Heavy work does not increase the chances of miscarriage provided that the mother is conditioned to the work. If you had ever been pregnant or had a clue about female anatomy or reproductive biology/medicine you'd know that. Your doctor's make a point to tell you to maintain your activity levels, whatever they are, pre-gestation.

You're repeating debunked medical beliefs from the 18th century, from back when they also thought leeches were therapeutic and didn't know washing their hands was a good idea.

Please feel free to keep your antiquated 'expertise' to yourself. Its not really adding anything of value here.