Donald School Journal of Ultrasound in Obstetrics and Gynecology

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VOLUME 18 , ISSUE 2 ( April-June, 2024 ) > List of Articles


Prenatal Diagnosis of Conjoined Fetuses

Apostolos Athanasiadis, Panayiota Papasozomenou, Themistoklis Mikos, Menelaos Zafrakas

Keywords : Conjoined triplets, Conjoined twins, Fetal echocardiography, Magnetic resonance imaging, Prenatal diagnosis, Surgical separation, Three-dimensional ultrasound

Citation Information : Athanasiadis A, Papasozomenou P, Mikos T, Zafrakas M. Prenatal Diagnosis of Conjoined Fetuses. Donald School J Ultrasound Obstet Gynecol 2024; 18 (2):199-208.

DOI: 10.5005/jp-journals-10009-2025

License: CC BY-NC 4.0

Published Online: 21-06-2024

Copyright Statement:  Copyright © 2024; The Author(s).


Conjoined twins have an estimated prevalence between one in 50,000 and one in 1,00,000 births. Prenatal two- and three-dimensional (2D and 3D) real-time ultrasonography is the most reliable method for establishing a prenatal diagnosis and detecting associated anomalies. Recent improvements in ultrasonography have made early diagnosis of conjoined fetuses in the first trimester possible. Most cases of conjoined twins occur in monochorionic monoamniotic pregnancies, making sonographic identification of distinct placentae and/or intervening amniotic membrane(s) a criterion to exclude fetal conjunction. There are two opposing pathogenetic theories, supporting fission vs fusion of embryos in the early first trimester. In very rare cases of diamniotic monochorionic conjoined twins, a distinct pathogenetic mechanism of conjoined twinning, similar to that of body stalk anomaly may exist. Prenatal diagnosis of conjoined fetuses is essential for further management. Parents need detailed counseling in order to decide among various management options—(1) pregnancy continuation and scheduled neonatal surgery, (2) termination of pregnancy, and (3) multifetal pregnancy reduction or selective fetocide in cases of high-order multifetal pregnancies with a component of conjoined fetuses. Pre- and postnatal management is challenging, and an interdisciplinary medical team involving obstetricians, neonatologists, pediatric surgeons, and anesthetists should carefully approach and assist parents in their decisions. In special cases, additional consultation by specialized centers in other countries may be needed. Furthermore, adequate psychosocial support should be offered, and palliative care services should be available in selected cases.

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  1. Guttmacher AF. Biographical Notes on some famous conjoined twins. Birth Defects 1967;3:10–17.
  2. van den Brand SF, Nijhuis JG, van Dongen PWJ. Prenatal ultrasound diagnosis of conjoined twins. Obstet Gynecol Survey 1994;49(9):656–662. DOI: 10.1097/00006254-199409000-00028
  3. Harper RG, Kenigsberg K, Sia CG, et al. Xiphopagus conjoined twins: a 300 year review of the obstetric, morphopathologic, neonatal, and surgical parameters. Am J Obstet Gynecol 1980;137(5):617–629. DOI: 10.1016/0002-9378(80)90707-3
  4. Melin JR. Intrapartum diagnosis of conjoined twins. Obstet Gynecol 1967;29(1):50–53. PMID: 6017944.
  5. Gray CH, Nix HG, Wallace AJ. Thoracopagus twins: prenatal diagnosis. Radiology 1950;54(3):398. DOI: 10.1148/54.3.398
  6. Barth RA, Filly RA, Goldberg J, et al. Conjoined twins: prenatal diagnosis and assessment of associated malformations. Radiology 1990;177(1):201–207. DOI: 10.1148/radiology.177.1.2204966
  7. Wilson RL, Cetrulo CL, Shaub MS. The prepartum diagnosis of conjoined twins by the use of diagnostic ultrasound. Am J Obstet Gynecol 1976;126(6):737. DOI: 10.1016/0002-9378(76)90536-6
  8. Fagan CJ. Antepartum diagnosis of conjoined twins by ultrasonography. Am J Roentgenol 1977;129(5):921–922. DOI: 10.2214/ajr.129.5.921
  9. Morgan CL, Trought WS, Sheldon G, et al. B-scan and real-time ultrasound in the antepartum diagnosis of conjoined twins and pericardial effusion. AJR Am J Roentgenol 1978;130(3):578–580. DOI: 10.2214/ajr.130.3.578
  10. Wood MJ, Thompson HE, Roberson FM. Real-time ultrasound diagnosis of conjoined twins. J Clin Ultrasound 1981;9(4):195–197. DOI: 10.1002/jcu.1870090409
  11. Schmidt W, Heberling D, Kubil F. Antepartum ultrasonographic diagnosis of conjoined twins in early pregnancy. Am J Obstet Gynecol 1981;139(8):961–963. DOI: 10.1016/0002-9378(81)90969-8
  12. Schmidt W, Kubli F. Early diagnosis of severe congenital malformations by ultrasonography. J Perinat Med 1982;10(5):233–241. DOI: 10.1515/jpme.1982.10.5.233
  13. Skupski DW, Streltzoff J, Hutson JM, et al. Early diagnosis of conjoined twins in triplet pregnancy after in vitro fertilization and assisted hatching. J Ultrasound Med 1995;14(8):611–615. DOI: 10.7863/jum.1995.14.8.611
  14. Hill LM. The sonographic detection of early first-trimester conjoined twins. Prenatal Diagnosis 1997;17(10):961–963. PMID: 9358576.
  15. Lam YH, Sin SY, Lam C, et al. Prenatal sonographic diagnosis of conjoined twins in the first trimester: two case reports. Ultrasound Obstet Gynecol 1998;11(4):289–291. DOI: 10.1046/j.1469-0705.1998.11040289.x
  16. Goldberg Y, Ben-Shlomo I, Weiner E, et al. First trimester diagnosis of conjoined twins in a triplet pregnancy after IVF and ICSI: case report. Hum Reprod 2000;15(6):1413–1415. DOI: 10.1093/humrep/15.6.1413
  17. Daskalakis G, Pilalis A, Tourikis I, et al. First trimester diagnosis of dicephalus conjoined twins. Eur J Obstet Gynecol Reprod Biol 2004;112(1):110–113. DOI: 10.1016/s0301-2115(03)00268-9
  18. Watanabe K, Ono M, Shirahashi M, et al. Dicephalus parapagus conjoined twins diagnosed by first-trimester ultrasound. Case Rep Obstet Gynecol 2016;2016:8565193. DOI: 10.1155/2016/8565193
  19. Mackenzie TC, Crombleholme TM, Johnson MP, et al. The natural history of prenatally diagnosed conjoined twins. J Pediatr Surg 2002;37(3):303–309. DOI: 10.1053/jpsu.2002.30830
  20. Athanasiadis AP, Tzannatos C, Mikos T, et al. A unique case of conjoined triplets. Am J Obstet Gynecol 2005;192(6):2084–2087. DOI: 10.1016/j.ajog.2004.10.622
  21. Tan KL, Tock EPC, Dawood MY, et al. Conjoined twins in a triplet pregnancy. Am J Dis Child 1971;122(5):455–458. DOI: 10.1001/archpedi.1971.02110050125022
  22. Sepulveda W, Munoz H, Alcalde JL. Conjoined twins in a triplet pregnancy: early prenatal diagnosis with three-dimensional ultrasound and review of the literature. Ultrasound Obstet Gynecol 2003;22(2):199–204. DOI: 10.1002/uog.185
  23. Liu H, Deng C, Hu Q, et al. Conjoined twins in dichorionic diamniotic triplet pregnancy: a report of three cases and literature review. BMC Pregnancy Childbirth 2021;21(1):687. DOI: 10.1186/s12884-021-04165-x
  24. Hanson JW. Incidence of conjoined twining. Lancet 1975;2(7947):1257. DOI: 10.1016/s0140-6736(75)92092-9
  25. Edmonds LD, Layde PM. Conjoined twins in the United States, 1970–1977. Teratology 1982;25(3):301–308. DOI: 10.1002/tera.1420250306
  26. Viljoen DL, Nelson MM, Beighton P. The epidemiology of conjoined twinning in Southern Africa. Clin Genet 1983;24(1):15–21. DOI: 10.1111/j.1399-0004.1983.tb00062.x
  27. Mutchinick OM, Luna-Muñoz L, Amar E, et al. Conjoined twins: a worldwide collaborative epidemiological study of the International Clearinghouse for Birth Defects Surveillance and Research. Am J Med Genet C Semin Med Genet 2011;157C(4):274–287. DOI: 10.1002/ajmg.c.30321
  28. Spencer R. Theoretical and analytical embryology of conjoined twins: part I: embryogenesis. Clin Anat 2000;13(1):36–53. DOI: 10.1002/(SICI)1098-2353(2000)13:1<36::AID-CA5>3.0.CO;2-3
  29. Apuzzio JJ, Ganesh V, Landau I, et al. Prenatal diagnosis of conjoined twins. Am J Obstet Gynecol 1984;148(3):343–344. DOI: 10.1016/s0002-9378(84)80085-x
  30. Zeng SM, Yankowitz J, Murray JC. Conjoined twins in a monozygotic triplet pregnancy: prenatal diagnosis and X-inactivation. Teratology 2002;66(6):278–281. DOI: 10.1002/tera.10091
  31. Steinman G. Mechanisms of twinning. V. Conjoined twins, stem cells and the calcium model. J Reprod Med 2002;47(4):313–321. PMID: 12012884.
  32. Alikani M, Noyes N, Cohen J, et al. Monozygotic twinning in human is associated with zona pellucida architecture. Hum Reprod 1994;9(7):1318–1321. DOI: 10.1093/oxfordjournals.humrep.a138701
  33. Edwards RG, Mettler L, Walters DE. Identical twins and in vitro fertilization. J In Vitro Fert Embryo Transf 1986;3(2):114–117. DOI: 10.1007/BF01139357
  34. Magdi Y. Dizygotic twin from conjoined oocytes: a case report. J Assist Reprod Genet 2020;37(6):1367–1370. DOI: 10.1007/s10815-020-01772-z
  35. Mankonen H, Seikkula J, Järvenpää T, et al. A case of conjoined twins after a transfer of a multinuclear embryo. Clin Case Rep 2015;3(4):260–265. DOI: 10.1002/ccr3.208
  36. Pajkrt E, Jauniaux E. First-trimester diagnosis of conjoined twins. Prenat Diagn 2005;25(9):820–826. DOI: 10.1002/pd.1267
  37. Xiang G, Wen Y, Zhang L, et al. Three-dimensional ultrasonographic features of diamniotic conjoined twins with body stalk anomaly. BMC Pregnancy Childbirth 2020;20(1):221. DOI: 10.1186/s12884-020-02920-0
  38. Kapur RP, Jack RM, Siebert JR. Diamniotic placentation associated with omphalopagus conjoined twins: implications for a contemporary model of conjoined twinning. Am J Med Genet 1994;52(2):188–195. DOI: 10.1002/ajmg.1320520213
  39. Wielgos M, Bomba-Opon D, Kociszewska-Najman B, et al. Minimally conjoined monochorionic diamniotic twins - a case report. Eur J Obstet Gynecol Reprod Biol 2014;180:206–207. DOI: 10.1016/j.ejogrb.2014.06.032
  40. Weston PJ, Ives EJ, Honore RL, et al. Monochorionic diamniotic minimally conjoined twins: a case report. Am J Med Genet 1990;37(4):558–561. DOI: 10.1002/ajmg.1320370428
  41. Karnak I, Sanlialp I, Ekinci S, et al. Minimally conjoined omphalopagi: emphasis on embryogenesis and possibility of emergency separation. Turk J Pediatr 2008;50(5):503–508.
  42. Tihtonen K, Lagerstedt A, Kirkinen M, et al. Diamniotic omphalopagus conjoined twins in a diamniotic pregnancy. Fetal Diagn Ther 2009;25(3):343–345. DOI: 10.1159/000235882
  43. Costa SL, Dunn L, Pantazi S, et al. A novel case of monochorionic diamniotic conjoined twins with genitourinary and gastrointestinal union. Ultrasound Obstet Gynecol 2006;28(4):562–563. DOI: 10.1002/uog.3589
  44. DeStephano CC, Meena M, Brown DL, et al. Sonographic diagnosis of conjoined diamniotic monochorionic twins. Am J Obstet Gynecol 2010;203(6):e4–e6. DOI: 10.1016/j.ajog.2010.09.007
  45. Maruyama H, Inagaki T, Nakata Y, et al. Minimally conjoined omphalopagus twins with a body stalk anomaly. AJP Rep 2015;5(2):e124–e128. DOI: 10.1055/s-0035-1549300
  46. Shah N. Monochorionic diamniotic conjoined twins: prenatal sonographic diagnosis at 8 weeks. Ultrasound Obstet Gynecol 2019;54(5):699–700. DOI: 10.1002/uog.20249
  47. Chatterjee MS, Weiss RR, Verma UL, et al. Prenatal diagnosis of conjoined twins. Prenat Diagn 1983;3(4):357–361. DOI: 10.1002/pd.1970030415
  48. Hubinont C, Pratola D, Rotschild E, et al. Dicephalus: unusual case of conjoined twins and its prepartum diagnosis. Am J Obstet Gynecol 1984;149(6):693–694. DOI: 10.1016/0002-9378(84)90265-5
  49. Kalchbrenner M, Weiner S, Templeton J, et al. Prenatal ultrasound diagnosis of thoracopagus conjoined twins. J Clin Ultrasound 1987;15(1):59–63. DOI: 10.1002/jcu.1870150112
  50. MacKenzie AP, Stephenson CD, Funai EF, et al. Three-dimensional ultrasound to differentiate epigastric heteropagus conjoined twins from a TRAP sequence. Am J Obstet Gynecol 2004;191(5):1736–1739. DOI: 10.1016/j.ajog.2004.01.012
  51. Burans C, Smulian JC, Rochon ML, et al. 3-dimensional ultrasound assisted counseling for conjoined twins. J Genet Couns 2014;23(1):29–32. DOI: 10.1007/s10897-013-9623-1
  52. Athanasiadis A, Mikos T, Zafrakas M, et al. Prenatal management and postnatal separation of omphalopagus and craniopagus conjoined twins. Gynecol Obstet Invest 2007;64(1):40–43. DOI: 10.1159/000098885
  53. Blum E, Pearlman M, Graham D. Early second-trimester sonographic diagnosis of thoracopagus twins. J Clin Ultrasound 1986;14(3):207–208. DOI: 10.1002/jcu.1870140310
  54. Scharl A, Schlensker KH, Wohlers W, et al. Fruhe ultraschall-diagnose des thorakopagus. Z Geburtshilfe Perinatol 1988;192(1):38–41.
  55. Filler RM. Conjoined twins and their separation. Semin Perinatol 1986;10(1):82–91. PMID: 3764451.
  56. Iura T, Makinoda S, Sasakura C, et al. Hemodynamic analysis of cephalothoracopagus by the color Doppler method. A comparison to normal fetuses via a longitudinal study. Fetal Diagn Ther 2006;21(1):61–64. DOI: 10.1159/000089049
  57. Hecht C, Baumann M, Spinelli M, et al. Umbilical cord in conjoined twins: prenatal imaging and anatomopathological aspects. Ultrasound Obstet Gynecol 2019;53(2):269–270. DOI: 10.1002/uog.20095
  58. Razavi-Encha F, Mulliez N, Benhaiem-Sigaux N, et al. Cardiovascular abnormalities in thoracopagus twins: embryological interpretation and review. Early Hum Dev 1987;15(1):33–44. DOI: 10.1016/0378-3782(87)90098-3
  59. Synhorst D, Matlak M, Roan Y, et al. Separation of conjoined thoracopagus twins joined at the right atria. Am J Cardiol 1979;43(3):662–665. DOI: 10.1016/0002-9149(79)90029-8
  60. Rimawi BH, Krishna I, Sahu A, et al. Pregnancy in a previously conjoined thoracopagus twin with a crisscross heart. Case Rep Obstet Gynecol 2015;2015:594537. DOI: 10.1155/2015/594537
  61. Andrews RE, McMahon CJ, Yates RW, et al. Echocardiographic assessment of conjoined twins. Heart 2006;92(3):382–387. DOI: 10.1136/hrt.2005.069682
  62. Sanders SP, Chin AJ, Parness IA, et al. Prenatal diagnosis of congenital heart defects in thoracoabdominally conjoined twins. N Engl J Med 1985;313(6):370–374. DOI: 10.1056/NEJM198508083130607
  63. Boer LL, Schepens-Franke AN, Winter E, et al. Characterizing the coalescence area of conjoined twins to elucidate congenital disorders in singletons. Clin Anat 2021;34(6):845–858. DOI: 10.1002/ca.23725
  64. Bianchi DW, Crombleholme TM. Fetology: Diagnosis and Management of the Fetal Patient. New York: McGraw Hill; 2000. pp. 892–899.
  65. Gao J, Gao YF. Prenatal diagnosis of conjoined twins with real-time ultrasound. Chin Med J (Engl) 1988;101(1):58–60. PMID: 3142735.
  66. Vaughn TC, Powell LC. The obstetrical management of conjoined twins. Obstet Gynecol 1979;53(3 Suppl);67S–72S. PMID: 424132.
  67. Hammond DI, Okun NB, Carpenter BF, et al. Prenatal ultrasonographic diagnosis of dicephalus conjoined twins. Can Assoc Radiol J 1991;42(5):357–359. PMID: 1933505.
  68. Sakala EP. Obstetric management of conjoined twins. Obstet Gynecol 1986;67(3 suppl):21S–25S. DOI: 10.1097/00006250-198603001-00007
  69. Pearn J. Bioethical issues in caring for conjoined twins and their parents. Lancet 2001;357(9272):1968–1971. DOI: 10.1016/S0140-6736(00)05070-4
  70. Savulescu J, Persson I. Conjoined twins: philosophical problems and ethical challenges. J Med Philos 2016;41(1):41–55. DOI: 10.1093/jmp/jhv037
  71. Graivier L, Jacoby MD. Emergency separation of newborn conjoined (Siamese) twins. Tex Med 1980;76(10):60–62. PMID: 7434246.
  72. O'Neill JA Jr, Holcomb GW 3rd, Schnaufer L, et al. Surgical experience with thirteen conjoined twins. Ann Surg 1988;208(3):299–312. DOI: 10.1097/00000658-198809000-00007
  73. Chiu CT, Hou SH, Lai HS, et al. Separation of thoracopagus conjoined twins. A case report. J Cardiovasc Surg (Torino) 1994;35(5):459–462. DOI: 10.5402/2011/238360
  74. Spitz L, Kiely E. Success rate for surgery of conjoined twins. Lancet 2000;356(9243):1765. DOI: 10.1016/s0140-6736(00)03220-7
  75. Di Rocco C, Caldarelli M, Tamburrini G, et al. Craniopagus: the Thessaloniki-Rome experience. Childs Nerv Syst 2004;20(8-9):576–586. DOI: 10.1007/s00381-004-0976-5
  76. Thomas A, Johnson K, Placencia FX. An ethically-justifiable, practical approach to decision-making surrounding conjoined-twin separation. Semin Perinatol 2018;42(6):381–385. DOI: 10.1053/j.semperi.2018.07.016
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