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human
ELI5: Rh positive and negative and why it matters so much when it comes to having kids

Yeah yeah I'm an idiot lol. I'm sure it's all so simple but I'm pregnant and honestly, lacking quite a few brain cells thanks to it.

Can someone explain to me why Rh positive and negative matter when it comes to reproducing and even marriage?! I just read something that said Rh negative women should not be with Rh positive men and I don't understand any of it.
gpt
Your red blood cells might have a protein on them called Rhesus protein. It's hereditary. We call people with Rhesus protein "Rh positive," and people without it "Rh negative."

If mom is Rh negative and dad is Rh positive, the baby could be either. In the case of Rh negative mom and Rh positive baby, mom's immune system will treat the baby's blood like a foreign substance. So if any blood from the baby gets into mom's bloodstream via the placenta, her immune system will attack it by making antibodies.

If any of the antibodies from mom's immune system get back into the fetus's bloodstream, they will break down the red blood cells in the fetus's body. This can lead to the baby developing jaundice while in the womb. 

Now, all that being said, it's not really that big of a deal if you live somewhere with proper prenatal care. Your doctor should discuss Rh factor incompatibility with you, and if you are Rh negative, there's medicine you can take so that your baby doesn't wind up with jaundice.