I would think that the mw is just being extra cautious. Your doc probably didn't worry about this as your m/c were all early. Personally, I think you should try not to stress to much (I know easier said then done) and just accept the extra monitoring as meaning you are going to be cared for extra well. I am sure that the midwife didn't mean to alarm you, she just wants to make sure you get the best of care so you and you bub have the happiest healthiest journey you can.