Miscarriage and Stillbirth Risk in Down Syndrome

Understand Your Increased Risk of Pregnancy Loss

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You've probably heard of Down syndrome, but you may not know that there's an increased miscarriage and stillbirth risk in this disorder. Keep reading to learn more about the risks.

What Is Down Syndrome? 

Down syndrome is a chromosome abnormality that causes intellectual and physical problems in babies who are born with it.

Down syndrome is the most common genetic condition. It occurs in 1 in every 691 babies in the U.S.

It's usually caused by random genetic errors. That means it's not typically inherited from a parent's genetic makeup. We normally have 46 chromosomes. When there is an extra copy of chromosome 21, this is called trisomy 21. Trisomy 21 causes most cases of Down syndrome.

If you are over 35 years old, your odds of having a baby with a chromosome disorder such as Down syndrome are increased, but the odds of having a baby without a chromosome disorder are higher.

What's the Risk of Miscarriage? 

About 6,000 babies are born in the U.S. with Down syndrome every year. However, Down syndrome can cause miscarriage and stillbirth.

It's estimated that, on average, about a quarter of Down syndrome pregnancies that are not terminated result in miscarriage or stillbirth.

The pregnancy loss rates differ based on the mother's age and on how early Down syndrome is detected. (Timing of detection tends to depend on whether chorionic villus sampling (CVS) or amniocentesis were used).

A British study of Down syndrome pregnancies published in 2006 found:

  • The average fetal loss rate between the time of CVS and term was 32 percent, increasing from 23 percent for women aged 25 to 44 percent for women aged 45.
  • The average fetal loss rate between the time of amniocentesis and term was 25 percent, increasing from 19 percent to 33 percent across the same age range.

    ​Aside from maternal age, researchers do not know why some Down syndrome pregnancies are miscarried or stillborn, while others continue on to live birth. Genetic factors may lead to the condition being incompatible with life in some cases but not others.

    If you have learned that your pregnancy is affected by Down syndrome, you do face an increased risk of pregnancy loss. Or, your baby may make it to term, albeit with the expected special needs. You may be referred to a high-risk pregnancy specialist for increased monitoring for the duration of your pregnancy.

    After a Miscarriage

    If you had a miscarriage and chromosome testing indicated Down syndrome as the cause, you should know that the pregnancy loss was not your fault.

    Most chromosome disorders, including Down syndrome, are believed to be the result of random problems in cell division. In the small number of inherited cases, there's still nothing you could have done differently to prevent what happened.

    According to the March of Dimes, if you have one pregnancy affected by Down syndrome, your risk of another Down syndrome pregnancy is 1 in 100 until you turn 40 years old.

    At that point, your risk is based on your age. 

    Sources:

    Savva, G.M., Morris, J.K., Mutton, D.E., et al. (2006). Maternal age-specific fetal loss rates in Down syndrome pregnancies. Prenatal Diagnosis.

    Down syndrome. March of Dimes. July 2009.

    Morris, J.K., Wald, N.J., Watt, H.C. Fetal loss in Down syndrome pregnancies. Prenatal Diagnosis 1999. 19(2): 142-145.

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