Illustration of fetal foot length measurement during sonography

Foot Length in Early Sonography: A New Perspective on Fetal Development

Mira Elwood in Health & Wellness November 2025 • 5 min read.

"Discover how fetal foot length measurements during early pregnancy sonography offer valuable insights into gestational age and potential developmental abnormalities."

For nearly a century, medical professionals have recognized the correlation between a baby's gestational age (GA) and the length of its foot (FT). Initial research, conducted almost a century ago, examined 704 fetal specimens and established this link. The insights gained from this early work continue to inform modern prenatal care.

Modern studies using ultrasound technology have continued to confirm this relationship in utero, in abortus, in stillborns, and in neonates to other measurements. Normograms, or standard growth charts, have been developed for the first trimester and later stages of pregnancy, allowing doctors to assess gestational age and monitor fetal development. The use of foot length in determining gestational age is an established practice.

However, there is limited information on the relationship between fetal foot length and other key fetal measurements in early pregnancy. This is particularly relevant when healthcare providers suspect abnormalities in early gestation. This article will explore the value of fetal foot length measurements in relation to other fetal measurements taken between 10 and 16 weeks of gestation, potentially offering a new, accessible approach to early prenatal assessment.

Why Fetal Foot Length Matters in Early Pregnancy Sonography

Illustration of fetal foot length measurement during sonography

A research study was conducted between March 7, 2014, and September 7, 2016, involving women attending routine obstetric appointments with normal pregnancies. Transabdominal ultrasound scans were performed utilizing advanced equipment (Accuvix V20 Prestige, Medison with a 4–8 MHz volumetric transducer or EPIQ 7, Philips with X6-1 matrix transducer). Key fetal measurements, including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and foot length (FT), were meticulously taken in millimeters. If the patient presented before completing 15 weeks of pregnancy, the crown rump length (CRL) was also measured.

The aim was to understand how foot length correlates with other measurements commonly taken during prenatal ultrasounds. Cases were excluded if the entire foot could not be clearly visualized, ensuring the accuracy of the data. The length of the fetal foot was measured as the longest distance from the most posterior point of the foot to the tip of the first or second toe, whichever was longer. Gestational age (GA) was calculated based on the last normal menstrual period or the first-trimester dating scan if there was more than a week's discrepancy.

Accurate Gestational Age Estimation: Fetal foot length provides a reliable estimate of gestational age in early pregnancy, comparable to traditional methods like crown rump length.
Early Detection of Abnormalities: Deviations in the expected foot length-to-other measurement ratios can signal potential skeletal dysplasias or chromosomal abnormalities.
Improved Diagnostic Accuracy: Combining foot length measurements with other fetal biometrics enhances the overall accuracy of gestational age assessment.
Non-Invasive Assessment: Ultrasound measurement of fetal foot length is a non-invasive procedure, posing minimal risk to the mother and fetus.

The results indicated a strong correlation between fetal foot length and various other fetal measurements, including biparietal diameter, head circumference, abdominal circumference, and femur length. Compared to crown rump length, the correlation between foot length and these other measurements was notably stronger. The femur length to foot length ratio and the femur length to abdominal circumference ratio both increased with gestational age, showing an inverse relationship throughout the study period.

The Future of Fetal Foot Length in Prenatal Care

The study concludes that fetal foot length is a valuable and accurate parameter for estimating gestational age during early pregnancy. Integrating foot length measurements with other standard fetal biometrics can improve the reliability of prenatal assessments. Awareness of the gestational age-dependent nature of fetal measurement ratios is crucial for accurate detection of potential fetal abnormalities. Further research with larger sample sizes is needed to confirm these findings and refine the application of fetal foot length in prenatal diagnostics.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.2147/ijwh.s122586, Alternate LINK

Title: A Revisit Of The Fetal Foot Length And Fetal Measurements In Early Pregnancy Sonography

Subject: Maternity and Midwifery

Journal: International Journal of Women's Health

Publisher: Informa UK Limited

Authors: Hong Soo Wong

Published: 2017-04-01

Everything You Need To Know

What is fetal foot length and why is it measured in early pregnancy sonography?

Fetal foot length is a measurement taken during early pregnancy sonography to estimate gestational age. It is measured as the longest distance from the most posterior point of the foot to the tip of the first or second toe, whichever is longer. Its utility lies in its ability to provide a reliable estimate of gestational age and, when combined with other fetal biometrics, enhances overall accuracy. The limited information on the relationship between fetal foot length and other key fetal measurements in early pregnancy highlights the need of new approaches to early prenatal assessment.

Besides foot length, what other measurements are typically taken during prenatal ultrasounds, and what equipment is used?

Healthcare providers measure biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and foot length (FT). Before 15 weeks of pregnancy, the crown rump length (CRL) is also measured. These measurements are taken during transabdominal ultrasound scans using advanced equipment such as Accuvix V20 Prestige or EPIQ 7. These measurements help in assessing fetal development and detecting potential abnormalities.

How can fetal foot length measurements assist in detecting potential fetal abnormalities during early pregnancy?

Fetal foot length can aid in the early detection of abnormalities because deviations in the expected foot length-to-other measurement ratios may indicate potential skeletal dysplasias or chromosomal abnormalities. This is particularly important when combined with other fetal measurements like biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). Awareness of the gestational age-dependent nature of fetal measurement ratios is crucial for accurate detection of potential fetal abnormalities.

What correlations were found between fetal foot length and other fetal measurements in the research study?

The study revealed a strong correlation between fetal foot length and other fetal measurements such as biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). Notably, the correlation between foot length and these measurements was stronger compared to crown rump length (CRL). The femur length to foot length ratio and the femur length to abdominal circumference ratio both increased with gestational age, demonstrating an inverse relationship throughout the study period. These findings supports the integration of foot length measurements with other standard fetal biometrics to enhance the reliability of prenatal assessments.

Are there any limitations to using fetal foot length as a measurement, and how can it be improved with other factors to determine gestational age?

While fetal foot length (FT) is valuable, relying solely on it has limitations. To get a more complete assessment of gestational age (GA) and fetal well-being, it should be used in conjunction with other fetal biometrics such as biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and, when applicable, crown rump length (CRL). Further research with larger sample sizes is needed to confirm and refine the application of fetal foot length in prenatal diagnostics, to ensure accurate detection of potential fetal abnormalities. Additionally, clinical context and maternal factors should be considered for a comprehensive evaluation.