The role of superficial anastomoses on fetal survival after laser treatment for twin-twin transfusion syndrome: a subanalysis of the sequential trial

Abstract

Background: The role of placental superficial anastomoses in twin-twin transfusion syndrome remains unclear. Arterioarterial anastomoses may serve a protective role in preventing twin-twin transfusion syndrome. However, after progression to twin-twin transfusion syndrome and requisite laser treatment, recent studies suggest that the presence of an arterioarterial anastomoses may impart a worse prognosis.

Objective: To examine the association between placental superficial anastomoses and survival after laser surgery for twin-twin transfusion syndrome in a large cohort of patients who prospectively underwent fetoscopic mapping of placental vascular connections.

Study design: This is a post hoc analysis of data collected in the Sequential Trial, a randomized controlled trial comparing the sequential and the selective laser techniques for treating twin-twin transfusion syndrome patients between 16 and 26 gestational weeks. This trial found laser surgery in patients who had superficial anastomoses (ie, arterioarterial or venovenous anastomoses) were 67% less likely to result in donor twin perinatal survival (adjusted odds ratio, 0.33 [0.20-0.54], P<.001). In Part 1 of the present study, we developed a multiple logistic regression model for donor survival at birth based on the following 4 groups of the entire cohort: No superficial anastomoses, venovenous anastomoses only, only 1 arterioarterial anastomoses, and 2 or more arterioarterial anastomoses. In Part 2, we selected only those with arterioarterial anastomoses and modeled donor survival by the arterioarterial anastomoses count and attendant presence of any venovenous anastomoses. To construct the model, patients were categorized into 4 different groups: 2 or more arterioarterial anastomoses and no venovenous anastomoses, 2 or more arterioarterial anastomoses and 1 or more venovenous anastomoses, only 1 arterioarterial anastomoses and no venovenous anastomoses, and only 1 arterioarterial anastomoses and 1 or more venovenous anastomoses (reference).

Results: The distribution of the 642 patients who participated in the randomized controlled trial was no superficial anastomoses (n=466, 72.6%), venovenous anastomoses only (n=24, 3.7%), only 1 arterioarterial anastomoses (n=134, 20.9%), and 2 or more arterioarterial anastomoses (n=18, 2.8%). Donor twin perinatal survival was as follows: no superficial anastomoses (90.3%), venovenous anastomoses only (75.0%), only 1 arterioarterial anastomoses (73.1%), and 2 or more arterioarterial anastomoses (44.4%) (P<.0001). Recipient survival did not differ across the 4 groups. In Part 1, after controlling for donor twin fetal growth restriction, surgery in those with 2 or more arterioarterial anastomoses or only 1 arterioarterial anastomoses was less likely to result in donor survival (adjusted odds ratio, 0.07 [0.02-0.21], P<.0001 and adjusted odds ratio, 0.32 [0.18-0.54], P<.0001, respectively), compared with those with no superficial anastomoses. In Part 2, among those with arterioarterial anastomoses, donor survival varied with arterioarterial anastomoses count (only 1 arterioarterial anastomoses 98 [73.1%] vs 2 or more arterioarterial anastomoses 8 [44.4%], P=.026). The adjusted odds ratio for donor twin survival also varied by the presence of 1 or more venovenous anastomoses (reference only 1 arterioarterial anastomoses and 1 or more venovenous anastomoses): 2 or more arterioarterial anastomoses and no venovenous anastomoses (adjusted odds ratio, 0.02 [0.00-0.24], P=.002), 2 or more arterioarterial anastomoses and 1 or more venovenous anastomoses (adjusted odds ratio 0.24 [0.04-1.51], P=.128), and only 1 arterioarterial anastomoses and no venovenous anastomoses (adjusted odds ratio, 0.32 [0.09-1.10], P=.071). Donor twin fetal growth restriction was noncontributory.

Conclusion: The type and number of superficial anastomoses were associated with donor (but not recipient) twin survival after laser surgery for twin-twin transfusion syndrome, irrespective of the presence of donor twin fetal growth restriction. Overall, poor donor twin survival was associated with the presence of arterioarterial anastomoses, and among those with arterioarterial anastomoses, donor survival was especially poor in cases with >1 arterioarterial anastomoses and no corresponding venovenous anastomoses.

Keywords: TTTS; arterio-arterial anastomosis; critical abnormal Dopplers; donor twin; fetal demise; fetal surgery; feto-fetal transfusion syndrome; fetoscopic surgery; laser ablation; laser photocoagulation of communicating vessels; monochorionic twins; multifetal gestation; recipient twin; sequential trial; vascular communications; veno-venous anastomosis.