We read with interest the review article of the Society for Maternal-Fetal Medicine (SMFM) on twin-twin transfusion syndrome (TTTS). A salient conclusion of the article is that, “Fetoscopic laser photocoagulation of placental anastomoses is considered by most experts to be the best available approach for stages II, III and IV TTTS in continuing pregnancies <26 weeks, but the metaanalysis data show no significant survival benefit….” We would agree with this conclusion, provided that the statement is qualified as follows: “…but the metaanalysis data show no significant survival benefit, due to the inclusion of a flawed study in the metaanalysis.” The inclusion of bad studies is a known problem in metaanalyses. Indeed, the inclusion of the National Institutes of Health (NIH)-sponsored trial in the metaanalysis quoted by the SMFM authors exerts an unduly negative effect size in survival. This trial required a “test” amniocentesis prior to laser and the average experience with laser surgery prior to the trial at each of 3 participating centers was only 12 cases. The trial was stopped early due to a higher than expected perinatal loss rate in recipient twins treated with laser, where only 12.5% of stage III-IV recipients survived. Our group has suggested that the NIH study not be used for patient counseling, and consequently, not in metaanalyses, because of methodological reasons. Even centers that participated in the NIH study doubt the validity of the study, and therefore continue to offer laser surgery for TTTS.

A Cochrane metaanalysis, not cited in the SMFM article, in which the NIH trial was not included, showed that laser surgery resulted in less death of both infants per pregnancy, fewer neonatal deaths, and fewer perinatal deaths. In addition, the SMFM review paper did not cite the 2011 article with 682 TTTS patients treated with laser, the largest series to date, although this article met the inclusion criteria of the SMFM article and was published in the journal. In that paper, we reported an overall recipient survival rate after laser surgery of 84% (571/680) and 82% (319/391) for recipients in stage III and IV, a 90.3% rate of at least 1 survivor, and an overall perinatal survival rate of 78%. If one includes this study in Table 7 of the SMFM paper, instead of the 2007 article, the total number of available pregnancies for analysis would increase by 43% to 1553 (1008 – 137 + 682), with at least 1 survivor of 84% (1308/1553) and an overall perinatal survival of 70% (2156/3106). Therefore, with the above caveats, the data do show that laser surgery for TTTS provides significant survival benefit.