RH incompatibility

[CharlieB93]

Probably a silly question but i've been googling and can't find the answers..

I'm RH negative, OH is RH positive, our unborn baby is RH postive, understandably we are at risk of RH disease.

My question is - my mother is RH positive yet gave birth to me as a RH negative baby. Why is this not an issue? We we're still different blood types when she was carrying me.
Also my mother and father are both RH positive - how come i'm RH negative (i've been assured i'm not adopted - and apparently if they accidently switched me they would have soon switched back haha)

Carrying a rh-ve baby if your Rh+ve doesn't cause problems.
Being Rh+ve means you've reacted to Rh. The Rh status of your baby doesn't affect anything.
You get 2 copies of the Rh gene, one from each parent. If both your parents are Rh+ and Rh- then they'll be Rh+ overall but can each by give you Rh- which will make you Rh-.
If you're Rh- and carry a baby who is Rh+ your body will think your baby's Rh+ is infection and make an immune response, this can cause problems (normally in future pregnancies). Someone who is Rh + knows it's not infection and so won't react.

Hi, Rhesus is a little different than the other parts of your blood group (A,B,O). Rhesus negative basically means you have no Rhesus.
The problem occurs when you (as a mother) have non and your baby has Rhesus as your body sees the Rhesus as a bad thing and develops a fight response to it (like an immune response to chicken pox for example)
Your body is then primed to attack any future Rhesus in your body (from a second child).
For your mother it wasn't a problem because she had Rhesus and you did not, there was nothing to fight. So in a way RH- isn't a DIFFERENT blood group it's just the absence of part of the blood that your mother does have.
Finally, like many things that are genetically inherited it's not just from one copy of a gene. Your parents will both be what they call heterozygous, meaning they have one copy of RH+ and one copy of RH- in their genes. This makes them physically RH+, but as you only inherited one copy of the gene from each parent you got two RH- copies, making you RH-. It's similar to the inheritance of brown versus blue eyes with brown being akin to RH+ and blue like RH- (This is a very very simplified account)
I hope that makes sense.

RH neg isn’t dominant so your parents will appear as RH positive if they have one of each. If you’re neg then must both have recessive RH neg. I.e mum is +- dad is +-

Sorry, x-post. Basically what PP said!

Thank you! That makes so much sense, so the immune response is because my immune system isn't used to RH so would attack like it was a foreign body. I was thinking of it such as if your mum and dad both have brown hair you'd have brown hair etc... I was just curious how it worked :D

I was in the same situation as this. If there’s any risk of an “exposure” to the babies blood during early pregnancy (usually indicated by bleeding) you will be given an anti-D injection to stop you producing antibodies against the rhesus antigen. Otherwise you tend to get it routinely during the third trimester to make sure it doesn’t happen.