formula choice.

How It Was Built

Participants were followed prospectively with longitudinal fetal measurements. Women were assigned among four ultrasound schedules, and interviews, anthropometric assessments, and medical record abstraction were performed.

The researchers estimated group-specific fetal growth curves using linear mixed models with cubic splines. They calculated estimated fetal weight and biometric parameter percentiles for each gestational week.

What It Means

The NICHD standards show how estimated fetal weight differs across the four self-identified United States study groups. The study found statistically significant differences in estimated fetal weight after 20 weeks.

The study group labels describe the source population used to build each chart. They should not be read as a biological rule, an identity judgment, or a clinical instruction.

How To Interpret It

Use the NICHD source as a United States study-group-specific comparison. It can help explain why a single pooled chart may classify measurements differently across populations.

The percentile result means "relative to this NICHD study group at this gestational age." It does not mean that the selected study group is medically required for a specific user, and it does not diagnose a fetal growth condition.

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 not be used to assign personal identity or biological meaning to a person. The study-group labels describe how the source population was analyzed, and clinical interpretation requires broader medical context.

Limitations

• The source is based on United States study populations and may not apply to every country or mixed population context.
• The study-group labels are sensitive and should be explained as source labels, not personal identity categories.
• Estimated fetal weight is calculated from ultrasound measurements and is subject to measurement and formula error.
• The standards were designed from low-risk pregnancies, so they do not directly represent complicated pregnancies.
• Clinical interpretation requires context beyond percentile position.

Bottom Line

The NICHD Fetal Growth Study is valuable because it was prospective, multicenter, and designed to examine fetal growth differences across self-identified United States study groups. Its main limitation is that the group-specific charts require careful wording and should not be treated as automatic personal classification or diagnosis.