An rh negative mother refused rhogam during her first two pregnancies. now she is pregnant with my son's baby. my son is b+. she waited for 6 months to see a doctor in her last pregnancy. should she visit a doctor?

Unfortunate: This was extremely unfortunate, and she may have been deceived by an anti-transfusion cult and/or anti-medical disinformation. Unfortunately, even the father has no rights with regards to the well-being of the unborn child. Most of the time, these babies come to term with no problem. These people may come around when they discover they've been deceived, but it's a hard road. Be strong.

You got lucky: If the mother has been sensitized against rh (called the rhesus antigen), then she will make antibodies that will cross the placenta into the fetus. When that happens, the result can be very serious disease or even fetal death. Before rhogam, death from this cause was very common.

Unclear question: It is not clear what you are asking. You should see your doctor and a blood test can be done to test if you are sensitized to rh and have antibodies to this blood group antigen.