Dear Mamma3, I did misanderstand, sorry for that. Thank you a lot for the information you shared here.
This is actually possible if it comes to an even minor mixing of fetal blood with the mother's blood, in the sinuses of the placenta. But, that normally does not happen. So may be the homeopathic answer here would be at getting less fraigile blood vessels in the placenta. Could Arnica be of value here?