I have IBS and even though I only make it to nearly 8 weeks, there was a huge improvement nearly right away. Most things pass right through me (sorry) but while pregnant it stopped, so the constipation thing worked quite well for me.

Can't imagine how bad it would be if you were normally constipated tho... And I don't have it very bad either, and the IBS support tablets usually fix it, when I bother to take them.