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Last updated: 5/13/2024
Years published: 1989, 2003, 2016, 2020, 2024
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.
Summary
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 comes 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. Infants affected with complete triploidy have growth restriction and multiple birth defects. A few affected individuals have been reported to have survived to adulthood, but had developmental delay, learning difficulties, seizures, hearing loss and other abnormalities. Individuals who survive have mosaic triploidy, meaning that some cells have the normal number of 46 chromosomes and other cells have 69 chromosomes per cell.
Most fetuses (unborn babies) affected with triploidy are spontaneously miscarried early in the pregnancy. If the pregnancy continues to term, the baby dies within the first days of life. Infants affected with complete triploidy have the following signs and symptoms:
The placenta in triploidy may be immature, large and filled with cysts (molar pregnancy). 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 fetus with triploidy sometimes has high blood pressure (hypertension), swelling (edema) and excretion of albumin in the urine (albuminuria). This condition is called toxemia or preeclampsia.
Anomalies of the amniotic fluid volume, the fluid that surrounds the baby in the uterus, can be present, such polyhydramnios, the buildup of increased amniotic fluid or olygohydramnius, a decreased amniotic fluid which is a frequent finding in mid pregnancy.
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.
When the extra haploid set of chromosomes from father is involved, the triploidy is called diandric and when it is from mother, it is called digynic. Based on the parental origin of triploidy, it is grouped into two types.
A molar pregnancy is a rare complication of pregnancy. It involves unusual growth of cells called trophoblasts. These cells typically become the organ that feeds a growing fetus, also known as the placenta. There are two types of molar pregnancy, complete molar pregnancy and partial molar pregnancy. In a complete molar pregnancy, the placental tissue swells and appears to form fluid-filled cysts and there is no fetus. In a partial molar pregnancy, the placenta might have both regular and irregular tissue. There may be a fetus, but the fetus usually miscarried early in the pregnancy.
It is important to establish which parent contributed the extra chromosomes to the pregnancy because of the link with a partial molar pregnancy. Partial molar pregnancies are not found when the extra chromosomes are from the mother, but they may be found when the chromosomes are paternal (diandric).
Women who have had a molar pregnancy need to be followed up to ensure that there is no abnormal tissue left. Remnants of mole tissue can grow and carry a small risk of developing into a form of cancer called choriocarcinoma. This is treatable and the aim of follow-up is to ensure that if it does develop it is caught and treated as early as possible. Follow-up is usually for six months to two years.
Triploidy occurs in about 1-3% of all pregnancies. About 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.
Treatment
Treatment of triploid syndrome is symptomatic and supportive. As commented before, more babies die when they are still in the womb or are stillborn.
As commented before, a molar pregnancy can have serious complications, including a rare form of cancer and requires follow-up and early treatment.
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: https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact: www.centerwatch.com
For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
TEXTBOOKS
Jones KL, Ed. Smith’s Recognizable patterns of Human Malformation. 4th ed. W.B. Saunders Company. 1998:32-35.
JOURNAL ARTICLES
Jadhav A, Jadhav Y, Bhairi V, Ansari R, Torane P, Patil K. Prenatal diagnosis of triploidy in fetus with unexpected chromosomal translocation of maternal origin. Int J Mol Cell Med. 2023;12(1):81-85. doi:10.22088/IJMCM.BUMS.12.1.81
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.
INTERNET
Triploidy. Unique. Last Update 2005. https://www.rarechromo.org/media/information/Other%20Topics/Triploidy%20FTNP.pdf Accessed Feb 26, 2024.
Molar pregnancy. Mayo Clinic. November 12, 2022. https://www.mayoclinic.org/diseases-conditions/molar-pregnancy/symptoms-causes/syc-20375175 Accessed May 13, 2024.
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The Genetic and Rare Diseases Information Center (GARD) has information and resources for patients, caregivers, and families that may be helpful before and after diagnosis of this condition. GARD is a program of the National Center for Advancing Translational Sciences (NCATS), part of the National Institutes of Health (NIH).
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