My Daughter Has Been Told That The Prevalence Of Anti-M

My daughter has been told that the prevalence of anti-M iso immunisation may be increasing. SHould my son be tested for Anti-m. Also the fetal heart beat is 86bpm which is low She is 5 weeks 6days +/- 4 days. she is having another ultra sound in 2 weeks and has been told that there is a good chance she could lose the baby