Selective Laser Photocoagulation

Introduction

Monochorionic twin gestations are at increased risk of perinatal morbidity and mortality related to a shared placental circulation. They are uniquely susceptible to the development of twin-twin transfusion syndrome (TTTS), with an incidence of approximately 10% to 15%. TTTS involves unbalanced shunting of blood between twins across vascular anastomoses within the placental bed. Without intervention, early-onset TTTS has a mortality rate that can approach 95%; among survivors, there is a substantial risk for profound neurologic handicap.

Fetoscopic selective laser photocoagulation (SLP) of anastomotic vessels has emerged as the most efficacious therapy to treat TTTS. SLP refers to intentional, laser-induced interruption of pathologic vascular communications linking donor and recipient circulations across a shared placental surface. By interrupting flow through these aberrant channels, the procedure directly disrupts a key component of the underlying disease process. In contrast, amnioreduction is an alternative therapy for TTTS that temporizes the condition indirectly by removing excess recipient twin amniotic fluid. Because amnioreduction addresses a consequence (polyhydramnios) of the disease state, but does not disrupt the underlying disease pathway itself, serial interventions are often required to support an affected pregnancy to an advanced gestational age.

SLP for treatment of TTTS involving laparotomy and direct uterine entry was first described by De Lia et al. in 1990. Advances in technique and technology since that first description permit minimally invasive percutaneous approaches. The procedure introduces custom-designed fetoscopic equipment with articulating eyepieces and fiber optic video displays under continuous ultrasound (US) guidance through percutaneous uterine access. Previously, the procedure involved nonselective photocoagulation of any vessels that crossed the division created by the insertion of the amniotic membrane onto the chorionic plate; however, at the present time, careful evaluation of the vascular equator between the twins targets photocoagulation of identified pathologic anastomoses. Available outcomes data suggest SLP is superior to amnioreduction with respect to survival, and survival free of severe neurologic injury, validating SLP as the optimal therapy for early-onset, severe TTTS ( Chapter 169 ).

Procedure