What Is Triploidy?
Triploidy is a rare chromosomal abnormality. Fetuses with Triploidy, or
Triploid Syndrome, have an extra set of chromosomes in their cells.
One set of chromosomes has 23 chromosomes and is called a haploid set.
Two sets, or 46 chromosomes, are called a diploid set. Three sets, or 69
chromosomes, are called a triploid set.
Typical cells have 46 chromosomes, 23 inherited from the mother and 23
inherited from the father. Fetuses with Triploidy inherit an extra set of
chromosomes from one of the parents.
Triploidy is a lethal condition. Fetuses with the abnormality rarely
survive to birth. Many are spontaneously miscarried during the first trimester
or stillborn before reaching full-term. The few infants that do survive to term
will have severe and multiple birth defects. These might include growth
retardation, heart defects, and neural tube defects (Spina bifida). Infants
born with Triploidy typically will not live more than a few days after
What Causes Triploidy?
Triploidy is the result of an extra set of chromosomes. This can be the
result of two sperm fertilizing one normal egg. It can also occur if a normal
sperm fertilizes an egg that has an extra set of chromosomes.
Who Is at Risk for Triploidy?
Triploidy occurs in one to two percent of all conceptions. There are no
risk factors. Triploidy is not more common in older mothers, like some chromosome
abnormalities, such as Down’s syndrome. Couples who have one pregnancy with
Triploidy do not have an increased risk in future pregnancies. Triploidy is
also not hereditary.
What Are the Symptoms of Triploidy?
Pregnant women carrying fetuses with Triploid Syndrome may experience
preeclampsia. Symptoms of this condition include:
- albuminuria (high levels of albumin, a protein,
in the urine)
- edema (swelling)
- hypertension (high blood pressure)
The physical effects of Triploidy in a fetus depend on whether the
extra set of chromosomes came from the father or the mother. Maternally
inherited chromosomes can cause small heads and a placenta that is enlarged and
filled with cysts. Paternally inherited chromosomes can cause severe growth
problems, an enlarged head, and a small placenta that does not have cysts.
Infants with Triploidy who reach the full-term stage and are delivered
often have one or more of these birth defects:
- abdominal wall defects, such as a hole that
causes the intestines to be located outside the body
- abnormal genitalia (in boys)
- cleft lip and cleft palate
- heart defects
- limb abnormalities, such as webbing of the
fingers and toes
- kidney defects, such as cystic kidney
- neural tube defects, such as Spina bifida
- wide-set eyes
The only test that can confirm a suspected Triploidy diagnosis is a
chromosome analysis (karyotype). This test counts the number of chromosomes
present in a fetus’s genes. To perform this test, a doctor will need to obtain
a tissue sample from the fetus. Because the fetus and placenta came from the
same fertilized egg, a doctor can use a sample of the placenta for testing. Additionally,
an amniocentesis can be used to diagnose Triploidy. The doctor extracts
amniotic fluid. The sample will then be analyzed for signs of abnormal
Triploidy can be discovered prenatally, before the baby is born. The
abnormality may be found if a maternal serum screening test is ordered. This
blood test, which is typically performed during the second trimester of
pregnancy, is not designed to detect the condition. But it may alert an obstetrician
to a potential problem because of other unusual results within the test. Specifically,
too much or too little of certain proteins in the blood may signal an abnormal
pregnancy. If a serum screening test is problematic, additional tests may be
Triploidy can also be discovered during a sonogram or ultrasound. This
imaging test is commonly done during pregnancy to examine the fetus.
Triploidy cannot be treated or cured. Pregnancies that last until the
baby is delivered are rare. In the event an infant does survive, doctors and
healthcare providers usually provide palliative care. Medicinal and surgical
treatments are not used due to the ultimate lethal nature of the condition.
If doctors discover Triploidy while a woman remains pregnant, she has
the option to terminate the pregnancy or carry it to term or until a
spontaneous miscarriage occurs. If she elects to carry the baby to term, she
should be monitored closely for complications caused by Triploidy. These can