Statistics

The most common trisomy is Trisomy 21, also known as Down Syndrome and the 18 is the second most common trisomy. It occurs in about 1 in 2500 pregnancies, resulting in 1 in 6000 live births. Stillbirths that occur in the 2nd and 3rd trimester are factored in that statistic. Most babies die before birth or those who do survive during birth live for less than a year.However, a small number of babies (10% or less) live more than 1 year, with some surviving into their teens and beyond.

Prenatal Genetic Testing and Birth Defects: Comparison between Trisomy 13 and 18 

The number of babies born with trisomies 13 and 18 were affected by prenatal diagnosis and the option to end pregnancy in recent years.

l  Prenatal cytogenetic testing was reported among 71% of trisomy 13 case infants and 76% of trisomy 18 case infants.

l  Among mothers of case infants with prenatal cytogenetic tests, 61% of those with infants with trisomy 13 and 60% of those with infants with trisomy 18 had elective terminations.

l  The mother’s age was a risk factor for both conditions: 46.9% of the trisomy 13 case mothers and 67.1% of the trisomy 18 case mothers were 35 years of age or older.

l  Among liveborn infants with trisomy 18, 60.4% were female and 39.6% were male.