NORD gratefully acknowledges Lewis Holmes, MD, Emeritus Unit Chief, Medical Genetics, Pediatric Service, Emeritus Director, Genetic Counseling & Screening Services, Perinatal Diagnostic Unit, Obstetrics Program, Massachusetts General Hospital, for assistance in the preparation of this report.
Triploidy is a rare chromosomal abnormality. Triploidy is the presence of an additional set of chromosomes in the cell for a total of 69 chromosomes rather than the normal 46 chromosomes per cell. The extra set of chromosomes originates either from the father or the mother during fertilization. Pregnancies with triploidy are usually miscarried early in the pregnancy. If the pregnancy continues to term, the infant dies within the first days of life. A few affected individuals have been reported to have survived to adulthood, but suffered from developmental delay, learning difficulties, seizures, hearing loss and other abnormalities. Those that survive have mosaic triploidy, meaning that some cells have the normal number of 46 chromosomes and other cells have 69 chromosomes per cell. Infants affected with complete triploidy suffer from growth restriction and multiple birth defects.
Infants affected with triploidy have heart defects, abnormal brain development, adrenal and kidney defects (cystic kidneys), spinal cord malformations (neural tube defects) and abnormal facial features (widely spaced eyes, low nasal bridge, low-set malformed ears, small jaw, absent/small eye, and cleft lip and palate). The third and fourth fingers of the hands and the second and third toes of the feet may be united and the hands may have unusual simian creases. There may also be liver and gallbladder defects, twisted intestines and deformities of the fingers and toes. The placenta in triploidy may be immature, large, and filled with cysts. Individuals who are mosaic will survive longer than those with complete triploidy but usually have intellectual disability, developmental delay, depression, seizures, short stature, obesity and other abnormalities.
The pregnant mother carrying a triploidy fetus sometimes experiences increase in blood pressure (hypertension), swelling (edema), and excretion of albumin in the urine (albuminuria). This condition is called toxemia or preeclampsia.
Triploidy is the presence of a complete additional set of chromosomes. The triplication of the chromosomes is caused by the fertilization of an egg by two sperms, or the fertilization of an egg by a sperm that has an extra set of chromosomes or by the fertilization of an egg that has an extra set of chromosomes by a normal sperm. This disorder does not run in families and is not associated with maternal or paternal age.
Triploidy accounts for 1-3 percent of all pregnancies. 2/3 of triploid pregnancies are male.
The presence of multiple major malformations, low amniotic fluid and/or growth restriction on fetal ultrasound during pregnancy raises the suspicion of triploidy. The diagnosis can be made during pregnancy by chromosome analysis (karyotyping) of cells obtained by amniocentesis or chorionic villus sampling (CVS). The diagnosis can be confirmed after birth by chromosome analysis of tissue (skin) obtained from the affected infant. Triploidy cannot be diagnosed by chromosome microarray testing. The accuracy of non-invasive prenatal testing using cell-free fetal (cff) DNA in the diagnosis of triploidy is still being studied. Abnormal levels of specific maternal blood proteins such as alpha-fetoprotein, human chorionic gonadotropin, estriol and pregnancy-assisted plasma protein-A have been associated with an increased risk for triploidy.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:
Jones KL, Ed. Smith’s Recognizable patterns of Human Malformation. 4th ed. W.B. Saunders Company. 1998:32-35.
Toufaily MH, Roberts DJ, Westgate MN, Holmes LB. Triploidy: Variation of Phenotype. AM J Clin Pathol. 2016 Jan; 145(1):86-95. doi: 10.1093/ajcp/aqv012
Jewell R, BirchA, Roberts P, et al. Phenotypic features of diploid/triploid mosaicism in an adult. Clin Dysmorphol. 2014;23:56-59
Boonen SE, Hoffman AL, Donnai D, et al. Diploid/triploid mosaicism: a rare event or an under-diagnosed syndrome? Eur J Med Genet. 2011;54:374-375.
Benn PA, et al. Second trimester maternal serum analytes in triploid pregnancies: correlation with phenotype and sex chromosome complement. Prenat Diag. 2001;21:680-686.
Carp H, et al. Karyotype of the abortus in recurrent miscarriage. Fertil Steril 2001;75:678-682.
Zaragoza MV et al. Parental origin and phenotype of triploidy in spontaneous abortions: predominance of diandry and association with the partial hydatidiform mole. Am J Hum Genet. 2000;66:1807-1820.
Cerakushansky G, et al. Diploid/triploid mosacicism: Further delination of the phenotype. Am J Med Genet. 1994;52:399-401.
Graham JM, et al. Triploidy: Pregnancy complications and clinical findings in seven cases. Prenat Diag. 1989;9:409-19.
Edwards MJ, et al. Clinical features of diploid/polyploid mixoploidy in older individuals. Pediat Res. 1989;25:76.
Angell RR, et al. Chromosome studies in human in vitro fertilization. Hum Genet. 1986;72:333-339.
Doshi N, et al. Morphologic anomalies in triploid liveborn fetuses. Hum Path. 1983;14(4):716-723.
Graham JM, et al. Diploid-Triploid mixoploidy: Clinical and cytogenetic aspects. Pediatrics. 1981;68:23-8.
Beatty RA. The origin of human triploidy: An integration of qualitative and quantitative evidence. Ann Hum Genet (Cambridge). 1978;41:229-314.
Wertelecki W, et al. The clinical syndrome of triploidy. Obst Gyn. 1976;47:69-76.
Holland, Kimberly. Triploidy. Healthline. http://www.healthline.com/health/triploidy Last UpdateJuly 8, 2017. Accessed August 31, 2020.
Triploidy Rare Chromosome Disorder Support Group. Last Update 2005. https://www.rarechromo.org/media/information/Other%20Topics/Triploidy%20FTNP.pdf Accessed September 2, 2020.
The information in NORD’s Rare Disease Database is for educational purposes only and is not intended to replace the advice of a physician or other qualified medical professional.
The content of the website and databases of the National Organization for Rare Disorders (NORD) is copyrighted and may not be reproduced, copied, downloaded or disseminated, in any way, for any commercial or public purpose, without prior written authorization and approval from NORD. Individuals may print one hard copy of an individual disease for personal use, provided that content is unmodified and includes NORD’s copyright.
National Organization for Rare Disorders (NORD)
55 Kenosia Ave., Danbury CT 06810 • (203)744-0100