There is always a possibility for DS with any baby, any couple. Yours is just a slight higher chance. And yes even with different blood types you can get pregnant. Also as far as the blood types, it's called the RH factor. Google it. I had it. It is when one parent is pos blood type and the other is a neg. Like o+ and AB-. That is considered RH factor. If that is your case you can be treated with Rogham. Here is a web site that can give you all the info you need for the RH Factor. (
http://pregnancy.about.com/cs/rhfactor/a/aa050601a.htm) Wheither you have it or not is up to your physician and your blood types. Good luck and may God bless.