on Blood types, I think that's only relevant though if you are Rhesus negative (so O-, A-, B- or AB-) and your baby is positive.
Imagine that on the outside of positive blood cells are little + signs sticking off the outside. Someone with these sticking out is never going to make antibodies which attack + signs because they'd be attacking themself all the time.
In a rhesus negative person, you have nice smooth outsides to your blood cells. So, if you have a baby who is positive, their blood cells are covered in + signs. If baby's blood gets into yours at birth, your smooth blood will develop antibodies which will attack the +blood cells because they are foreign. Then, when you have another baby, if they are +, negative mum's body will have lots of antibodies hanging about waiting to kill the + signs on your baby's blood. Which is VERY bad for second babies, because they are attacked by their mummies.
Which is why rhesus negative mummies get anti-D at (or after?) giving birth, which stops the antibodies which attack + signs in subsequent babies.
I don't think it happens with other blood groupings (the A/B bit), so if you're positive, don't worry about it. If you are negative then your MW will tell you about the jab.
I'm so sorry if that didn't make sense, it's been a long time since uni!!
ON kicks, baby has been wriggling and squiggling loads today! I know i won't feel the same in a few months when they are proper punches in the bladder, but at the moment it's lovely!! I had 3 teenage girls round for a bible study and they asked what it felt like. I said "have you seen alien?..."