What is Hadlock Measurement?

The Hadlock measurement is a widely used method in obstetrics for estimating fetal growth and gestational age through ultrasound measurements. Developed by Dr. Frank Hadlock, this technique involves calculating fetal size based on a combination of parameters, such as biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). By applying these measurements in specific formulas, healthcare providers can assess the estimated fetal weight (EFW) and track how a baby grows throughout pregnancy.

Why Is Hadlock Measurement Important?

Hadlock measurements play a critical role in monitoring fetal health and development. They help ensure the baby is growing at a healthy rate, identify potential complications such as intrauterine growth restriction (IUGR) or macrosomia, and guide medical decisions about the timing of delivery or additional interventions. This method is especially valuable because it provides a non-invasive, reliable estimate of fetal size and weight, which is essential for managing pregnancies at risk of complications.

Key Points About the Hadlock Measurement

1. Accuracy and Standardization: The Hadlock method is considered the gold standard for estimating fetal weight and size due to its accuracy and widespread validation in clinical practice.
2. Multidimensional Approach: By combining several fetal measurements, it accounts for individual variability, offering a comprehensive picture of fetal growth.
3. Utility in High-Risk Pregnancies: It is particularly useful in pregnancies where growth abnormalities are suspected, enabling early detection and management of potential issues.

How big should your baby be now?

This chart outlines expected ultrasound measurements (in mm) based on gestational age.

BPD: biparietal diameter (the diameter between the 2 sides of the head
HC: head circumference
AC: abdominal circumference
FL: femur length

References:

Hadlock Formulas: Haddlock Radiology 1984; 152: 497-501

Hadlock FP, Harrist RB, Sharman RS, Deter RL, Park SK. "Estimating fetal age: Computer-assisted analysis of multiple fetal growth parameters." Radiology. 1984.

American Institute of Ultrasound in Medicine (AIUM). "Guidelines for ultrasound in pregnancy."