Anti-M antibodies are relatively common and naturally occurring. When anti-M antibodies cross the placenta, they may cause hemolytic disease of the fetus and newborn (HDFN). Anti-M antibodies account for less than 15 cases of HDFN reported in the published English literature. HDFN can lead to foetal anaemia, hydrops fetalis, hypoxia, heart failure, and even death.
To review the general guidelines and propose a less intensive management approach of anti-M antibody during pregnancy through the context of a case report.
We report a 25-year-old healthy pregnant G3P1011 woman presenting for antepartum care. At the time of delivery for the patient’s second pregnancy, she was found to have a positive anti-M blood screen, though she birthed a healthy-term infant. For her current pregnancy, the initial and repeat testings for anti-M were positive.
Since multiple samples from this patient were of low levels extensive maternal and foetal monitoring were deemed unnecessary in reflection of further reading and research. The patient had a spontaneous vaginal delivery of her third pregnancy at 38 weeks without complications.
Anti-RBC antibodies, including anti-M, are frequently identified in blood type and screening for pregnant patients. Guidelines call for intensive surveillance during pregnancy; however, knowledge of the specific antibody can help to provide more nuanced and less intensive care. As primary care physicians, being familiar with the guideline and the ability to counsel patients on anticipated care during pregnancy can help with family planning, compliance with testing, and patient anxiety and decrease intensive use of services that may not affect outcomes.

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