Triplet gestations

Selective laser photocoagulation of communicating vessels in triplet gestations

Triplet or higher-order multiple gestations may also develop TTTS, provided that a monochorionic placentation exists. In the case of triplets, pregnancies may be either dichorionic or monochorionic. SLPCV in dichorionic triplets differs little from that of twins, other than the unaffected ‘singleton’ may interfere with trocar access to the amniotic cavity of the recipient twin. 

In monochorionic triplets, one of three combinations may exist: one recipient–two donors, one donor–two recipients, and one donor–one recipient–one unaffected. Because vascular anastomoses will typically be present between all three fetuses, a seemingly unaffected triplet may serve as a go-between fetus between the other two. 

The goal of SLPCV in all monochorionic triplets is to identify and photocoagulate all of the anastomoses present, even in the ‘–unaffected’ variety, to avoid persistent, reverse, or ‘de novo’ (in the case of –unaffected triplet) TTTS after surgery. Although some authors have suggested that all vascular anastomoses cannot be identified and photocoagulated in monochorionic triplets,24 this is not our experience. SLPCV in the one recipient–two donors variety is the simplest of the monochorionic triplets. 

The trocar is inserted into the amniotic cavity of the recipient twin and the anastomoses between the recipient and the two donors are identified. Anastomoses between the two donors are also easily seen, particularly if anhydramnios is present in the other two sacs. SLPCV in the case of one donor–two recipients is somewhat more difficult. If access to both recipients’ sacs is possible through separate incisions, the anastomoses between each recipient and the donor can be easily obliterated. 

The anastomoses between the two recipients may be more difficult to see, because of obstruction by the dividing membrane. A dual-camera approach may be necessary in these cases, correlating the images seen through each port. Alternatively, the dividing membrane between the recipients may be flattened against the placenta by performing a combined amnioinfusion of one recipient and amniodrainage of the other sac through a 2 mm port. 

This transforms the case into a pseudo one recipient–two donors variety, allowing visualization of the anastomoses through the dividing membrane. Laser photocoagulation through selective photothermolysis completes the surgery.