What is selective intrauterine growth restriction?

Selective intrauterine growth restriction (sIUGR) is a condition that can occur in some identical twin pregnancies. These pregnancies are known as monochorionic, which means the twins share a placenta (afterbirth) and a network of blood vessels. sIUGR happens when the placenta is not evenly apportioned between the twins. The placenta provides nourishment necessary for growth and development in the womb. Therefore, if an imbalance is present, one twin may become malnourished. sIUGR complicates 10 percent to 15 percent of monochorionic twin pregnancies.

Selective Intrauterine Growth Restriction Diagnosis

A maternal-fetal medicine specialist can diagnose sIUGR by studying the results of a detailed ultrasound. The first step in diagnosing sIUGR is verifying a monochorionic twin pregnancy. Then the fetal weight of each twin is assessed. The maternal-fetal medicine specialist must also rule out the possibility that twin-to-twin transfusion syndrome (TTTS) is causing the major weight discrepancy between the twins. When the estimated fetal weight of one twin is below the 10th percentile for gestational age, a diagnosis of sIUGR is confirmed.

Selective Intrauterine Growth Restriction Management and Treatment

A maternal-fetal medicine specialist may recommend several approaches to treating sIUGR, including:    

• Fetal monitoring: This management approach to sIUGR incorporates routine ultrasounds, fetal heart rate monitoring and examinations of fetal blood circulation (Doppler study) to evaluate fetal development. This helps physicians and families determine the optimal time for delivery.

• Fetoscopic laser ablation: This procedure involves the insertion of a small laparoscope (fetoscope) into the uterus. This allows the visual inspection of the placenta and enables the surgeon to seal the connecting blood vessels causing the nourishment imbalance. This procedure is typically only performed for the treatment of TTTS when there is co-existing sIUGR of the donor twin. Fetoscopic laser ablation is not a primary treatment for sIUGR because of the challenges related to the number and size of interconnected blood vessels between the twins.

• Cord occlusion: Sealing off the umbilical cord of the growth-restricted twin is a management option when its survival is unlikely and the co-twin is at risk of early delivery, organ damage or death.

• Blood transfusion following demise of the sIUGR twin: In situations where the growth-restricted twin dies, the co-twin may bleed out into the non-surviving twin through the interconnected blood vessels. Under these circumstances the surviving twin may lose a considerable amount of blood and develop anemia. When the time of likely death is known, emergency fetal blood transfusion of the anemic co-twin may be lifesaving.

Prognosis for Patients with Selective Intrauterine Growth Restriction

The outcome of sIUGR depends on two things:

• The degree to which the placenta imbalance has affected a baby’s development

• The stage in pregnancy when the mother delivers the baby