Triploidy

Sadly, This Fatal Chromosomal Disorder Has No Treatment

Woman in Blue Holds Her Pregnant Belly
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Genetic and chromosomal disorders can have a varying and potentially far-reaching impact on a baby's health. The effects can be anything from mild health concerns to being "incompatible with life," meaning a fatal prognosis.

Triploidy is a disorder that falls on the latter end of the spectrum. The majority of fetuses that have triploidy die before birth, and those that make it to term rarely survive the first six months of life.

What Triploidy Means:

Human beings are each supposed to have 46 chromosomes (23 pairs). A person gets half of each pair of chromosomes from each parent. Triploidy means that a baby has three copies of each chromosome in each cell, rather than two, making a total of 69 chromosomes. Triploidy can result either from a single egg being fertilized by two sperm or from an error in cell division that causes either the egg or the sperm to have 46 chromosomes at the time of fertilization.

Types of Triploidy:

Most cases of triploidy involve "full" triploidy, meaning all the body's cells are uniformly affected. In rare cases, the triploidy can be "mosaic," meaning some of the body's cells have three copies of each chromosome and others have a normal set of 46 chromosomes. There is some evidence that individuals that have mosaic triploidy may be less severely affected by the disorder than those with full triploidy.

But even with mosaic triploidy, the prognosis is not good.

The Relationship to Partial Molar Pregnancy:

Some pregnancies affected by triploidy will also be affected by a partial hydatidiform mole (partial molar pregnancy), meaning there is an abnormal placenta that can, in rare cases, cause life-threatening complications for the mother.

However, not every case of triploidy will be a molar pregnancy. There is some suspicion that triploidy resulting from two sperm fertilizing a single egg may be more likely to cause a partial molar pregnancy than triploidy involving an egg or sperm having 46 chromosomes from the start. But this has not been proven.

Diagnosis:

Triploidy can be diagnosed through only genetic testing—meaning amniocentesis, blood testing of a newborn baby, or karyotyping of tissue from a pregnancy loss. Screening tests such as ultrasound and alphafetoprotein testing may show warning signs of triploidy. But these tests cannot confirm a diagnosis of triploidy. Abnormally high hCG levels can be found in some pregnancies with triploidy, and an ultrasound can show the characteristic placenta associated with a partial molar pregnancy.

Prognosis:

Sadly, triploidy is always fatal and there is no cure or treatment for the condition. As mentioned above, almost all (more than 99%) of babies with triploidy are miscarried or stillborn.

Of those born alive, most die in the hours or days following birth. A handful of babies with triploidy have lived five months or longer. But these reports are rare, and usually the babies who survive longer have mosaic triploidy, rather than full triploidy. Affected babies usually have multiple birth defects and severe growth restriction.

Risk of Recurrence:

Researchers have not found any identifiable risk factors for having a pregnancy that's affected by triploidy. Even maternal age does not seem to be a risk factor. A small number of women may have recurrent miscarriages affected by triploidy. But in the majority of cases, triploidy occurs randomly and is a one-time tragedy that does not repeat in future pregnancies. If you have received a triploidy diagnosis following the testing of tissue from a miscarriage or stillbirth, the odds of it happening again are slim.

If Your Baby Has Triploidy:

A lot of confusing information about triploidy is out there, so if your baby has been diagnosed with this condition during pregnancy or as a newborn, you are likely swimming with emotions, including numbness, confusion, and grief. The first thing you need to know is that you didn't do anything to cause this to happen, and there is nothing that could have prevented it from happening. It is okay to grieve (or to feel whatever else you may feel).

If your baby has been diagnosed with triploidy via amniocentesis (which is usually performed between week 15 and week 20 of pregnancy), you will probably be asked whether you wish to continue the pregnancy. This is an individual choice and you have to do what works for you. Some women prefer to terminate pregnancies that have fatal diagnoses, whereas others choose to continue the pregnancies, even though they are aware of the expected outcome. (Note that if your pregnancy is affected by a partial hydatidiform mole, there is no chance of the baby making it to term and being born alive. Your doctor will recommend termination to prevent possibly serious complications that could affect your health.)

If the triploidy diagnosis comes after your baby has already been born, it's a good idea to speak with a genetic counselor about what you should expect, in terms of caring for your baby. Most of the time, the recommended treatment is to provide comfort care rather than to pursue any intensive interventions. There are numerous support groups for parents of babies with serious chromosomal disorders, and you may find these to be comforting as you cope with this news.

Sources:

Brancati F, Mingarelli R, Dallapiccola B. Recurrent triploidy of maternal origin. Eur J Hum Genet 2003;11:972-974.

Triploidy. Texas State Health Dept. Birth Defects Risk Factor Series. Accessed: Mar. 3, 2009. http://www.dshs.state.tx.us/birthdefects/risk/risk24-triploidy.shtm

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