My experience is this....I have been pregnant now 7 times. 1 daughter and 5 losses and now pregnant with twins (which was not done by IVF). In ALL my other pregnancies, I experience NO MS whatsoever. With my daughter, I puked ONE time and that was after getting overheated in the shower. But no daily MS at all.
With the twins, at 5wks and 3dys I started feeling a BIT naseaus. However, I am nearly 10 wks now and have yet to puke. I have dry heaved 3 or 4 times (both time after a hot shower) and gagged a few times on bad smells (my vitamins or somehting else that set me off), but NO puking.
So, I can definately say that the Twins have exxagerated my MS from what I have experienced in other pregnancies. BUT...I will say that if you have nothing to compare it to (other pregnancies) than it will be hard to say what you will get, because not everyone gets MS and others, even with a singleton get it worse than even I have it now....so you never know. AND some get it as early as conception, while others don't get it until 7-9wks!! Just be prepared for anything.