The blood type concern only happens when the mother is negative (this refers to the RH factor; it’s the + or – after the letter) and the father is positive. You’re both positive, so even if the baby ends up negative (it’s possible), there won’t be an issue with blood types.

If one parent is positive, the baby may or may not be positive. It’s possible that some of his/her blood might mix with your fiancee’s (it’s actually a rare situation, often caused by trauma, but it could even be a light trauma like tripping and falling that causes it to happen). This causes her immune system to react if the baby is positive, but the mother is negative. She’s positive, so you don’t have to worry. There are shots to prevent a reaction, and it usually isn’t a big deal on the first child–it’s the second positive child that causes problems.