Ultrasound Obstet Gynecol 2014; 44: 722–724 Published online 11 November 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/uog.13403
Partial monochorionic and monoamniotic twin pregnancies: a report of two cases S. GALJAARD*†, P. MOERMAN‡§, A. CORVELEYN¶**, R. DEVLIEGER*† and L. LEWI*† *Department of Development and Regeneration, Katholieke Universiteit Leuven, Leuven, Belgium; †Department of Obstetrics and Gynecology, University Hospitals Leuven, Leuven, Belgium; ‡Department of Imaging and Pathology, Katholieke Universiteit Leuven, Leuven, Belgium; §Department of Pathology, University Hospitals Leuven, Leuven, Belgium; ¶Department of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; **Centrum voor Menselijke Erfelijkheid, University Hospitals Leuven, Leuven, Belgium
K E Y W O R D S: diamniotic twin pregnancy; monochorionic; partial monoamniotic; placenta; prenatal ultrasound
ABSTRACT Monochorionic (MC) twin pregnancies are at increased risk of adverse outcome because of the vascular anastomoses that connect the two fetal circulations. MC monoamniotic (MA) twins are at an even higher risk because of their almost universal cord entanglement and possible compression, which can cause an acute transfusion imbalance between the twins. Chorionicity and amnionicity should be determined during the first-trimester ultrasound examination to identify high-risk MC and MA twin pregnancies for which a fortnightly follow-up may improve outcome. Although this can be achieved readily by assessing and counting the membranes that separate the twins, some pitfalls may occur. We present our observations of two monozygotic twin pairs with an intermediate type of monodichorionic and monodiamniotic twin pregnancy. The first was recognized during the first-trimester scan and the second during the second-trimester scan. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
CASE REPORTS The first case was a spontaneous twin pregnancy of a 25-year-old woman, gravida 2 para 1, referred at 12 weeks’ gestation for chorionicity determination. Ultrasound showed only two thin separating amniotic membranes at the lower part of the intertwin septum and one thick chorionic membrane in conjunction with two thin amniotic membranes at the upper part (Figure 1), resulting in the diagnosis of a partial monochorionic (MC) twin pregnancy. The pregnancy was followed up as an MC twin pregnancy with fortnightly ultrasound examinations. The pregnancy was uneventful and the patient delivered
two healthy girls of 2535g and 2595g at 36 weeks’ gestation. Postnatal macroscopic evaluation of the intertwin membrane confirmed our diagnosis, showing both an opaque and a translucent part of the septum (Figure 2). Placental injection documented the presence of vascular anastomoses across the MC part of the septum. Pathological examination of the intertwin septum confirmed both the amnion–amnion and amnion–chorion–amnion attachment, indicating a partial MC and dichorionic (DC) septum (Figure 3), as was diagnosed at the first-trimester scan. DNA fingerprinting using fibroblasts cultured from the umbilical cords confirmed monozygosity. The second case was a twin pregnancy conceived by intracytoplasmatic sperm injection in a 26-year-old woman, gravida 3 para 1. The first-trimester scan showed two thin amniotic membranes (Figure 4, inset), typical in an MC diamniotic (DA) twin pregnancy, and a fortnightly follow-up scan was recommended. Re-evaluation at 20 weeks’ gestation showed that the intertwin septum no longer separated the two twins, but that both were on the same side of the septum and their cords were entangled. The initial diagnosis of a diamniotic pregnancy was therefore changed to a partial monoamniotic (MA) pregnancy. From 28 weeks onwards, the woman was managed as an inpatient to provide fetal surveillance and treatment for fetal lung maturation, as is usual for MA pairs1 . An emergency Cesarean section was performed at 31 weeks’ gestation because of preterm prelabor rupture of membranes and the clinical suspicion of placental abruption. Two healthy boys of 1630g and 1440g were delivered. Postpartum macroscopic evaluation confirmed the presence of cord entanglement and revealed a partial DA intertwin septum between the cord insertions (Figure 4). Examination of the injected placenta documented the presence of vascular anastomoses, as typically seen in MC placentas.
Correspondence to: Dr L. Lewi, Department of Obstetrics and Gynecology, University Hospitals Leuven, Herestraat 49, B-3000 Leuven, Belgium (e-mail: [email protected]) Accepted: 28 April 2014
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
CASE REPORT
Partial MC and MA twins
723
Figure 1 First-trimester ultrasound images from a partial monochorionic twin pregnancy showing a thick chorionic membrane with two thin amniotic membranes at the upper part of the intertwin septum (a) and two thin separating amniotic membranes at the lower part (b).
Figure 3 Histological view of a transverse plane of the dividing membrane in a partial monochorionic (MC) twin pregnancy. (a) Overview of both the triple layer (dichorionic) and the double layer (MC). (b) Intervening chorion visible between two amniotic layers. (c) Two single amniotic layers, representing the MC part of the septum.
Figure 2 Placental injection in a partial monochorionic (MC) twin pregnancy, documenting the presence of vascular anastomoses across the monochorionic (MC) part of the septum (arterioarterial (open arrows) and arteriovenous (filled arrows) anastomoses). Inset, postnatal macroscopic evaluation of the intertwin membrane revealing both an opaque (dichorionic) and a translucent (MC) part of the septum.
DISCUSSION In the management of twin pregnancies, the first-trimester ultrasound examination is of critical importance as it distinguishes the high-risk MC pregnancy from the lower-risk DC pregnancy with high accuracy2,3 . MC twins are considered to be at increased risk of adverse outcome compared to DC twins because of vascular anastomoses on the placenta4–6 . Also, in MC pairs, ultrasound examination allows identification of the rare MA twins who are at an even higher risk because of cord entanglement7 .
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
We report on two intermediate forms of chorionicity and amnionicity that may arise because of zygotic cleavage within the time interval just between di- and monochorionic and di- and monoamniotic twinning. The general assumption with respect to chorion separation is that the third day after fertilization is important. Separation of a fertilized ovum before then is thought to give rise to a DC twin. If cleavage occurs after 9 days of fertilization, the amniotic sac will be shared by both twins, leading to an MA twin. The incidence of partial MC and partial MA twinning is not known, but is probably rare. Factors increasing the incidence or timing of cleavage are not well known, although artificial reproductive techniques, maternal age and ethnicity have been suggested8,9 . This is the first case report of a partial MC twin diagnosed in the first trimester. The only other two reports are of a diagnosis made during fetoscopic laser treatment of twin–twin transfusion syndrome in a presumed DC twin pair10,11 . It seems important to assess the entire
Ultrasound Obstet Gynecol 2014; 44: 722–724.
Galjaard et al.
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Figure 4 (a) Postpartal macroscopic evaluation in a partial monoamniotic twin pregnancy, confirming the presence of cord entanglement and revealing a partial intertwin septum. (b) First-trimester ultrasound scan, typical of a monochorionic diamniotic pregnancy, showing two thin amniotic membranes.
intertwin septum to detect these rare partial MC pairs. In contrast to the partial MC twin, partial MA twins have been reported previously and are usually wrongly referred to as pseudo-MA twins and thought to arise from a secondary rupture12,13 . However, in our opinion, the septum may well be incomplete from the start. An incomplete septum may be difficult to recognize on a first-trimester scan. In order to recognize these rare partial MA twins, it seems important to confirm the presence of the intertwin membrane between the two fetuses at each ultrasound examination. If the intertwin septum can be seen but both twins are on the same side of the septum, this suggests a partial MA twin. In conclusion, we describe two intermediate forms of twinning, i.e. partial MC and partial MA twins. Although these cases are probably rare, the clinical implications of our findings are that the entire intertwin septum should be assessed during the first-trimester scan to rule out a partial MC twin. This will affect clinical management of the pregnancy and the timing of delivery14 . Later in pregnancy, to exclude a partial MA twin pregnancy, it seems important to verify that the intertwin septum still separates the twins. Once a partial MC or MA twin is diagnosed, it therefore seems prudent to manage these cases as true MC and MA pairs.
REFERENCES 1. Lewi L. Cord entanglement in monoamniotic twins: does it really matter? Ultrasound Obstet Gynecol 2010; 35: 139–141. 2. Caroll SG, Soothill PW, Abdel-Fattah SA, Porter H, Montague I, Kyle PM. Prediction of chorionicity in twin pregnancies at 10-14 weeks of gestation. BJOG 2002; 109: 182–186. 3. Stenhouse E, Hardwick C, Maharaj S, Webb J, Kelly T, Mackenzie FM. Chorionicity determination in twin pregnancies: how accurate are we? Ultrasound Obstet Gynecol 2002; 19: 350–352. 4. Lewi L, Cannie M, Blickstein I, Jani J, Huber A, Hecher K, Dymarkowski S, Gratacos E, Lewi P, Deprest J. Placental sharing, birthweight discordance, and vavscular anastomoses in
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
5.
6.
7.
8.
9.
10. 11.
12.
13.
14.
monochorionic diamniotic twin placentas. Am J Obstet Gynecol 2007; 197: 578.e1–8. Lewi L, Jani J, Blickstein I, Huber A, Gucciardo L, Van Mieghem T, Don´e E, Boes AS, Hecher K, Gratacos E, Lewi P, Deprest J. The outcome of monochorionic diamniotic twin gestations in the era of invasive fetal therapy: a prospective cohort study. Am J Obstet Gynecol 2008; 199: 514.e1–8. Slaghekke F, Kist WJ, Oepkes D, Pasman SA, Middeldorp JM, Klumper FJ, Walther FJ, Vandenbussche FP, Lopriore E. Twin anemia-polycythemia sequence: diagnostic criteria, classification, perinatal management and outcome. Fetal Diagn Ther 2010; 27: 181–190. Blickstein I, Aarabin B, Lewi L, Matias A, Kavak ZN, Basgul A, Kalish R, Vladareanu R, Ville Y. A template for defining the perinatal care of monochorionic twins: the Istanbul international ad hoc committee. J Perinat Med 2010; 38: 107–110. Platt MJ, Marshall A, Pharaoh PO. The effects of assisted reproduction on the trends and zygosity of multiple births in England and Wales 1974-1999. Twin Res 2001; 4: 417–421. Derom R, Orlebeke J, Eriksson A. The epidemiology of multiple births in Europe. In: Multiple Pregnancy: Epidemiology, Gestation and Perinatal Outcome. Keith LG, Papiernik E, Keith DM, Luke B (eds). Parthenon: New York, NY, 1995. 145–162. Chmait RH, Floyd R, Benirschke K. Duplicity. Am J Obstet Gynecol 2011; 205: 87.e1–2. Quintero R, Kontopoulos EV, Barness E, Steffensen TS, Hilbelink D, Chmait RH, Benirschke K, Bornick PW. Twin-twin transfusion syndrome in a dichorionic-monozygotic twin pregnancy: the end of a paradigm? Fetal Pediatr Pathol 2010; 29: 81–88. Lee KJ, Kim MK, Lee SY, Lee WS, Lee YH. Spontaneous rupture of the dividing membrane in a monochorionic pregnancy resulting in a pseudo-monoamniotic pregnancy with cord entanglement. J Obstet Gynecol Res 2012; 38: 863–866. Jeanty C, Newman E, Jeanty P, Rodts-Palenik S. Prenatal diagnosis of spontaneous septostomy in dichorionic diamniotic twins and review of the literature. J Ultrasound Med 2010; 29: 455–463. Breathnach FM, McAuliffe FM, Geary M, Daly S, Higgins JR, Dornan J, Morrison JJ, Burke G, Higgins S, Manning F, Caroll S, Malone FD; Perinatal Ireland Research Consortium. Optimum timing for planned delivery of uncomplicated monochorionic and dichorionic twin pregnancies. Obstet Gynecol. 2012; 119: 50–59.
Ultrasound Obstet Gynecol 2014; 44: 722–724.
Partial monochorionic and monoamniotic twin pregnancies: a report of two cases S. GALJAARD*†, P. MOERMAN‡§, A. CORVELEYN¶**, R. DEVLIEGER*† and L. LEWI*† *Department of Development and Regeneration, Katholieke Universiteit Leuven, Leuven, Belgium; †Department of Obstetrics and Gynecology, University Hospitals Leuven, Leuven, Belgium; ‡Department of Imaging and Pathology, Katholieke Universiteit Leuven, Leuven, Belgium; §Department of Pathology, University Hospitals Leuven, Leuven, Belgium; ¶Department of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium; **Centrum voor Menselijke Erfelijkheid, University Hospitals Leuven, Leuven, Belgium
K E Y W O R D S: diamniotic twin pregnancy; monochorionic; partial monoamniotic; placenta; prenatal ultrasound
ABSTRACT Monochorionic (MC) twin pregnancies are at increased risk of adverse outcome because of the vascular anastomoses that connect the two fetal circulations. MC monoamniotic (MA) twins are at an even higher risk because of their almost universal cord entanglement and possible compression, which can cause an acute transfusion imbalance between the twins. Chorionicity and amnionicity should be determined during the first-trimester ultrasound examination to identify high-risk MC and MA twin pregnancies for which a fortnightly follow-up may improve outcome. Although this can be achieved readily by assessing and counting the membranes that separate the twins, some pitfalls may occur. We present our observations of two monozygotic twin pairs with an intermediate type of monodichorionic and monodiamniotic twin pregnancy. The first was recognized during the first-trimester scan and the second during the second-trimester scan. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
CASE REPORTS The first case was a spontaneous twin pregnancy of a 25-year-old woman, gravida 2 para 1, referred at 12 weeks’ gestation for chorionicity determination. Ultrasound showed only two thin separating amniotic membranes at the lower part of the intertwin septum and one thick chorionic membrane in conjunction with two thin amniotic membranes at the upper part (Figure 1), resulting in the diagnosis of a partial monochorionic (MC) twin pregnancy. The pregnancy was followed up as an MC twin pregnancy with fortnightly ultrasound examinations. The pregnancy was uneventful and the patient delivered
two healthy girls of 2535g and 2595g at 36 weeks’ gestation. Postnatal macroscopic evaluation of the intertwin membrane confirmed our diagnosis, showing both an opaque and a translucent part of the septum (Figure 2). Placental injection documented the presence of vascular anastomoses across the MC part of the septum. Pathological examination of the intertwin septum confirmed both the amnion–amnion and amnion–chorion–amnion attachment, indicating a partial MC and dichorionic (DC) septum (Figure 3), as was diagnosed at the first-trimester scan. DNA fingerprinting using fibroblasts cultured from the umbilical cords confirmed monozygosity. The second case was a twin pregnancy conceived by intracytoplasmatic sperm injection in a 26-year-old woman, gravida 3 para 1. The first-trimester scan showed two thin amniotic membranes (Figure 4, inset), typical in an MC diamniotic (DA) twin pregnancy, and a fortnightly follow-up scan was recommended. Re-evaluation at 20 weeks’ gestation showed that the intertwin septum no longer separated the two twins, but that both were on the same side of the septum and their cords were entangled. The initial diagnosis of a diamniotic pregnancy was therefore changed to a partial monoamniotic (MA) pregnancy. From 28 weeks onwards, the woman was managed as an inpatient to provide fetal surveillance and treatment for fetal lung maturation, as is usual for MA pairs1 . An emergency Cesarean section was performed at 31 weeks’ gestation because of preterm prelabor rupture of membranes and the clinical suspicion of placental abruption. Two healthy boys of 1630g and 1440g were delivered. Postpartum macroscopic evaluation confirmed the presence of cord entanglement and revealed a partial DA intertwin septum between the cord insertions (Figure 4). Examination of the injected placenta documented the presence of vascular anastomoses, as typically seen in MC placentas.
Correspondence to: Dr L. Lewi, Department of Obstetrics and Gynecology, University Hospitals Leuven, Herestraat 49, B-3000 Leuven, Belgium (e-mail: [email protected]) Accepted: 28 April 2014
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
CASE REPORT
Partial MC and MA twins
723
Figure 1 First-trimester ultrasound images from a partial monochorionic twin pregnancy showing a thick chorionic membrane with two thin amniotic membranes at the upper part of the intertwin septum (a) and two thin separating amniotic membranes at the lower part (b).
Figure 3 Histological view of a transverse plane of the dividing membrane in a partial monochorionic (MC) twin pregnancy. (a) Overview of both the triple layer (dichorionic) and the double layer (MC). (b) Intervening chorion visible between two amniotic layers. (c) Two single amniotic layers, representing the MC part of the septum.
Figure 2 Placental injection in a partial monochorionic (MC) twin pregnancy, documenting the presence of vascular anastomoses across the monochorionic (MC) part of the septum (arterioarterial (open arrows) and arteriovenous (filled arrows) anastomoses). Inset, postnatal macroscopic evaluation of the intertwin membrane revealing both an opaque (dichorionic) and a translucent (MC) part of the septum.
DISCUSSION In the management of twin pregnancies, the first-trimester ultrasound examination is of critical importance as it distinguishes the high-risk MC pregnancy from the lower-risk DC pregnancy with high accuracy2,3 . MC twins are considered to be at increased risk of adverse outcome compared to DC twins because of vascular anastomoses on the placenta4–6 . Also, in MC pairs, ultrasound examination allows identification of the rare MA twins who are at an even higher risk because of cord entanglement7 .
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
We report on two intermediate forms of chorionicity and amnionicity that may arise because of zygotic cleavage within the time interval just between di- and monochorionic and di- and monoamniotic twinning. The general assumption with respect to chorion separation is that the third day after fertilization is important. Separation of a fertilized ovum before then is thought to give rise to a DC twin. If cleavage occurs after 9 days of fertilization, the amniotic sac will be shared by both twins, leading to an MA twin. The incidence of partial MC and partial MA twinning is not known, but is probably rare. Factors increasing the incidence or timing of cleavage are not well known, although artificial reproductive techniques, maternal age and ethnicity have been suggested8,9 . This is the first case report of a partial MC twin diagnosed in the first trimester. The only other two reports are of a diagnosis made during fetoscopic laser treatment of twin–twin transfusion syndrome in a presumed DC twin pair10,11 . It seems important to assess the entire
Ultrasound Obstet Gynecol 2014; 44: 722–724.
Galjaard et al.
724
Figure 4 (a) Postpartal macroscopic evaluation in a partial monoamniotic twin pregnancy, confirming the presence of cord entanglement and revealing a partial intertwin septum. (b) First-trimester ultrasound scan, typical of a monochorionic diamniotic pregnancy, showing two thin amniotic membranes.
intertwin septum to detect these rare partial MC pairs. In contrast to the partial MC twin, partial MA twins have been reported previously and are usually wrongly referred to as pseudo-MA twins and thought to arise from a secondary rupture12,13 . However, in our opinion, the septum may well be incomplete from the start. An incomplete septum may be difficult to recognize on a first-trimester scan. In order to recognize these rare partial MA twins, it seems important to confirm the presence of the intertwin membrane between the two fetuses at each ultrasound examination. If the intertwin septum can be seen but both twins are on the same side of the septum, this suggests a partial MA twin. In conclusion, we describe two intermediate forms of twinning, i.e. partial MC and partial MA twins. Although these cases are probably rare, the clinical implications of our findings are that the entire intertwin septum should be assessed during the first-trimester scan to rule out a partial MC twin. This will affect clinical management of the pregnancy and the timing of delivery14 . Later in pregnancy, to exclude a partial MA twin pregnancy, it seems important to verify that the intertwin septum still separates the twins. Once a partial MC or MA twin is diagnosed, it therefore seems prudent to manage these cases as true MC and MA pairs.
REFERENCES 1. Lewi L. Cord entanglement in monoamniotic twins: does it really matter? Ultrasound Obstet Gynecol 2010; 35: 139–141. 2. Caroll SG, Soothill PW, Abdel-Fattah SA, Porter H, Montague I, Kyle PM. Prediction of chorionicity in twin pregnancies at 10-14 weeks of gestation. BJOG 2002; 109: 182–186. 3. Stenhouse E, Hardwick C, Maharaj S, Webb J, Kelly T, Mackenzie FM. Chorionicity determination in twin pregnancies: how accurate are we? Ultrasound Obstet Gynecol 2002; 19: 350–352. 4. Lewi L, Cannie M, Blickstein I, Jani J, Huber A, Hecher K, Dymarkowski S, Gratacos E, Lewi P, Deprest J. Placental sharing, birthweight discordance, and vavscular anastomoses in
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
5.
6.
7.
8.
9.
10. 11.
12.
13.
14.
monochorionic diamniotic twin placentas. Am J Obstet Gynecol 2007; 197: 578.e1–8. Lewi L, Jani J, Blickstein I, Huber A, Gucciardo L, Van Mieghem T, Don´e E, Boes AS, Hecher K, Gratacos E, Lewi P, Deprest J. The outcome of monochorionic diamniotic twin gestations in the era of invasive fetal therapy: a prospective cohort study. Am J Obstet Gynecol 2008; 199: 514.e1–8. Slaghekke F, Kist WJ, Oepkes D, Pasman SA, Middeldorp JM, Klumper FJ, Walther FJ, Vandenbussche FP, Lopriore E. Twin anemia-polycythemia sequence: diagnostic criteria, classification, perinatal management and outcome. Fetal Diagn Ther 2010; 27: 181–190. Blickstein I, Aarabin B, Lewi L, Matias A, Kavak ZN, Basgul A, Kalish R, Vladareanu R, Ville Y. A template for defining the perinatal care of monochorionic twins: the Istanbul international ad hoc committee. J Perinat Med 2010; 38: 107–110. Platt MJ, Marshall A, Pharaoh PO. The effects of assisted reproduction on the trends and zygosity of multiple births in England and Wales 1974-1999. Twin Res 2001; 4: 417–421. Derom R, Orlebeke J, Eriksson A. The epidemiology of multiple births in Europe. In: Multiple Pregnancy: Epidemiology, Gestation and Perinatal Outcome. Keith LG, Papiernik E, Keith DM, Luke B (eds). Parthenon: New York, NY, 1995. 145–162. Chmait RH, Floyd R, Benirschke K. Duplicity. Am J Obstet Gynecol 2011; 205: 87.e1–2. Quintero R, Kontopoulos EV, Barness E, Steffensen TS, Hilbelink D, Chmait RH, Benirschke K, Bornick PW. Twin-twin transfusion syndrome in a dichorionic-monozygotic twin pregnancy: the end of a paradigm? Fetal Pediatr Pathol 2010; 29: 81–88. Lee KJ, Kim MK, Lee SY, Lee WS, Lee YH. Spontaneous rupture of the dividing membrane in a monochorionic pregnancy resulting in a pseudo-monoamniotic pregnancy with cord entanglement. J Obstet Gynecol Res 2012; 38: 863–866. Jeanty C, Newman E, Jeanty P, Rodts-Palenik S. Prenatal diagnosis of spontaneous septostomy in dichorionic diamniotic twins and review of the literature. J Ultrasound Med 2010; 29: 455–463. Breathnach FM, McAuliffe FM, Geary M, Daly S, Higgins JR, Dornan J, Morrison JJ, Burke G, Higgins S, Manning F, Caroll S, Malone FD; Perinatal Ireland Research Consortium. Optimum timing for planned delivery of uncomplicated monochorionic and dichorionic twin pregnancies. Obstet Gynecol. 2012; 119: 50–59.
Ultrasound Obstet Gynecol 2014; 44: 722–724.
