I’ve had this recently. No antibodies at booking in (third pregnancy) but after 3 shots of anti D (minor episodes of spotting due to an ectropion on cervix) slightly raised levels of antibodies were detected. They think it might be as a result of the anti D itself but are monitoring- blood tests every two weeks.
They don’t seem THAT worried so I’m trying to stay quite calm about it.
Am 29+6 btw.