Diagnosis
Fetal macrosomia can't be definitively diagnosed until after a baby is born and weighed.
But if you have risk factors for fetal macrosomia, your healthcare professional likely will use tests to monitor your pregnancy. They may include the following tests.
Ultrasound
Toward the end of the third trimester, you may have an ultrasound. During that test, parts of the fetus's body are measured, such as the head, belly and legs. Those measurements can be used to estimate fetal weight. But the accuracy of ultrasound for predicting fetal macrosomia is not always reliable.
Ongoing tests during pregnancy
If fetal macrosomia is suspected due to a health condition in a pregnant person, such as diabetes, several tests may be recommended throughout pregnancy to watch a fetus's health. This is called antenatal testing. These tests typically aren't done when only fetal macrosomia is suspected, and there are no other health concerns.
The tests may include:
- Nonstress test. A nonstress test measures how fetal heart rate changes in response to a fetus's movements.
- Fetal biophysical profile. A fetal biophysical profile combines a nonstress test with ultrasound. It checks a fetus's movement and breathing, as well as the amount of amniotic fluid.
If there's a risk of fetal macrosomia, it can be helpful to talk with a doctor who specializes in caring for children, called a pediatrician, who has expertise in treating babies with fetal macrosomia.
Treatment
Even when a fetus is large, vaginal delivery may be possible. Before labor begins, talk with your healthcare professional about your options as well as risks and benefits.
Triggering uterine contractions with medicine before labor begins on its own, called inducing labor, typically isn't advised for fetal microsomia unless there are other health conditions that make inducing labor necessary. Research suggests that labor induction doesn't lower the risk of health concerns linked to fetal macrosomia.
A C-section might be recommended in the following situations:
- A pregnant person has diabetes, and a fetus is estimated to weigh 9 pounds, 15 ounces (4,500 grams) or more.
- A pregnant person doesn't have diabetes, and a fetus is estimated to weigh 11 pounds (5,000 grams) or more.
- A pregnant person has delivered a baby whose shoulder got stuck behind the pelvic bone in an earlier pregnancy. That condition is called shoulder dystocia.
If your healthcare professional suggests a C-section, make sure you understand the risks and benefits.
After a baby with fetal macrosomia is born, the baby likely will be examined for:
- Signs of birth injuries.
- Low blood sugar, called hypoglycemia.
- A blood condition that results in a high red blood cell count, called polycythemia.
The baby might need special care in a neonatal intensive care unit.
A baby with fetal microsomia may be at risk of childhood obesity and diabetes. Talk with your baby's healthcare professional about regularly checking for those conditions as the child grows.
If you give birth to a baby with fetal macrosomia and you haven't been diagnosed with diabetes before, you may be tested for diabetes. During future pregnancies, it's likely you'll be watched closely for symptoms of gestational diabetes. That's a type of diabetes that develops during pregnancy.
Coping and support
If your healthcare professional suspects fetal macrosomia during your pregnancy, you might feel anxious and worried.
Talk with your healthcare professional about what you can do to ease stress and promote a healthy pregnancy. You also may want to talk with others who've had babies with fetal macrosomia. Ask a member of your healthcare team about support groups and other resources that may be available in your area or online.
Preparing for your appointment
If you have risk factors for fetal macrosomia, the topic is likely to come up during your prenatal appointments.
Below are some questions to ask your healthcare professional about fetal macrosomia:
- What is the likely cause of the condition?
- What tests do I need?
- What needs to be done now?
- Do I need to follow any restrictions?
- How will fetal macrosomia affect my baby?
- Will I need to have a C-section?
- Will my baby need tests or special care after delivery?
If you think of other questions during the appointment, be sure to ask them too.
