Usually, around 27 weeks or so, you will have a blood test to determine babies
blood type. Should baby have Positive
blood, you will get a shot
of Rhogam (Sp?) to help fight antibodies that would harm baby. I have never heard of miscarriage because of blood type.... I hope this helps. I have B- blood type, and my daughter has type +, so I had to get a shot during the 27th week.