How is fetal macrosomia diagnosed?

During a pregnancy, it’s difficult to know how large the baby will be when he or she is born. Doctors use ultrasound tests to learn what they can about a fetus, including its size. An ultrasound is a diagnostic procedure that transmits high-frequency sound waves through body tissues. The echoes are recorded and transformed into video or photographic images of the internal structures of the body.

To diagnose fetal macrosomia, the doctor will look for:

  • The mother’s fundal height (the distance from the top of the uterus to the pubic bone)
  • The amount of amniotic fluid, which surrounds the baby inside the womb. If there is an abnormally large amount of amniotic fluid (polyhydramnios), the baby may be larger than average
  • The estimated weight of the baby based on ultrasound calculations

The doctor might also ask a parous mother (a woman who has given birth before) how much she thinks the baby weighs.

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