Fetal Growth Biometry Calculator

What is Fetal Biometry?

Fetal biometry is the measurement of your baby's body parts using ultrasound. These measurements help estimate how big your baby is and whether they are growing normally. The main measurements are:

• BPD (Biparietal Diameter): Width of the baby's head
• HC (Head Circumference): Measurement around the baby's head
• AC (Abdominal Circumference): Measurement around the baby's belly — the most important for growth
• FL (Femur Length): Length of the baby's thigh bone
• EFW (Estimated Fetal Weight): Calculated from the above measurements

What Do Percentiles Mean?

A percentile tells you how your baby's size compares to other babies at the same gestational age. For example, the 50th percentile means your baby is average size — half of babies are larger and half are smaller. The 10th percentile means your baby is smaller than 90% of babies at the same age.

What is FGR (Fetal Growth Restriction)?

FGR means the baby is not growing as expected, usually because the placenta is not providing enough nutrients and oxygen. It is diagnosed when the estimated weight is below the 10th percentile AND there are signs of placental insufficiency (such as abnormal Doppler blood flow). Babies with severe FGR (below the 3rd percentile) need close monitoring regardless of Doppler findings.

What is Doppler Monitoring?

Doppler ultrasound measures blood flow in two important blood vessels:

• Umbilical Artery (UA): The blood vessel in the umbilical cord carrying blood from baby to placenta. Abnormal flow means the placenta is working harder than normal.
• Middle Cerebral Artery (MCA): A blood vessel in the baby's brain. When the baby is under stress, more blood is sent to the brain — this is called "brain-sparing" and is a sign the baby needs closer monitoring.

Growth Standards Used

• INTERGROWTH-21st: International standard from healthy pregnancies in 8 countries worldwide — represents optimal fetal growth potential
• Hadlock (1991): The most widely used standard in U.S. clinical practice, derived from a North American population
• WHO (2017): World Health Organization standard from a large multinational study — similar to INTERGROWTH-21st but uses different methodology