ORIGINAL ARTICLE Outcomes of stage I TTTS or liquor discordant twins: a single-centre review Ellen Hinch 1 , Amanda Henry 1,2 , Isabella Wilson 1 and Alec W. Welsh 1,2 * 1 School of Women’s and Children’s Health, University of New South Wales, Sydney, New South Wales, Australia 2 Department of Maternal Fetal Medicine, Royal Hospital for Women, Sydney, New South Wales, Australia *Correspondence to: A. W. Welsh. E-mail: alec.welsh@unsw.edu.au ABSTRACT Objectives To investigate rates of progression, regression and stabilisation and outcomes for stage I twin–twin transfusion syndrome (TTTS) and significant liquor discordant (LD) monochorionic diamniotic (MCDA) twins referred to the New South Wales Fetal Therapy Centre between June 2007 and May 2013. Methods Retrospective cohort study of 329 monochorionic referrals, of whom 47 had LD and 28 had stage I TTTS at presentation; 43 were stage I or higher at any time during surveillance. Clinical progression, rates of therapy, survival and associated complications were evaluated. Results Of stage I cases, 64% (18/28) remained stable or regressed, with 60% (6/10) of those progressing becoming at least stage II within 2 weeks. Of LD cases, 7/47 (15%) progressed to stage I TTTS, 8/47 (17%) to stage II or higher and 3/ 47 (6%) to selective intrauterine growth restriction (38% total). Conclusion While a stable clinical picture was the most common outcome in stage I/LD presentations, progression to stage ≥ II TTTS occurred in 36 and 17% respectively, indicating that LD is not a benign finding. Rapid progression in the majority of progressive cases and modest overall survival rates support close surveillance of these pregnancies and investigation of laser therapy as a first-line treatment of stage I TTTS. © 2016 John Wiley & Sons, Ltd. Funding sources: None Conflicts of interest: None declared INTRODUCTION Twin–twin transfusion syndrome (TTTS) complicates approximately 15% of monochorionic diamniotic (MCDA) twin pregnancies, 1 with an untreated mortality rate of up to 80%. 2,3 The shared placental vasculature in MCDA pregnancies is largely responsible for their excess mortality compared with dichorionic diamniotic (DCDA) pregnancies, with fetal loss in MCDA twins attributable both to TTTS and to a lesser extent to selective intrauterine growth restriction (sIUGR). 3,4 Simple liquor discordance often precedes the development of sIUGR and TTTS and is associated with adverse outcomes, 5 but perinatal mortality is reported to be lower than when diagnostic criteria for TTTS are met. 6 The pathophysiology of TTTS has been documented extensively. 1,7–11 Alterations in circulating volume for the donor and recipient resulting from the transfusion results in the characteristic signs of oligohydramnios in the donor gestational sac and polyhydramnios in the recipient gestational sac. 8,10,11 The Quintero staging system 12 is used to identify stages of disease severity and guide management options. Increasing stage is generally associated with increased disease severity, reduced perinatal survival and increased long-term morbidity. 13,14 While the majority of stage I cases remain stable or regress for cases that do progress, the majority do so over a short time period and progress to at least stage III. 2,15,16 Current management for stage I or liquor discordant cases is most commonly conservative 12,17,18 with favourable outcomes. 19,20 This clinical strategy is based upon experience rather than a large body of evidence, as to date there has been limited evidence published 2,15,16 with only one article evaluating the issue of progression of stage I TTTS in detail. 2 There is a relative clinical equipoise regarding management of stage I; while there is the potential for rapid progression of the disease, this must be balanced against the potential for procedural complications of laser therapy. This justifies a current randomised clinical comparing laser and conservative management in stage I TTTS cohorts. 21 Given the paucity of published literature, we aimed in this study to see whether our experience substantiates conservative management for stage I TTTS. The sporadic nature of screening ultrasound (generally fortnightly from 16 to 26 weeks) introduces an artificial timing to the diagnosis of early TTTS, so we examined those cases that were referred with significant liquor discordance as well, as many were labelled as Prenatal Diagnosis 2016, 36, 507–514 © 2016 John Wiley & Sons, Ltd. DOI: 10.1002/pd.4814