Triploidy is a rare condition that occurs when there are three or more chromosomes in the cell nucleus of an embryo. It affects approximately 1 out of every 500,000 live births (1). It causes several health problems, including heart defects, mental retardation and blindness. There is no cure for triploidy. The only treatment option is to have the embryos destroyed (2).
The term “triploid” refers to having 3 or more sets of chromosomes instead of two. The word “ectopic” means outside the normal range of development. Ectopic pregnancies occur when an egg develops outside its usual place in the fallopian tube and implants somewhere else (3).
In the case of triploidy, it is not possible to distinguish between a normal embryo and one with extra chromosomes. When the number of chromosomes reaches 21, the embryo becomes an ectopic pregnancy (4). The chances of conception increase significantly if the fertilized egg contains at least 2 extra copies of chromosome 21 (5).
If the eggs develop normally, then both will implant into their intended womb. If an egg contains extra copies of chromosome 21, then it will not be able to implant into the womb.
If the embryo is triploid, it can not develop into a fetus and will cause an early miscarriage (6). Ectopic pregnancies are most common during the first three months of gestation (7). As a result, many pregnancies that were conceived with extra chromosomes result in miscarriages.
The average age of women who get pregnant with a triploid child is 25 years (8).
The age of the mother is not the only risk factor for a triploid pregnancy. A risk factor for all pregnancies is having a uterine abnormality. A uterine abnormality tends to prevent a fertilized egg from implanting into the uterus.
If it can not implant, then it can not develop into a fetus. Removing the fallopian tubes eliminates the risk of an ectopic pregnancy.
Pregnancies that have a high risk of an ectopic pregnancy are not suitable for treatment with assisted reproductive technology (9). This includes women who have had previous ectopic pregnancies and those who have had their fallopian tubes removed. It also includes women with a history of congenital uterine abnormalities or cervical cancer.
However, the risk of a triploid pregnancy is extremely low in these cases (10).
In order to prevent an ectopic pregnancy, you should limit the time you spend sitting. If you are overweight, you should try to lose weight. You can help prevent an ectopic pregnancy by drinking 8 or more glasses of water each day and practicing stress reduction techniques (11).
The age of the mother increases the risk of a triploidy pregnancy. The average age of mothers who have a child with triploidy is 25 years old. During the first 3 months of pregnancy, you should see your physician on a regular basis.
This can help detect problems early and allow for the termination of the pregnancy (12).
There are several ways to test for triploidy in both parents and the fetus. These tests are usually performed during the second trimester of pregnancy.
One method is a combined maternal serum and fetal nasal swab (13). Maternal serum refers to testing the mothers blood for fetal DNA and hormones. This test can be done as early as week 8 of the pregnancy.
The nasal swab involves taking a cotton swab from the upper part of the fetus’s nose. It can be done as early as week 10 of the pregnancy. The blood is taken from the arm and then sent to a lab to be tested.
Another method is an ultrasound exam of the fetus (14). The ultrasound can be done in the 1st, 2nd, or 3rd trimester. It uses sound waves to make images of the fetus on a monitor.
This test can show physical abnormalities in the fetus.
A third method is called amniocentesis (15). This is where a needle is inserted into the uterus to remove amniotic fluid. The fetal cells can then be tested for chromosomal abnormalities.
It can be performed any time after week 13.
A final method of testing is chorionic villus sampling (16). This involves taking a small sample of the placenta and testing it for chromosomal abnormalities. It can be performed in the 10th or 11th week of pregnancy.
There are several risks to these tests. One risk is that the fetus could be lost during the procedure. Another risk is that the procedure may result in a miscarriage (17).
It has been reported that 1 out of every 40 women with a triploid fetus has an ectopic pregnancy (18). Ectopic pregnancies can be life-threatening if not treated. It is important to seek medical care at the earliest signs of an ectopic pregnancy (see warning signs).
Once a triploid fetus has been detected, there are two options that may be considered. The first is the termination of the pregnancy. This should be discussed with your physician.
The second option is intrauterine fetal surgery (19). During this procedure, a needle is used to remove amniotic fluid from the sac surrounding the fetus. A small hole is then made in the sac and the fluid is drained out.
A larger incision is made and the fetus’s organ are subjected to a small electric shock. This procedure opens up blood vessels that were previously not working. The hole in the amniotic sac is then repaired with a glue-like substance and the fluid is replaced.
The success rate of this procedure depends on the location of the triploid area within the fetus (20). This is why the testing is so important.
In certain situations, a combination of both procedures may be recommended (21).
It has been suggested that an imbalance of maternal hormones during pregnancy increases the risk of having a baby with a chromosome abnormality (22). Taking special vitamins and minerals during the first trimester may help to reduce this risk. Speak to your physician before taking any supplements.
People have different ideas about what quality of life a person should have. Some feel that any quality of life is better than no life at all. Others feel that life, even if not ideal, is still worth living.
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The outlook for children with trisomy 18 or 13 varies depending on the specific problem(s) they have. Some children with trisomy 18 are stillborn, while others may survive for a few hours up to one or two years. Children with trisomy 13 tend to have even shorter life spans than those with trisomy 18.
Some infants with trisomy 18 or 13 die because of problems with their underdeveloped organs (23).
Other infants and children die from heart defects, weak muscles, recurring respiratory infections, and digestive system problems. These children may also have behavioral and learning problems (24).
Of children with trisomy 18, 30% live at least one year. Of children with trisomy 13, 10-30% live at least one year (25).
The youngest child ever to have trisomy 18 was a 8 day old baby who died from heart failure. The youngest child ever to have trisomy 13 was a 6 day old baby who died from heart failure (26).
Life expectancy for people with trisomy 18 or 13 is usually 5-8 years (27). Some people with these syndromes may survive into their teens.
Most babies with trisomy 13 are stillborn or die within a few hours or days after birth. Of those that do survive, life spans vary. A few may live into their teens (28).
Life expectancy also varies according to which specific chromosome(s) are involved. People with partial trisomy 13 may have normal life expectancies, provided they receive regular check-ups and monitoring for heart problems.
Trisomy 16 is another chromosome abnormality that can affect a fetus. It occurs when there are three number 16 chromosomes rather than two, resulting in 69 chromosomes rather than the usual 46. Like trisomy 13 and 18, it occurs in approximately 1 in every 5000 births.
Four-year-old Raunaq Patel was diagnosed with trisomy 16 shortly after his birth. At four years of age he shows no sign of any significant medical problems (29).
In another case, a 26 year old Chicago man was diagnosed with trisomy 16 after learning that he had an extra number 16 chromosome. He has been described as being in good health (30).
There are rare cases of people who have both trisomy 13 and 16. One such person, a 29 year old woman, died within 24 hours of her birth (31).
There is no specific treatment for trisomy 13 or 18. Infants and children with these syndromes require regular medical check-ups to monitor their growth and development. They also require special care to help them meet their basic needs and to reduce the risk of life-threatening health problems.
Trisomy 13 and 18 are usually diagnosed before birth, through ultrasound, amniocentesis or chorionic villus sampling (CVS).
Sources & references used in this article:
Triploidy in man by E Niebuhr – Humangenetik, 1974 – Springer
Triploidy and chromosomes by IA Uchida, VCP Freeman – American journal of obstetrics and gynecology, 1985 – Elsevier
Early prenatal diagnosis of triploidy by E Jauniaux, R Brown, RJM Snijders, P Noble… – American journal of …, 1997 – Elsevier
Three cases of triploidy in man by JH Edwards, C Yuncken, DI Rushton… – … and Genome Research, 1967 – karger.com