It is estimated that approximately 80% of Trisomy 21 pregnancies end in a miscarriage (pregnancy loss before 20 weeks of gestation) or intrauterine fetal demise (pregnancy loss after 20 weeks of gestation), while 20% may progress to term delivery.

When do trisomy babies miscarry?

Most pregnancies with a rare trisomy miscarry before 10- 12 weeks of gestation. A pregnancy that progresses beyond this gestation may have mosaicism, which means there is a mixture of normal cells and cells with the rare trisomy.

Do Down syndrome babies usually miscarry?

Down syndrome is one of the most common genetic problems that can occur in pregnancy. If a pregnancy has a genetic abnormality it will usually be miscarried early. However Down syndrome does not always miscarry.