This coming from the reliable source of a nurse midwife, for the most part, in real life, the hot tub is out only during the first trimester, and after that, it's okay, just on a low setting. As for the treadmill, if a mother to be is already very active and athletic, then they can use the treadmill more, though just using it to walk would be better.
But I'm off topic so.....I still hate that the last few bachelor parties I have had, no one but the dancers showed.