Inter-twin contact in a case of monochorionic diamniotic twins with acrania of one twin fetus at 10–13 weeks’ gestation

To the Editor, Anencephaly can be reliably diagnosed using ultrasound late in the first trimester of pregnancy [1]. The prevalence of anencephaly in twins is higher than that in singleton pregnancies, and the prevalence of discordance in anencephaly in monochorionic twins is higher than that in dichorionic twins [2]. There have been only two reports on conventional twodimensional (2D) sonographic assessment of fetal behavior in twins discordant because of anencephaly after 20 weeks of gestation [3, 4]. However, there has been no report on four-dimensional (4D) sonographic assessment of intertwin contact in twins discordant because of anencephaly in utero. To the best of our knowledge, this is the first report on 4D sonographic assessment of inter-twin contact in a case of monochorionic diamniotic (MD) twins with acrania of one twin fetus late in the first trimester. A 28-year-old Japanese woman, gravida 3, para 1, visited our hospital because of secondary amenorrhea, and MD twin pregnancy at 7 weeks and 4 days was diagnosed. At 11 weeks and 4 days, twin pregnancy with acrania of one twin fetus was diagnosed (Fig. 1). The parents were informed about the lethality of the affected twin fetus, but they elected to continue the pregnancy. At 25 weeks and 1 day, she was admitted to our hospital because of threatened premature labor (short cervix and irritable uterine contractions). At 38 weeks and 4 days, the first of two female infants (anencephalic twin), weighing 1,948 g, and the other infant (second twin), weighing 2,372 g (Apgar score 7 at 1 min and 9 at 5 min; umbilical artery blood pH 7.089), were delivered by elective cesarean section because of two previous cesarean sections. The anencephalic twin died soon after delivery. Permission to conduct an autopsy was not granted by the parents. The second twin is doing well. Detailed descriptions of the data-collecting methods and measurement procedures used in this patient have been presented in a previous publication [5]. In brief, examinations were performed for 30 min with transabdominal 4D sonography at 11 weeks and 4 days and 13 weeks and 1 day of pregnancy, respectively. She was asked whether she would agree to a 30-min observation of fetal movements and inter-twin contact after undergoing routine sonographic examinations. This study was approved by the local ethics committee of Kagawa University School of Medicine, and standardized written informed consent was obtained from the patient. All 4D examinations were performed using Voluson 730 Expert (GE Medical Systems, Milwaukee, WI) with a transabdominal 2–5-MHz transducer. Ten types of inter-twin contact (head to head, head to arm, head to trunk, head to leg, arm to arm, arm to trunk, arm to leg, trunk to trunk, trunk to leg, and leg to leg) were analyzed during playback of the video recordings. The total number of all inter-twin contacts was determined by a single experienced observer (M.S.) and compared to the quartile range obtained from normal MD twins [5]. The frequencies of ten types of inter-twin contact were also compared to the quartile ranges obtained from normal MD twins [6]. The total number of inter-twin contacts in this patient was low compared to those of normal MD twin fetuses at 10–11 and 12–13 weeks’ gestation (Fig. 2). The frequencies of 10 types of inter-twin contact at 10–11 weeks were almost within quartile ranges (Fig. 3), T. Hata (&) K. Kanenishi U. Hanaoka M. Sasaki T. Yanagihara Department of Perinatology and Gynecology, Kagawa University School of Medicine, 1750-1 Ikenobe, Miki, Kagawa 761-0793, Japan e-mail: toshi28@med.kagawa-u.ac.jp