When Is A Baby Too Small? Managing Third-trimester Fetal Growth ...

How is FGR diagnosed?

The diagnosis is based on ultrasound, and most centers use the 10th percentile cutoff to raise the alarm of possible fetal growth restriction. The next step is to have a discussion with the patient about her health history and her prior obstetrical history.

If a patient’s previous baby was less than 6 pounds at birth but was full-term and healthy, her current baby simply may be constitutionally small. If this is her first, or if previous babies were bigger, we will be more concerned about FGR. In either case, we will check the amniotic fluid and umbilical blood flow to help in the evaluation of placental function.

What happens next?

If the amniotic fluid and Doppler ultrasound are normal, we’ll watch the baby over the next few weeks and, if steady growth continues with no new concerns, that’s a good sign. The actual delivery timing will depend on how well the baby continues to grow and whether the amniotic fluid and the Doppler testing remain normal.

We generally recommend delivering the baby as close to the due date as possible to reduce the risk of needing long-term, specialized care after delivery. If the baby is:

• Between the 3rd and 10th percentiles for size, we try to get them to 38 weeks gestation.
• Smaller than the 3rd percentile, we try to get them to 37 weeks.

Often, our specialized team can safely get babies to 38 or 39 weeks before delivery, provided they have no other risk factors. Centers with less FGR management expertise tend to deliver earlier to avoid the risk of stillbirth. However, the earlier a baby arrives, the longer they typically stay in the neonatal intensive care unit (NICU).

Since the causes and severity of IUG can be so varied, your care plan will be customized based on your needs. Some patients are hospitalized for daily fetal heart rate monitoring. If you are hospitalized, we may recommend a complete course of steroids to help support fetal lung development before delivery.

If you end up needing early delivery, it does not mean an automatic cesarean section (C-section). Many babies are otherwise healthy except for being small, so it is likely safe to try vaginal delivery. Babies that are severely growth restricted or that have abnormal Doppler patterns may not do well with labor, so C-section may be indicated. A discussion with your doctor is always recommended.