Response to Letter to the Editor Regarding “Comparison of Donor and Recipient Outcomes Following Laser Therapy Performed for Twin-Twin Transfusion Syndrome: A Meta-Analysis and Review of Literature. Am J Perinatol 2009;26(1):27–32”

I thank Drs. De Lia and Worthington for their interest in my article[1] and the editors of the American Journal of Perinatology for the opportunity to reply.

I did not state that survival rate in monochorionic twins is 100% for both twins. However, untreated cases of twin-twin transfusion syndrome (TTTS) are associated with ~100% risk of fetal demise,[2] whereas the prognosis of monochorionic twins without TTTS is not as poor. This indicates that factors specific to the syndrome are responsible for the adverse outcomes.

I believe that the analysis of neonatal morbidity and mortality in TTTS should distinguish whether adverse outcomes are related to pathological factors, such as placental territory, stage at presentation, and number and direction of anastomoses versus other factors, such as prematurity and premature rupture of membranes. This was not the aim of my review. The isolation of the fetal circulations by laser therapy is surely useful to minimize the mortality and morbidity of monochorionic twins, and, as I stated in a previous review,[3] it should be considered the optimal treatment for TTTS. Once again, the treatments options for TTTS were not the aim of my review.

Although few of the included studies indicate that patent anastomoses may persist after laser therapy, they did not report whether there was an association between patent anastomoses and survival rates. Thus I could not analyze this factor as a confounding variable. In my experience, when residual anastomoses are present and still functional, signs of TTTS reappear and a second laser therapy can be safely performed without additional complications for the mother and infants. Cervical insufficiency is a frequent complication of twin pregnancies but is not specific to TTTS. As already mentioned, the articles included in my meta-analysis did not stratify survival rate for cervical insufficiency. Cervical factors and prematurity affect both donors and recipients; therefore analyzing them would have not contributed much to the review that was planned to distinguish donors from recipients.

I agree that further studies are needed to determine the actual rate of survival following laser therapy, but wide evidence indicates that laser therapy is the optimal method for TTTS. I fear that the aim of my article was misunderstood. The intent was not to analyze outcomes following laser therapy as I have previously published about it.[3] [4] The goal was to determine whether both twins benefit similarly from laser therapy. The conclusion of my meta-analysis does not indicate that outcomes with second-trimester laser therapy are disappointing. It simply indicates that in some cases TTTS may develop earlier than when it is actually diagnosed. If the diagnosis and treatment of TTTS can be anticipated, it could be expected that outcomes following laser therapy may be improved. In other words, what I propose is not a revision of the therapy but a revision of the diagnostic criteria.

REFERENCES

• 1 Rossi A C, D'Addario V. Comparison of donor and recipient outcomes following laser therapy performed for twin-twin transfusion syndrome: a meta-analysis and review of literature.  Am J Perinatol. 2009;  26(1) 27-32
• 2 Ville Y, Hecher K, Gagnon A, Sebire N, Hyett J, Nicolaides K. Endoscopic laser coagulation in the management of severe twin-to-twin transfusion syndrome.  Br J Obstet Gynaecol. 1998;  105(4) 446-453
• 3 Rossi A C, D'Addario V. Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of literature.  Am J Obstet Gynecol. 2008;  198(2) 147-152
• 4 Rossi A C, D'Addario V. Umbilical cord occlusion for selective feticide in complicated monochorionic twins: a systematic review of literature.  Am J Obstet Gynecol. 2009;  200(2) 123-129