The Rhogam Shot
The Rhogam shot is given to pregnant women in order to prevent Rh antibodies from developing in her immune system What are Rh antibodies and why are they bad? Well, here's the story.
There are negative and positive blood types. They refer to your body's RH factor. For example O- blood type is RH negative. For RH- mamas, if the baby's father has a positive blood type your baby could be too. If it is your body could see it as a foreign substance. Your body will develop antibodies to fight off this little invader as if it were any other germ/disease. If it's your first pregnancy, generally the baby will be fine because the body doesn't know the baby's blood type until their blood mixes with yours - like during delivery. However, if the baby is a positive blood type your body will develop the antibodies that could 'attack' any future pregnancies.
All women with a negative blood type will get the shot at some point in their pregnancy. The only way to get out of it is if you know FOR SURE the father is also a negative blood type. If you experience ANY slight bleeding/spotting early in your pregnancy you need to get the shot right away because your blood could be mixing with the baby's, which could trigger your body to develop the antibodies.
And now you know :)