Velamentous cord insertion in monochorionic twins with or without twinetwin transfusion syndrome: Does it matter? T. Costa-Castro a, * , S. De Villiers b , N. Montenegro a , M. Severo c , D. Oepkes d , A. Matias a , E. Lopriore b a Department of Obstetrics and Gynecology, São João Hospital Center, Medical Faculty University of Porto, Porto 4200 e 319, Portugal b Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, Leiden, The Netherlands c Epidemiology Unit, Medical Faculty University of Porto, Porto, Portugal d Division of Fetal Medicine, Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands article info Article history: Accepted 13 August 2013 Keywords: Monochorionic twins Twinetwin transfusion syndrome Velamentous cord insertion Severe birth weight discordance Intrauterine fetal demise abstract Objective: To study the association between velamentous cord insertion (VCI) and different outcomes in monochorionic twins with and without twinetwin transfusion syndrome (TTTS). Methods: We recorded the cord insertion type in all consecutive monochorionic placentas examined in two tertiary medical centers. The association between VCI and several outcomes was estimated. Results: A total of 630 monochorionic placentas with TTTS (n ¼ 304) and without TTTS (n ¼ 326) were studied. The incidence of VCI in the TTTS and non-TTTS group was 36.8% and 35.9%, respectively (P ¼ 0.886). The presence of VCI in one twin was significantly associated with small for gestational age (SGA) status (odds ratio [OR] 1.45, 95% CI 1.13,1.87) and severe birth weight discordance (OR 3.09, 95% CI 1.93, 4.96). Our results also showed significant interaction between TTTS and VCI when we considered intrauterine fetal demise (IUFD) and gestational age (GA) at birth. The prevalence of IUFD in mono- chorionic pregnancies without TTTS increased from 4.6% to 14.1% in the presence of VCI (P ¼ 0.027). In the TTTS group, the prevalence of IUFD was comparable in the absence or presence of VCI. Similarly, GA at birth was significantly lower in the presence of VCI only in the non-TTTS group. Conclusion: Our findings suggest that VCI is not associated with the development of TTTS but increases the risk of adverse outcomes. Both VCI and TTTS independently increase the prevalence of IUFD and lower GA at birth in a similar way, showing that VCI is an important indicator of adverse perinatal outcome in monochorionic twins. Ó 2013 Published by Elsevier Ltd. 1. Introduction Twinetwin transfusion syndrome (TTTS) is a complication of monochorionic twin pregnancies and results from unbalanced inter-twin blood transfusion via placental vascular anastomoses. Although vascular anastomoses are invariably found in almost all monochorionic placentas, only 10% will eventually develop TTTS [1,2]. Differences in angio-architecture, among those the absence of arterio-arterial anastomoses, are one of the major factors involved in the development of TTTS [1e4]. However, angio-architecture alone does not fully explain the pathophysiology of TTTS [1e4]. Several other hypotheses on the pathogenesis of TTTS have been proposed, including utero-placental insufficiency and paradoxic activation of fetal vasoactive and humoral factors [3,4]. In addition, several authors found higher incidence of vela- mentous cord insertions (VCI) in TTTS placentas and hypothesized that VCI may lead to utero-placental insufficiency, subsequently establishing a vicious cycle resulting in the development of TTTS [5e8]. However, these hypotheses were mostly unsubstantiated or based on small studies [5e8]. In contrast, other recent reports show that the incidence of velamentous or marginal cord insertion is similar in monochorionic twins with and without TTTS [9e11]. Intrigued by these conflicting results, we set up a large study to shed more light on the relation between VCI and TTTS. The objec- tive of this study was to estimate the incidence of VCI in a large group of monochorionic twins with and without TTTS and study outcomes associated with VCI. 2. Material and methods All consecutive placentas of monochorionic twin pregnancies examined at the University Medical Center of Porto (Portugal) and Leiden (The Netherlands) between June 2002 and September 2012 were included in this study. Monochorionicity was * Corresponding author. Tel.: þ351 225512100; fax: þ351 225025766. E-mail address: teresacostacastro@gmail.com (T. Costa-Castro). Contents lists available at ScienceDirect Placenta journal homepage: www.elsevier.com/locate/placenta 0143-4004/$ e see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.placenta.2013.08.009 Placenta xxx (2013) 1e6 Please cite this article in press as: Costa-Castro T, et al., Velamentous cord insertion in monochorionic twins with or without twinetwin transfusion syndrome: Does it matter?, Placenta (2013), http://dx.doi.org/10.1016/j.placenta.2013.08.009