Fetal Macrosomia

Your healthcare provider may order an ultrasound to check the fetal weight and amount of amniotic fluid. An ultrasound is a diagnostic procedure that transmits high-frequency sound waves through body tissues. These waves transform into video or photographic images.

Ultrasound can only estimate a fetus’s weight within about 10%. For instance, if the ultrasound estimates your baby is 9 pounds, that’s the “best guess.” But your baby could actually weigh somewhere between 8 pounds and 10 pounds.

As ultrasound isn’t precise and can’t predict shoulder dystocia, your healthcare provider will combine information from your ultrasound with your pregnancy history and physical exam to determine the safest timing and route of delivery.

To determine if you need an ultrasound exam, your healthcare provider will:

• Measure your fundal height (the distance from the top of your uterus to your pubic bone).
• Feel your belly. Your healthcare provider may press your abdomen in certain areas to judge the size of the fetus.

If your tests indicate the fetus is big, your prenatal care provider may suggest further testing to monitor fetal health. This could involve a biophysical profile or a nonstress test.