Hindawi Publishing Corporation Case Reports in Obstetrics and Gynecology Volume 2012, Article ID 783408, 3 pages doi:10.1155/2012/783408 Case Report Spontaneous Resolution of Mirror Syndrome following Demise of Hydropic Twin Kate E. Oliver, Kimberly W. Hickey, and Scott M. Petersen Prenatal Assessment Center, Department of Obstetrics and Gynecology, Walter Reed National Military Medical Center, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA Correspondence should be addressed to Scott M. Petersen, scott.petersen@med.navy.mil Received 13 August 2012; Accepted 24 September 2012 Academic Editors: A. Awonuga, A. Fujimoto, and O. Picone Copyright © 2012 Kate E. Oliver et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Maternal mirror syndrome is a rare consequence of fetal hydrops. By convention, delivery is recommended in pregnancies complicated by mirror syndrome due to grave fetal prognosis. We describe a case of a dichorionic, diamniotic twin gestation complicated by hydrops fetalis of twin B. The patient declined selective feticide. Two weeks later, intrauterine fetal demise of fetus B was diagnosed and complete resolution of mirror syndrome followed. Unaddressed, mirror syndrome can lead to signiﬁcant maternal and fetal complications. This case illustrates resolution of mirror syndrome following spontaneous intrauterine demise of the hydropic fetus. 1. Introduction Mirror syndrome is a rare consequence of severe fetal hydrops of both immune and nonimmune etiologies, with fewer than 100 cases previously described in the literature [1]. JW Ballantyne reported the ﬁrst case in 1892, and subsequently, cases have been published using a variety of terms, including Ballantyne’s syndrome, maternal hydrops syndrome, pseudotoxemia, and triple edema syndrome, among others [2–7]. The etiology of mirror syndrome remains unclear, although an underlying severe fetal hydrops is proximate to the development of the condition [2, 5]. Mirror syndrome traditionally was diagnosed in cases where fetal hydrops evolved in the setting of an underlying fetal anemia, typically secondary to rhesus isoimmunization [2, 4–6]. More recently, cases of mirror syndrome have been reported as a result of fetal hydrops stemming from nonimmune etiologies, such as fetal structural anomalies [6], cardiac abnormalities [2], fetal arrhythmias [4], and intrauterine infection [3]. The development of mirror syndrome portends poor prognosis and impending fetal death [2, 3, 6]. Uncom- monly, mirror syndrome has resolved with treatment and improvement of the hydrops of the aﬀected fetus, although some causes are inherently uncorrectable [3, 5, 6]. In one recent account, maternal mirror syndrome arising from a parvovirus B19 infection resolved with spontaneous res- olution of the associated fetal hydrops [3]. Another case report demonstrated resolution of mirror syndrome with selective reduction of the aﬀected twin [8], while a third case of mirror syndrome resolved with correction of the fetal tachyarrhythmia [4]. To our knowledge, there are no reported cases of resolution of mirror syndrome with spontaneous demise of the aﬀected fetus. Should maternal mirror syndrome fail to resolve either spontaneously, with selective fetal reduction, or following treatment aimed at correcting the underlying fetal etiology of the hydrops, delivery is usually obligatory for maternal indications [6, 8]. 2. Case We present a case of a 38-year-old gravida 4 para 1021 with dichorionic-diamniotic IVF/ICSI twin gestation. The patient’s past medical and surgical histories were unremark- able. Her obstetrical history was notable for a prior IVF gestation which resulted in a spontaneous vaginal delivery at term. At her initial prenatal visit at 9-week estimated gestational age, the patient’s blood pressure was noted to be 122/65 mmHg, and her most recent prepregnancy weight