Persistent elevation of cell-free fetal DNA levels in maternal plasma after selective laser coagulation of chorionic plate anastomoses in severe midgestational twin-twin transfusion syndrome

Objective

This study was undertaken to determine whether laser thermocoagulation for twin-twin transfusion syndrome (TTTS) causes increased cell-free fetal DNA levels in maternal plasma, potentially as a result of placental injury.

Study design

We enrolled 34 patients with twin pregnancies complicated by severe TTTS who underwent fetoscopic selective laser ablation of placental vascular anastomoses. Blood samples were drawn before and sequentially after the procedure. Fetal DNA in maternal plasma was quantified by polymerase chain reaction amplification of a Y-chromosome sequence.

Results

Compared with baseline, median elevations of fetal DNA levels were 0.8% at 30 minutes (P=.32), 15.8% at 60 minutes (P=.1), 179.5% at 24 hours (P=.003), and 172.9% at 48 hours (P=.003). Factors associated with increased fetal DNA levels at 24 hours after procedure included longer operation time, higher number of vessels ablated, and subsequent in utero fetal death (P=.01, .04, and .04, respectively).

Conclusions

Persistent elevation of fetal DNA levels in maternal plasma after laser ablation suggests that circulating fetal DNA could derive from placental injury. Plasma fetal DNA analysis may be an additional prognostic marker for fetal outcome after laser therapy.

Key words: Cell-free fetal DNA, Twin-twin transfusion syndrome, Fetoscopic laser ablation, Placental pathology, In utero fetal death