Medicine:Triploid syndrome

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Short description: Chromosomal disorder in which there are three copies of every chromosome
Triploid syndrome
Other names69,XXX[1] 2n/3n mixoploidy, 3n syndrome, chromosome triploidy syndrome, diploid/triploid mixoploidy, triploidy, triploidy syndrome
A karyotype of a fetus with triploidy
SpecialtyMedical genetics
Differential diagnosisTrisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome)

Triploid syndrome, also called triploidy, is a chromosomal disorder in which a fetus has three copies of every chromosome instead of the normal two. If this occurs in only some cells, it is called mosaic triploidy and is less severe.

Most embryos with triploidy miscarry early in development.

Signs and symptoms

Many organ systems are affected by triploidy, but the central nervous system and skeleton are the most severely affected:


Skeletal manifestations include cleft lip/palate,[2] hypertelorism, micrognathia,[2] club foot and syndactyly.[3]

Congenital heart defects, hydronephrosis, omphalocele,[2] microphthalmia,[2] macroglossia[2] and meningocele (spina bifida) are also common. Cystic hygromas occur but are uncommon.[4]

Triploid fetuses have intrauterine growth restriction beginning early in the pregnancy, as early as 12 weeks, and does not affect the head as severely as the body. Oligohydramnios, low levels of amniotic fluid, is common in triploid pregnancies. Placental abnormalities are common in triploidy. Most frequently, the placenta is enlarged and may have cysts within. In some cases, the placenta may be unusually small, having ceased to grow.[5]

During the first trimester, fetuses with triploidy have a thicker fluid under the skin behind their neck, which calls for observation during the first and second trimester of gestation.[6][7]

The mother will usually have high levels of specific proteins including maternal serum alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (hCG).[8] Symptoms may include, but are not limited to, swelling, edema, or hypertension.[9]

Infants may show facial abnormalities, micrognathia, cleft lip, spina bifida, as well as other birth defects that result from kidney, limb, and umbilical cord complications. They are also prone to being smaller than a normal sized newborn, a problem that arises while the infant is still a fetus.[10]

Causes

Triploidy is caused by an extra set of chromosomes.[2]

Triploidy can result from diandric fertilization, where either two sperm or a single diploid sperm fertilize one egg (polyspermy) (60%) or digynic fertilization, where from one sperm fertilizes an egg with two copies of every chromosome (40%).[5]

Diagnosis

Triploidy may be suggested by dramatically elevated levels of serum alpha-fetoprotein. On obstetric ultrasonography, abnormalities of the skeleton, central nervous system, heart, abdomen, and kidneys are visible in the most severe cases beginning at 12–14 weeks of pregnancy. Placental abnormalities associated with a triploid pregnancy become visible at 12–14 weeks. Placentomegaly or intrauterine growth restriction are the typical findings that prompt evaluation for triploidy, though oligohydramnios may be the first sign in some cases. Placentomegaly is not pathognomonic for triploidy because in some cases, the placenta senesces.[5]

Triploidy must be distinguished from trisomy 13 and trisomy 18, which may appear similar on sonography. Genetic testing allows for a definitive diagnosis.[5]

A sample of amniotic fluid can also be tested to diagnose triploidy.

Prognosis

Mosaic triploidy has an improved prognosis, but affected individuals have moderate to severe cognitive disabilities.[5]

Epidemiology

Triploidy affects approximately 1–2% of pregnancies, but most miscarry early in development. At birth, males with triploidy are 1.5 times more common than females.[5]

See also

  • Polyploid
  • Diploid triploid mosaic

References

  1. ↑ "Complete chorioamniotic separation and persistence of a yolk sac associated with triploidy". Journal of Obstetrics and Gynaecology Canada 35 (10): 914–6. October 2013. doi:10.1016/S1701-2163(15)30813-6. PMID 24165059. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 "Triploidy - Pediatric Pathology - Work and Learning Resources - Department of Pathology - University of Rochester Medical Center". https://www.urmc.rochester.edu/pathology-labs/work-learning-resources/pediatric-pathology/triploidy. 
  3. ↑ Powell, Cynthia M.; Pandya, Arti; Al Saif, Hind; Babu, Kevin; Couser, Natario L. (2019-01-01), "Chapter 1 - Eye Abnormalities in Patients With Chromosomal Disorders", Ophthalmic Genetic Diseases, Philadelphia: Elsevier, pp. 1–13, doi:10.1016/B978-0-323-65414-2.00001-5, ISBN 978-0-323-65414-2, https://www.sciencedirect.com/science/article/pii/B9780323654142000015, retrieved 2026-07-14 
  4. ↑ Ammari, Roa Al; Kaplan, Jeremy; Wolfberg, Adam; Tanner, Cassandre; Iyer, Chitra; Heard, Asha; Coletta, Jaclyn; Panda, Britta et al. (2011-01-01). "704: Obstetric outcomes in cases of first trimester cystic hygroma" (in English). American Journal of Obstetrics & Gynecology 204 (1): S278–S279. doi:10.1016/j.ajog.2010.10.726. ISSN 0002-9378. https://www.ajog.org/article/S0002-9378(10)01985-X/fulltext. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 Sanders, Roger C. (2002-01-01) (in en). Structural Fetal Abnormalities: The Total Picture. Mosby. ISBN 9780323014762. https://books.google.com/books?id=GeBsAAAAMAAJ. 
  6. ↑ Spencer, K; Liao, A W J; Skentou, H; Cicero, S; Nicolaides, K H (2000). "Screening for triploidy by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation". Prenatal Diagnosis 20 (6): 495–499. doi:10.1002/1097-0223(200006)20:6<495::AID-PD846>3.0.CO;2-U. PMID 10861716. https://www.scopus.com/pages/publications/0034041082. 
  7. ↑ Wagner, P.; Sonek, J.; Hoopmann, M.; Abele, H.; Kagan, K. O. (October 2016). "First-trimester screening for trisomies 18 and 13, triploidy and Turner syndrome by detailed early anomaly scan". Ultrasound in Obstetrics & Gynecology: The Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology 48 (4): 446–451. doi:10.1002/uog.15829. ISSN 1469-0705. PMID 26611869. 
  8. ↑ Dalmia, Ritu; Young, Peter; Sunanda, G. V. (2005-02-01). "A case of triploidy" (in English). Fertility and Sterility 83 (2): 462–463. doi:10.1016/j.fertnstert.2004.07.968. ISSN 0015-0282. PMID 15705393. https://www.fertstert.org/article/S0015-0282(04)02874-2/fulltext. 
  9. ↑ "Triploidy And Its Effect On Maternal Health During Pregnancy - Klarity Health Library" (in en-US). 2025-12-03. https://my.klarity.health/triploidy-and-its-effect-on-maternal-health-during-pregnancy/. 
  10. ↑ Wake Forest Baptist Medical Center; Jln, Holman (2020-03-10). "Multiple Fetal Anomalies: A Case Of Complete Triploidy". Neonatology and Clinical Pediatrics 7 (1): 1–3. doi:10.24966/NCP-878X/100045. https://www.heraldopenaccess.us/openaccess/multiple-fetal-anomalies-a-case-of-complete-triploidy. 
Classification
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