When does “may be safer” become “safe?”

Ms Rao and colleagues have analyzed 1 accurate sentence in our article on dichorionic reductions of twins to singletons that monochorionic (MC) reductions have higher complications. 1 Evans MI Curtis J Evans SM Britt DW. Fetal reduction and twins. Am J Obstet Gynecol MFM. 2022; 4100521 Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar This special issue of the American the Journal of Obstetrics & Gynecology MFM devoted to twins has 2 other articles focusing on MC twins, so we did not comment on the articles that Rao and colleagues cited. However, the overall context must be considered before (1) concluding from 14 cases on radiofrequency ablation (RFA) reduction that such procedures are “safe” and (2) justifying dichotomizing what is an incremental continuum of fetal pathology between none and significant. Our publications and others suggested an approximately 10% risk of both loss and neurologic impairment after RFA. 2 Gebb J Dar P Rosner M Evans MI. Long-term neurologic outcomes after common fetal interventions. Am J Obstet Gynecol. 2015; 212 (e1–9): 527 Abstract Full Text Full Text PDF Scopus (17) Google Scholar Even a chi-square test comparing the ratios of 14:0 vs 12:2 (14% complication rate) would not be significant (X2=2.33; P = NS). RFA and laser literature demonstrate a wide spectrum of loss rates (up to 45%) and neurologic complication rates (10%–30%), which possibly vary with specific pathophysiology, fetal number, and gestational age. To date, there is no accepted delineation of outcomes by specific diagnosis or gestational age, and given the several continuous and dichotomous variables analyzed, there are not enough published cases to determine a general explanation of variance for risks and outcomes. Rao and colleagues’ experience replicates a small number of cases from other reports. However, it does seem physiologically reasonable that MC twins with vascular pathophysiology could be more prone to poor outcomes from procedural disruption of such circulation. Cases with no, minimal, or structural abnormalities would likely have more intrinsic reserves to tolerate stress from RFA or other procedures.