Automated Fetal Weight Estimation: A Multicenter Validation Using Fractional Limb Volume

Ultrasound has been used for over 20 years to estimate fetal weight prior to birth. Sometimes this estimation is not always similar to what the baby actually weighs. In addition to the regular measurements taken at routine ultrasound exams, 3D ultrasound of the baby's arm and leg soft tissue may give us more precise information on how much the baby weighs. This measurement is called fractional limb volume. Fractional limb volume (FLV) is a soft tissue measurement of the arm or thigh that can be used to evaluate body composition. This measurement mostly reflects the fat and muscle development with a small amount of bone.

The recent introduction of 5D Limb Volume software (Samsung, Seoul, Korea) now makes it possible to efficiently and reproducibly measure semi-automated FLV using a computer guided technique.

Subjects will receive one ultrasound scan 4-7 days before their delivery. Both 2D and 3D measurements will be taken. These measurements will then be used to estimate fetal weight. We will compare estimated weight to actual birth weight in order to determine the accuracy and precision of the 5D Limb Volume technology. This data may also be used to develop new weight estimation models that could provide better accuracy and/or precision than what is currently provided using published methods.

Inclusion criteria

• Pregnant women (28-42 weeks) within 4-7 days of delivery
• Planned delivery at the collaborating hospital where the fetal US scan was performed
• Body mass index at first official prenatal appointment below 35.0 kg/M2
• Firm US dating criteria (early crown-rump length < 14 weeks gestational age)

Exclusion criteria

• Presence of technical factors (e.g. obesity) that make it difficult to visualize fetal structures
• Oligohydramnios determined by amniotic fluid index less than 5cm
• Fetal distress or unstable maternal condition
• Structural or chromosomal fetal anomalies