RH negitive

H

I went to my OB today for my 11 weeks checkup. I went in knowing they would try using the Doppler to find a heart beat but couldn't and had to do an ultrasound. They found it and said my uterus sits far back. The midwife also informed me that I'm RH negitive and did a poor job of explaining it. They gave me a shot and sent me to do labs. Can anyone give me some better info on being RH negitive and what it means for my Baby? Thanks.