Guide | Understanding Triploidy: How an Extra Set of Fetal Chromosomes Affects Pregnancy
Triploidy is a rare chromosomal abnormality affecting approximately 1% to 3% of pregnancies. The fetus has an extra complete set of chromosomes. This usually causes early miscarriage; if the pregnancy continues, the baby may have severe birth defects and health problems.
Causes of Triploidy
Human cells normally contain 46 chromosomes arranged in 23 pairs, with half inherited from each parent. In triploidy, the fetus has an additional set, for a total of 69 chromosomes. This can occur when:
Two sperm fertilize one egg.
A sperm containing extra chromosomes fertilizes a normal egg.
An egg containing extra chromosomes is fertilized by a normal sperm.
Risk Factors for Triploidy
No clear risk factors have been identified. Triploidy is not inherited and is unrelated to parental age. Some studies indicate that having one triploid pregnancy does not increase a couple's risk of another.
Symptoms of Triploidy
A baby born with triploidy usually has severe problems involving:
Heart
Brain development
Kidneys
Spinal cord
Liver and gallbladder
Intestines
Distinct physical features may also include:
Widely spaced eyes
Underdeveloped or absent eyes
Flat nasal bridge
Low-set, malformed ears
Small jaw
Cleft lip and palate
Fusion of the third and fourth fingers
Fusion of the second and third toes
Other finger and toe abnormalities
Unusual palm creases
Effects of Triploidy on the Pregnant Woman
Most triploid pregnancies end in early miscarriage. If the pregnancy continues, the woman may develop preeclampsia, with symptoms including:
Swelling of the hands or face
Weight gain of more than 3 to 5 pounds per week
Headache
Dizziness
Irritability
Shortness of breath
Reduced urination
Upper abdominal pain
Nausea or vomiting
Blurred vision or flashing lights
Temporary blindness
These symptoms can also occur with other conditions, so any abnormalities should be discussed promptly with a doctor. Preeclampsia requires treatment because it can threaten both maternal and fetal life.
Diagnosis of Triploidy
Triploidy may be suspected during routine ultrasound when abnormal anatomy, low amniotic fluid, or slow fetal growth is seen. Confirmation may involve:
Amniocentesis: A needle is inserted through the abdomen to collect amniotic fluid.
Chorionic villus sampling: A placental sample is collected through the abdomen with a needle or through the cervix with a tube.
Both tests carry some risk of miscarriage and should be discussed carefully with a doctor.
Triploidy can also be confirmed after birth by analyzing chromosomes in a skin sample. A blood-based microarray cannot diagnose triploidy.
Treatment of Triploidy
There is no cure for triploidy. If a baby is born, care is supportive and focuses on relieving symptoms and maximizing quality of life.
Prognosis
Most infants with triploidy die within days or months after birth. Rare cases survive into adulthood, usually with severe developmental delay, learning disabilities, seizures, and hearing loss. These longer-term survivors generally have mosaic triploidy, meaning some cells contain the normal 46 chromosomes while others contain 69.
Triploidy vs. Trisomy
Although triploidy and trisomy, such as Down syndrome, are both chromosomal abnormalities, they differ fundamentally. Triploidy is an extra copy of the entire chromosome set. Trisomy is one extra copy of a single chromosome, such as chromosome 21 in Down syndrome.
Guide | Understanding Triploidy: How an Extra Set of Fetal Chromosomes Affects Pregnancy
Guide | Understanding Triploidy: How an Extra Set of Fetal Chromosomes Affects Pregnancy
Triploidy is a rare chromosomal abnormality affecting approximately 1% to 3% of pregnancies. The fetus has an extra complete set of chromosomes. This usually causes early miscarriage; if the pregnancy continues, the baby may have severe birth defects and health problems.
Causes of Triploidy
Human cells normally contain 46 chromosomes arranged in 23 pairs, with half inherited from each parent. In triploidy, the fetus has an additional set, for a total of 69 chromosomes. This can occur when:
Two sperm fertilize one egg.
A sperm containing extra chromosomes fertilizes a normal egg.
An egg containing extra chromosomes is fertilized by a normal sperm.
Risk Factors for Triploidy
No clear risk factors have been identified. Triploidy is not inherited and is unrelated to parental age. Some studies indicate that having one triploid pregnancy does not increase a couple's risk of another.
Symptoms of Triploidy
A baby born with triploidy usually has severe problems involving:
Heart
Brain development
Kidneys
Spinal cord
Liver and gallbladder
Intestines
Distinct physical features may also include:
Widely spaced eyes
Underdeveloped or absent eyes
Flat nasal bridge
Low-set, malformed ears
Small jaw
Cleft lip and palate
Fusion of the third and fourth fingers
Fusion of the second and third toes
Other finger and toe abnormalities
Unusual palm creases
Effects of Triploidy on the Pregnant Woman
Most triploid pregnancies end in early miscarriage. If the pregnancy continues, the woman may develop preeclampsia, with symptoms including:
Swelling of the hands or face
Weight gain of more than 3 to 5 pounds per week
Headache
Dizziness
Irritability
Shortness of breath
Reduced urination
Upper abdominal pain
Nausea or vomiting
Blurred vision or flashing lights
Temporary blindness
These symptoms can also occur with other conditions, so any abnormalities should be discussed promptly with a doctor. Preeclampsia requires treatment because it can threaten both maternal and fetal life.
Diagnosis of Triploidy
Triploidy may be suspected during routine ultrasound when abnormal anatomy, low amniotic fluid, or slow fetal growth is seen. Confirmation may involve:
Amniocentesis: A needle is inserted through the abdomen to collect amniotic fluid.
Chorionic villus sampling: A placental sample is collected through the abdomen with a needle or through the cervix with a tube.
Both tests carry some risk of miscarriage and should be discussed carefully with a doctor.
Triploidy can also be confirmed after birth by analyzing chromosomes in a skin sample. A blood-based microarray cannot diagnose triploidy.
Treatment of Triploidy
There is no cure for triploidy. If a baby is born, care is supportive and focuses on relieving symptoms and maximizing quality of life.
Prognosis
Most infants with triploidy die within days or months after birth. Rare cases survive into adulthood, usually with severe developmental delay, learning disabilities, seizures, and hearing loss. These longer-term survivors generally have mosaic triploidy, meaning some cells contain the normal 46 chromosomes while others contain 69.
Triploidy vs. Trisomy
Although triploidy and trisomy, such as Down syndrome, are both chromosomal abnormalities, they differ fundamentally. Triploidy is an extra copy of the entire chromosome set. Trisomy is one extra copy of a single chromosome, such as chromosome 21 in Down syndrome.
Source:
Collected online