1. Health

Triploidy

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Updated July 14, 2014

Genetic and chromosome disorders can have varying and potentially far-reaching impact on a baby's health. The effects of a chromosome can be anything from mild health concerns to being "incompatible with life," meaning an invariably fatal prognosis.

Triploidy is a disorder that falls on the latter end of the spectrum. The majority of babies with 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 supposed to have 46 chromosomes (23 pairs) with half of each pair coming from each parent. Triploidy means that a baby has three copies of each chromosome in each cell rather 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 causing 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 with 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.

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 only be diagnosed through 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 triploid. 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, the majority (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 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 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 ranging from numbness to confusion to grief. The first thing you need to know is that you didn't do anything to cause this to happen, and there is not anything 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, 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 a fatal diagnosis, 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 to 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 on 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 pursue any intensive interventions. There are numerous support groups for parents of babies with serious chromosome 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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