On “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”

In a meta-analysis that assessed published mortality and morbidity rates in twins after fetoscopic placental laser surgery (FPLS) for twin-to-twin transfusion syndrome (TTTS), Rossi and D'Addario were troubled by the 40% of donors and 30% of recipients who died, as well as the 9% (range, 5 to 23%) and 10% (0.8 to 21%) cerebral injury rate in donors and recipients, respectively.[1] They propose that a first-trimester lethal or cerebral injury may occur before the FPLS (usually performed in the second trimester), and that efforts should be made toward first-trimester diagnosis and perhaps earlier intervention. Although theoretically possible, we believe that the mortality and cerebral injury following FPLS is less enigmatic and explained by factors not apparent in meta-analysis.

The nature of monochorionic (MC) placental factors renders 100% intact survival for both twins, even in the absence of TTTS, unlikely.[2] However, the actual or expected rate of intact infant survival in FPLS-treated TTTS has yet to be determined by rational means. We have maintained that the surgical objective of FPLS should be isolation of the fetal circulations because it is technically feasible and required to minimize MC twin mortality and morbidity.[3] This new reality for the twins begins when all the anastomoses within the vascular equator are ablated, but there are indications in the articles included in the meta-analysis that this is not always the case.

Patent anastomoses after FPLS can cause ongoing TTTS, reverse TTTS, acute intertwin exsanguination and death of both fetuses, acute intrapartum transfusion, anemia in a surviving co-twin after one fetal death with evidence of cerebral injury or other somatic tissue loss, or anemia-polycythemia at birth. We found two series of postpartum placental examination following FPLS in experienced centers, which reported residual anastomoses in 33% (17 of 52) at one[4] and 70% (7 of 10) in the other with a mean 2.4 ± 2.2 remaining anastomoses.[5]

The second variable not apparent in the meta-analysis is the presence of cervical insufficiency (CI) at the time of FPLS, which has been shown by Robyr et al to be a significant risk factor for premature delivery.[6] The mean cervical length for women delivering before 28 weeks was 32 mm, with a very poor prognosis at ≤20 mm. In their conclusions, they urged evaluation of methods that could prevent this prematurity from CI after FPLS, but in the 5 years since, rescue cerclage has become increasingly controversial. Nevertheless, we have screened for CI (defined as cervical length ≤30 mm with funneling) in the perioperative period and performed rescue cerclage in 15% of our FPLS cases.

Before undertaking first-trimester TTTS protocols, we suggest studies of FPLS to determined the actual rate of intact survival (as well as the incidence of other signs of patent anastomoses listed earlier) in the second trimester when the fetal circulations are isolated, compared with cases when they are not. For example, centers performing FPLS could submit a visual recording of the intrauterine events, outcome data, and the fresh postpartum placenta for evaluation by an unbiased reviewer and pathologist. Additional data for CI, with or without rescue cerclage (which becomes more difficult technically with worsening degrees of CI) could be gathered concurrently.

We are encouraged by the increasing acceptance of FPLS but feel committed to maximizing its efficacy and dealing with confounding factors for our patients. If the disappointing outcomes with second-trimester FPLS remain after closer scrutiny, then resources for studies proposed by the authors will be justified.

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 Gaziano E P, De Lia J E, Kuhlmann R S. Diamnionic monochorionic twin gestations: an overview.  J Matern Fetal Med. 2000;  9(2) 89-96
• 3 De Lia J E, Kuhlmann R S, Cruikshank D P, O'Bee L R. Current topic: placental surgery: a new frontier.  Placenta. 1993;  14(5) 477-485
• 4 De Paepe M E, Friedman R M, Poch M, Hansen K, Carr S R, Luks F I. Placental findings after laser ablation of communicating vessels in twin-to-twin transfusion syndrome.  Pediatr Dev Pathol. 2004;  7(2) 159-165
• 5 Lopriore E, Middeldorp J M, Oepkes D, Klumper F J, Walther F J, Vandenbussche F P. Residual anastomoses after fetoscopic laser surgery in twin-to-twin transfusion syndrome: frequency, associated risks and outcome.  Placenta. 2007;  28(2-3) 204-208
• 6 Robyr R, Boulvain M, Lewi L et al.. Cervical length as a prognostic factor for preterm delivery in twin-to-twin transfusion syndrome treated by fetoscopic laser coagulation of chorionic plate anastomoses.  Ultrasound Obstet Gynecol. 2005;  25(1) 37-41