190: Optimal surveillance of monochorionic-diamniotic twins for twin-twin transfusion syndrome

Abstract

Biweekly surveillance ultrasound (US) examination is a strategy recommended to detect early twin-twin transfusion syndrome (TTTS) in monochorionic-diamniotic (MCDA) twins. However, data to support this frequency of surveillance are scarce. Our objective was to determine whether a biweekly scanning paradigm can reliably detect TTTS at an early stage (i.e. < Quintero stage II). This is a retrospective cohort study of women with MCDA twin pregnancies whose first US exam occurred at our center between 2012 and 2018. Women with uncertain chorionicity, less than 2 serial US exams, or those followed outside of our healthcare system were excluded. Routine surveillance consisted of an US exam every 2 weeks starting at 16 weeks gestational age (GA). Univariate analysis of US exam patterns and pregnancy characteristics was performed comparing women that had TTTS to those who did not. For women diagnosed after at least one normal US examination, GA and Quintero stage at diagnosis and length of time since the last normal US exam was determined to assess whether the frequency of US examination was adequate. To assess whether the initial screening US was early enough to detect evolving TTTS, women diagnosed with TTTS on their first US were considered separately. Of 409 women with MCDA twins that met inclusion criteria, 46 (11.3%) developed TTTS. Women with TTTS had less time between scans (7.4 ± 7.6 vs. 12.7 ± 8.0 days, p < 0.01), but baseline characteristics were otherwise similar between the groups (Table 1). Among women with TTTS, 25 (54.4%) were diagnosed at their first US while 21 (46.6%) were diagnosed at a later US. Those diagnosed at the first US had similar GA (20.3 ± 3.8 vs. 22.3 ± 4.9, p = 0.16) and Quintero stage (median II vs. III, p = 0.34) as those diagnosed at a later US exam. The majority of TTTS detected after at a later US (i.e. >1 US) was diagnosed within 2 weeks of the last normal US (16/21, 76%). Most of these twins (9/16, 56%, p = 0.09) had stage II or greater disease on diagnosis (Figure 1). In this cohort of women that had biweekly ultrasounds, most cases of TTTS were detected at an advanced stage (Quintero stage > I). This suggests that biweekly US alone is not adequate to diagnose early TTTS. Further research is required to determine whether more frequent US screening may improve early detection. For women diagnosed on first US, it is unclear from this analysis whether earlier US would detect TTTS earlier.View Large Image Figure ViewerDownload Hi-res image Download (PPT)