Is fetal weight ultrasound accurate?

The article was professionally consulted by BSCK II Pham Thi Tuyet Mai - Department of Obstetrics and Gynecology - Vinmec Hai Phong International General Hospital.

Ultrasound has important effects, especially for monitoring the fetal development status, which are:
Knowing gestational age and predicting delivery date Fetal status: Length, weight of the fetus as well as Important indicators such as: biparietal diameter, abdominal circumference, femur length, head circumference, abdominal diameter Detecting fetal abnormalities. Diagnosis of chromosomal syndromes or morphological abnormalities.

There are more than 30 different algorithms used to predict the baby's weight through the form of ultrasound. Parameters will be collected from different locations and used to calculate the baby's size. When the baby has too much weight and size, it will make the birth process often difficult.
The first danger of vaginal delivery of a very large baby is shoulder dystocia. This condition occurs when a baby's body becomes trapped in the mother's uterus and can damage certain nerves in the baby's arms and shoulders. This condition can cause permanent damage to the baby's hand muscles, as well as damage to the mother's pelvis.
If the fetus is found to be too large, the doctor will appoint a cesarean section to ensure the safety of mother and baby.


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Ultrasound is an inaccurate method of determining fetal weight. This method only helps to predict the baby's weight with an error of 8-15%, which means your baby may be 8-15% heavier or lighter than his actual weight.

Ultrasound is often more accurate when determining your baby's size during the first half of pregnancy. In the later stages, each fetus develops in a different way and the accuracy of the ultrasound now depends a lot on whether your baby is medium or small.
The closer to the due date, the bigger the baby grows and the doctors have a lot of difficulty determining the exact weight of the baby. During the third trimester of pregnancy, especially the period before labor, you will be asked to have regular ultrasounds. Some things the doctor wants to look at through the ultrasound results:
Position of the baby Place of the placenta Amniotic volume Volume Biophysics: This is done to look at the movement status, respiratory movement fetal respiration and muscle tone. Even if your baby is larger than normal, you can still have a normal delivery without a cesarean section. Predicted weight is just one factor that helps doctors consider choosing the most suitable delivery method and avoid risks for mother and baby.

Fetal weight ultrasound is not absolutely accurate, but this method is still widely used because of its convenience and ease of implementation. Performing an ultrasound method helps the doctor estimate and give more in-depth exploration when seeing abnormalities in the baby's weight.
Currently, Vinmec International General Hospital provides mothers with a comprehensive maternity care program with various pregnancy weeks: 12 weeks, 27 weeks, 36 weeks and labor packages. When you join the early pregnancy package, you will have many additional benefits.
Pregnant women will have regular visits with an Obstetrician, perform routine tests and ultrasounds to monitor the baby's development. Early detection of risks and complications for interventional treatment plans, minimizing adverse effects on mother and baby health. In addition, during pregnancy, pregnant women will also attend antenatal classes organized by the hospital to equip themselves with knowledge to help ease labor and prepare for the journey of motherhood. Dr. Tuyet Mai has over 30 years of experience in examination and treatment in the field of Obstetrics and Gynecology, especially in lower-line surgery, family planning, specialized laparoscopic surgery, and handling many severe surgeries. and difficult such as:
Hysterectomy, hymenectomy Surgery for uterine fibroids, cervical cancer Cervical cancer vaccination Cervical cancer early detection Cervical electrocautery Examination and treatment Endocrine

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