Why is the first pregnancy is USUALLY not a problem but each subsequent pregnancy is – remember antibody types produced. If this is the patient’s first known pregnancy, how could

Why is the first pregnancy is USUALLY not a problem but each subsequent pregnancy is – remember antibody types produced.  If this is the patient’s first known pregnancy, how could this baby still be at potential risk should mom have the blood type that is of concern in the first place? Also describe how the fetus is affected – which system(s) are in greatest danger. Lastly, what is Rhogam and how does it work? If Rhogam fails, what other treatments may be tried?