Most triploid fetuses are lost during the first trimester due to spontaneous abortion. The fetuses that do survive into the second trimester are usually have a wide range of anatomic defects of the head, face heart and extremities, as well as severe asymmetrical growth restriction (1).

A triploid karyotype is present in 90% of cases with partial mole (2-4).

Studies suggest that the maternal contribution to the zygote is essential for normal embryonal growth and development, while the paternal contribution is essential for proliferation of extraembryonic tissue (6).

Two phenotypes are described (depending on the parental origin of the extra haploid set) (7,8):


Gestational age by dates = 17 wks

GA by ultrasound = 13 wks

Large cystic placenta

Gestational age by dates = 16wks

GA by ultrasound = 12 wks

Large cystic placenta

Triploidy (type II)

  • Placentomegaly.
  • Growth retarded fetus (18 wks by dates).
  • Flexion deformities.



Complications (9) – over 40% of patients are at risk for preeclampsia and a single report of HELLP syndrome has been described).



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  2. Vassilakos P, Riotton G, Kajii T. Hydatidiform mole: Two entities. A morphologic and cytogenetic study with some clinical considerations. Am J Obstet Gynecol 1977;127:167-170.
  3. Szulman AE, Surti U. The syndromes of hydatidiform mole. I. Cytogenetic and morphologic correlations. Am J Obstet Gynecol 1978;131:665-671.
  4. Szulman AE, Surti U. The syndromes of hydatidiform mole. II. Morphologic evolution of the complete and partial mole. Am J Obstet Gynecol 1978;132:22-27.
  5. Lindor NM, Ney JA, Gaffey TA A genetic review of complete and partial hydatidiform moles and nonmolar triploidy. Mayo Clin Proc 1992;67:791-799.
  6. Surani MAH, Barton SC, Norris ML. Nuclear transplantation in the mouse: Hereditable differences between prenatal genomes after activation of the embryonic genome. Cell 1986;45:127-136.
  7. McFadden DE, Kwong LC, Yam IYL Prenatal origin of triploidy in human fetuses: Evidence from genomic imprinting. Hum Genet 1993;92:465-469.
  8. Janiaux E, Brown R, Rodeck C Prenatal diagnosis of triploidy during the second trimester of pregnancy. Obstet Gynecol 1996;88:983-989.
  9. Stefos T, Plachouras N, Mari G A case of partial mole pregnancy and atypical type I triploidy associated wth sever HELLP syndrome at 18 weeks of gestation. Ultrasound Obstet Gynecol 2002;20:403-404.