CROSSMARK_logo_3_Test 1 / 1 ORIGINAL ARTICLE Obstetrics & Gynecology https://crossmarhttps://doi.org/10.3346/jkms.2017.32.12.2016k-cdn.crossref.org/widget/v2.0/logos/CROSSMARK_Color_square.svg 2017-03-16 • J Korean Med Sci 2017; 32: 2016-2020 Prediction of Amnionicity Using the Number of Yolk Sacs in Monochorionic Multifetal Pregnancy Sue Yeon Park,1 Jin Hoon Chung,2 The purpose of this article was to evaluate the accuracy of predicting amnionicity using the You Jung Han,2 Si Won Lee,2 number of yolk sacs by diagnostic ultrasound examination in monochorionic (MC) and Moon Young Kim2 multifetal pregnancies between 7 + 0 and 9 + 6 gestational weeks. A total of 97 patients with MC multifetal pregnancies underwent early ultrasound examination from 2004 to 1Department of Obstetrics and Gynecology, Lin Women’s Hospital, Seoul, Korea; 2Department of 2014 at Cheil General Hospital and Women’s Healthcare Center. All patients for whom the Obstetrics and Gynecology, Cheil General Hospital number of yolk sacs was reported were included in this study. We compared the number of and Women’s Healthcare Center, Dankook University yolk sacs with amnionicity confirmed by an intertwine membrane. Overall, there was a College of Medicine, Seoul, Korea 9.3% (9 cases) discrepancy in number of yolk sacs and amnionicity (4.3% for Received: 22 January 2017 monochorionic diamniotic, 36.4% for monochorionic monoamniotic, and 33% for Accepted: 9 September 2017 monochorionic triamniotic). Among the 9 cases with discrepancies, 4 cases with 2 yolk sacs were confirmed as monoamniotic pregnancies and 4 MC twin pregnancies showing a Address for Correspondence: single yolk sac were diagnosed as diamniotic twin pregnancies. One case with 2 yolk sacs Jin Hoon Chung, MD, PhD Department of Obstetrics and Gynecology, Cheil General was identified as a triamniotic triplet pregnancy. In 9.3% of MC gestations, the number of Hospital and Women’s Healthcare Center, Dankook University yolk sacs was not correlated with the number of amnions in our study. To determine College of Medicine, 17 Seoae-ro 1-gil, Jung-gu, Seoul 04619, Korea amnionicity in MC multifetal pregnancies, we recommend careful evaluation not of the E-mail: [email protected] number of yolk sacs but the presence or absence of intertwine dividing membrane after 8 gestational weeks. Keywords: Amnionicity; Multifetal Pregnancy; Twins; Ultrasound; Monochorionic Twin; Yolk Sac INTRODUCTION the dividing amniotic membrane (5). The amniotic membrane develops concurrently with the yolk sac, but it is difficult to vi- The incidence of multifetal pregnancy has increased with the sualize early in the first trimester because the membrane is close- use of assisted reproductive technologies. Multifetal pregnan- ly applied to the developing embryo without amniotic fluid be- cies increase the rate of preterm births, which compromise neo- tween the embryo and the amnion. The amnion only becomes natal survival and increase the risk of lifelong disability. The in- visible once there is enough fluid separating the embryo from fant mortality rate for multiple births is five times the rate as that the membrane. Therefore, the number of yolk sacs may be used for a singleton (1). These risks are magnified further with triplet to diagnose amnionicity initially (6). or quadruplet births. Recently, the accuracy of the relationship between the num- The determination of chorionicity antenatally in twin preg- ber of yolk sacs and amnionicity has been called into question nancy is important for predicting pregnancy complications (2). (7-9). In addition, we have experienced several cases of MC mul- It is well known that monochorionic (MC) twin pregnancies are tifetal gestations with discrepancies between the number of yolk associated with higher mortality and morbidity than dichorion- sacs and amnionicity. To the best of our knowledge, previous ic twin pregnancies due to hemodynamic imbalance (3). Mono- reports have been case reports or very small studies. Therefore, amniotic (MA) twin pregnancies account for only 1% of all mono- we evaluated the accuracy of the number of yolk sacs for pre- zygotic twins and are associated with high fetal death rates from dicting amnionicity in MC multifetal pregnancies during early cord entanglement, congenital anomalies, and preterm birth first trimester ultrasound examination. (4). Therefore, accurate determination of amnionicity is an im- portant first step for establishing a clinical management plan MATERIALS AND METHODS and counseling women with MC multifetal pregnancies and their family members about pregnancy outcomes. This was a retrospective analysis of prospectively collected data Determination of amnionicity in MC multifetal pregnancies from patients with MC multifetal gestations from October 2004 is typically done around 8 weeks of gestation by visualization of to December 2014 at Cheil General Hospital and Women’s Health- © 2017 The Korean Academy of Medical Sciences. pISSN 1011-8934 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. eISSN 1598-6357 Park SY, et al. • Prediction of Amnionicity in Monochorionic Multifetal Pregnancy care Center. During the study period, a total of 97 viable MC mul- Review Board of Cheil General Hospital (Seoul) (IRB No. CGH- tifetal pregnancies were identified via ultrasound between 7 + 0 IRB-2015-54). The need to obtain informed consent was waived. and 9 + 6 weeks of gestation. Ultrasonography was performed using transvaginal and transabdominal transducers with one of RESULTS the following ultrasound models (Voluson E8, Voluson 730; GE Healthcare, Milwaukee, WI, USA) by five obstetricians, each with During the study period, a total of 97 cases of MC multifetal preg- more than five years of experience performing first trimester nancy were identified, including 83 cases of diamniotic (DA) scans. In our center, all pregnant women with multifetal preg- twins, 11 cases of MA twins, and 3 cases of TA triplets. The mean nancies were advised to receive fetal ultrasonography between maternal age of the study group was 32.2 ± 3.9 years old and 71 7 + 0 and 9 + 6 gestational weeks for determination of chorion- (66.0%) of the women were nulliparous. The median GA at the icity and amnionicity. When determination of chorionicity or first ultrasound scan was 8.0 ± 1.3 weeks of gestation. The most amnionicity was uncertain, the patient underwent sonography common method of conception was natural (69%), and other again by another senior staff. Follow-up fetal sonography was maternal characteristics are shown in Table 1. performed, usually two weeks later at 9–11 weeks of gestation Nine cases (9.3%) showed discrepancies between the num- by two examiners. In each scan, the number of gestational sacs, ber of yolk sacs determined on initial ultrasound examination number of yolk sacs within each gestational sac, presence or and the amnionicity confirmed by the presence and number of absence of a dividing membrane, number of fetuses, crown-rump dividing membranes in serial follow-up sonography and/or length (CRL), fetal heart rate, and presence or absence of asso- gross postpartum evaluation of the membrane (Table 2). In the ciated fetal anomaly were documented. Chorionicity and amnionicity were documented by serial ul- Table 2. Discrepancy rates between confirmed amnionicity and the number of yolk trasound assessment of the dividing membrane and/or confirm- sacs on ultrasonography ed by postpartum pathologic examination of the placenta. Cho- Confirmed No. of Yolk sacs Discrepancy rionicity was determined by assessing the number of gestation- amnionicity cases No. Cases rate al sacs and a dividing membrane within the gestational sac was MCMA 11 (11.3) 1 7 4/11 (36.3) considered adequate evidence of diamnionicity. When two di- 2 4 viding membranes were identified within a single gestational MCDA 83 (85.6) 1 4 4/83 (4.8) 2 79 sac, we determined the case to be a MC triamniotic (TA) triplet MCTA 3 (3.1) 1 0 1/3 (33.3) pregnancy. We reviewed the all images in each case for the pur- 2 1 pose of the study. 3 2 Gestational age (GA) was calculated from the first day of the Total 97 - - 9/97 (9.3) last menstrual period and was confirmed by CRL measurement Data are shown as number (%). in the first trimester of pregnancy. When estimated GA by men- MCMA = monochorionic monoamniotic, MCDA = monochorionic diamniotic, MCTA = monochorionic triamniotic. strual date varied from ultrasound date by more than 5 days, we used the ultrasound performed between 7 + 0 and 9 + 6 weeks of pregnancy to estimate GA. In cases of in vitro fertilization (IVF), the ovum pick-up day was defined as intrauterine pregnancy (IUP) 2 + 0 gestational weeks. Ethics statement Ethical approval of this study was provided by the Institutional Table 1. Clinical characteristics of the study population Characteristic Value Maternal age, yr 32.2 ± 3.9 Nulliparity 71 (66.0) GA at initial US scan, wk 8.0 ± 1.3 Method of conception Natural 67 (69.1) IVF 26 (26.8) Ovulation-induction 4 (4.1) Fig. 1. Transvaginal ultrasound at 9 weeks of gestation demonstrates two yolk sacs Data are shown as mean ± standard deviation or number (%). in a MCMA pregnancy. GA = gestational age, US = ultrasonography, IVF = in vitro fertilization. MCMA = monochorionic monoamniotic. https://doi.org/10.3346/jkms.2017.32.12.2016