Current Environment:

What is selective fetal growth restriction (sFGR)?

Selective fetal growth restriction (sFGR) can occur in identical twins who share one placenta (monochorionic). It results in one of the twins growing slower and not as healthy as the other. sFGR is the second most common complication in monochorionic twins, occurring in about 15% of monochorionic twin pregnancies. Without fetal intervention, sFGR may result in risk to the healthier twin.

At Boston Children’s Hospital, our Maternal Fetal Care Center specializes in the evaluation and treatment of sFGR and other complex fetal conditions.

Selective Fetal Growth Restriction | Symptoms & Causes

What are the symptoms of sFGR?

sFGR doesn’t usually cause symptoms in a pregnant person. sFGR is diagnosed solely by fetal imaging methods, usually ultrasound.

What causes sFGR?

Monochorionic twins share one placenta, with each having its own section for receiving nutrients and oxygen. But in sFGR, how much placenta each twin gets may not be equal, resulting in one twin receiving more than the other. This can cause the smaller twin not to grow properly, which is known as growth restriction. In these cases, there are connections between the blood vessels of the twins, particularly in cases of growth restriction, which can change the blood flow patterns.

Pregnancies complicated by sFGR have chorionic vascular connections. Specifically, large artery-to-artery connections (anastomosis) may alter blood-flow patterns.

Selective Fetal Growth Restriction | Diagnosis & Treatments

How is sFGR diagnosed?

sFGR is usually diagnosed through an ultrasound. Doctors may also use Doppler to measure the blood flow between each fetus.

To determine sFGR, doctors look at the estimated weight of the smaller twin compared to the other twin, and the difference in weight between the twins. To be diagnosed with sFGR, the smaller twin must be below the 10th percentile for gestational age, and there must be a 25% or greater difference in weight between the twins.

Other tests may include:

How is sFGR treated?

Surgery isn’t needed for most cases of sFGR. Instead, doctors monitor the twins to ensure they’re doing OK. In cases where one twin grows slower and risks the health of the other twin, doctors will discuss performing one of the following:

  • Endoscopic laser surgery: A procedure where a small hole is made in the pregnant person’s abdomen, and a camera called an endoscope is used to look at the uterus. A laser is then used to stop the abnormal connections between twins and prevent any further harm to the healthier twin.
  • Selective reduction: A surgery done through a small hole in the pregnant person’s abdomen to prevent harm to the healthier twin when the other is severely compromised and risking the health of both.
  • Delivery: Doctors may deliver the twins and provide care in the NICU. The timing of delivery is decided on a case-by-case basis.

Because there are different ways to treat sFGR, the treatment doctors choose depends on the following factors:

  • when sFGR started in the pregnancy
  • the severity of the growth restriction
  • how the pregnant person wants to move forward

Selective Fetal Growth Restriction | Programs & Services