What is Selective Intrauterine Growth Restriction (SIUGR)?
Approximately 10% of monochorionic twins (or identical twins that share a placenta) encounter problems because the common placenta is not shared evenly. Sometimes, the distribution is so discrepant, that one twin is not getting enough nourshiment from the placenta. This results in poor growth in that twin, or selective growth restriction. The presence of a single placenta in a twin pregnancy signals that the twins are linked by common blood vessels. SIUGR is often initially confused with Twin to Twin Transfusion Syndrome (TTTS), but differs in that only one twin is affected. To complicate matters, some pregnancies can be affected by both TTTS and SIUGR.
The issue of SIUGR is worrisome for both the baby with the growth restriction, as spontaneous death can occur in as high as 40% of cases but also for the healthy co-twin because of the shared connections on the placenta. If the baby affected by SIUGR should pass away, the sudden drop in blood pressure may prompt the previously healthy baby to shift blood flow to its twin through the shared connections on the placenta. This hemorrhage of blood may lead to significant brain damage or death of the co-twin.
How is it diagnosed?
The diagnosis of SIUGR is established by ultrasound when the following characteristics are identified:
- single placenta
- estimated fetal weight (EFW) of one twin measures < 10th percentile for the assigned gestational age
- persistent absent or reversed flow in the umbilical artery of the growth restricted twin
How can SIUGR be treated?
Expectant Management: Expectant managment is the traditional treatment of pregancies affected by SIUGR. However, with the advent of other treatment options, the recommendations for follow up have increased dramatically. Each situation is unique, and warrants an individual assessment and care plan. The general recommendation is at least weekly ultrasounds, including doppler studies of the umbilical artery and fetal growth bi-monthly. Usually once patients reach viability- or the point at which an emergency cesarean section would be a reasonable option (typically as early as 24 weeks, and as late as 27 weeks), hospitalization is recommended for increased fetal surveillance. Delivery is indicated by poor ultrasound findings, or non-reassuring fetal heart rate tracings.
Cord Coagulation or Selective Termination: In cases of severe SIUGR, where the growth restricted baby's death is imminent (in pregnancies prior to 24 weeks), patients may opt to selectively terminate, or coagulate the cord of the growth restricted baby. While this is a difficult decision for families, it can be the right decision for certain situations. This can maximize the optimal outcome for the unaffected twin by eliminating the risk of death or brain damage from a spontaneous demise as well as severe preterm delivery for fetal distress of the growth restricted twin.
Cord coagulation is a minimally invasive procedure, in which a needle is guided by ultrasound into the umbilical cord and the blood flow is coagulated either by radiofrquency ablation or bipolar cautery. This interrupts the blood communication between the fetuses, and allows the remaining twin to progress as a singleton,without the complications from a sponatenous death. The demised baby remains in the amniotic cavity and to a certain degree, will begin to be reabsorbed.
Laser Photocoagulation: This surgical option utilizes the same technique as Laser Photocoagulation for TTTS (see above), with a different goal in mind. This procedure is recommended only in severe cases of SIUGR, as there are risks to the procedure. The goal of the procedure is to separate the circulations on the shared placenta so that in the event of a spontaneous demise, there would be no harm to the surviving twin. This procedure utilizes a small camera (fetoscope) to visualize the surface of the placenta. The communicating vessels on the surface of the placenta are identified, and sealed with laser energy. This procedure would be recommended only prior to 26 weeks of pregnancy.