Chance of having another baby with trisomy 13

Hi, I am going to have a D&E tomorrow as my fetus of 15 months has trisomy 13. I had a CVS that detected that.
I am 44 years now and in Jan. 2009,  45.   I know that trisomy 13 occurs with age. What are my chances of having another baby with trisomy 13 if I try again? I cried a lot and depressed however I have to move on as I have a 4 years healthy girl I conceived at 40? Is true that trisomy 13 occurs due to translocation? Should I go see a genetic specialist to find out if my husband and I suffer of translocation?

Appreciate your response,
Sincerely

[Lisa Kessler, MS, CGC]

I am so sorry for your loss.  It sounds like an extremely difficult situation for you and your family.  

As you know, trisomy 13, also called Patau Syndrome, occurs in about 1 in 5,000-10,000 live born infants.  Trisomy 13 is generally caused by an extra copy of chromosome #13 (three copies of chromosome #13).  Typically, we have 2 copies of each of our chromosomes.

It is very unusual for a family to have a second child with Trisomy 13.  This can occur when a baby has Trisomy 13 due not to a complete extra copy of chromosome 13, but rather due to a rearrangement of piece of chromosome 13 with another chromosome. This is called a translocation which can sometimes run in families.  If you had a karyotype from this pregnancy from your CVS, then this test result would be able to determine if a translocation was present.    

If there is no translocation present, your actual risk for another pregnancy to be affected with a chromosome abnormality is dependent on how old you will be when you deliver. For example, if you will be 45, it is estimated at about 1 in 20.
  
It may help to meet with a genetic counselor to discuss the chances that a future pregnancy may have a chromosome problem.  You can find a genetic counselor through the NSGC (National Society of Genetic Counselors) website.   Best to you and your family.