It's possible that blood groupings were mentioned when Sheila charred for Ann, or just woman to woman talk about hospital stays whilst pregnant. Sheila did visit Oak Farm with Daniel and Nicholas. She asked Ann on that occasion to take a photograph of her to show to Christine. I don't say Ann knew definitively and I don't believe it myself, though the Bamberettes will claim anything which suits their case, as the guilters know from old.
Why would Sheila have any understanding or knowledge of her enzyme and protein groups as a result of her pregnancy? And even if she did who exactly would be able to recall and relay such information?
PGM = Phosphoglucomutase (enzyme)
EAP = Erthrocyte Acid Phosphatase (Enzyme)
AK = Adenylate Kinase (Enzyme)
HP = Haptoglobin (Protein)
Does anyone here know their groups?