What are Chromosome Differences?

Inside each of the cells in our body, there are string-like structures called chromosomes which package all of our DNA. DNA contains genes that instruct our body how to grow, develop and function on a day to day basis. Some people have extra or missing chromosomes, which means that they have a chromosome difference. When the unborn baby has a chromosome difference there may be long term effects on health and learning. Sometimes having a chromosome difference can have severe effects and results in the loss of the pregnancy. 

How Often do Chromosome Differences Happen?

• Two chromosome differences that can happen are trisomy 21 (Down syndrome) or trisomy 18 (Edward syndrome).
• Any pregnant person has a chance to have a baby with trisomy 21 or trisomy 18. This chance increases with the age of the mother (or the age of egg donor). 
• Trisomy 21 and trisomy 18 usually happen by chance in the sperm or the egg that made the pregnancy, and do not generally run in families.

*Ages are at expected time of birth. 

Adapted from:

JK Morris and NJ Wald. J Med Screen 2007;14:5-7

Which Chromosome Differences does Prenatal Screening Test for?

Currently, multiple marker screening in Ontario (eFTS and MSS) will offer information about:

• trisomy 21 (Down syndrome)
• trisomy 18 

NIPT that is funded by the Ministry of Health (MOH) or paid for out of pocket will offer information about:

• trisomy 21 (Down syndrome)
• trisomy 18
• trisomy 13
• sex chromosome differences

Nominate a Condition

Have your voice heard! Did you know you can nominate a condition for addition to the prenatal screening program in Ontario?