I know, as a nurse, that pregnancy during sex usually does not harm either the woman or the baby. And many women experience an increased sexual appetite, especially during the second trimester.
The obvious caveats to it not doing harm are, of course, if there are any risks involved in the pregnancy, if the woman has had previous miscarriages or preterm labor, or has a low-lying placenta (all things to be checked with your doctor)
Sexual intercourse CAN induce contractions. I also recommend a night of "hot loving" for women who are overdue. But it can also induce contractions in a woman prone to preterm labor. Semen contains prostoglandins, the same hormone secreted by women to begin labor (and for nursing) (that's why sex makes your breasts leak if you're breast-feeding, in case anyone was wondering)
I would also have to agree with Liza, that maybe activities with other men be limited to touching and oral. The actual sexual activity would most likely not be a problem, but sex with other partners DOES carry risks, even WITh protection, and why would you want to take that chance while pregnant?
I also know that pregnant women do turn some men on a LOT. At least, that was MY experience *blush* Be sure the men are gentle with you, and use positions that are comfortable for you. There are plenty of books and websites addressing sex during pregnancy that can offer advice on sexual positions. Myself, I found lying on my side, rear-entry to be the most comfortable. (I had VERY large babies)
Just be careful, and check with your own doctor to be sure sex is okay for you at all.
*and it IS only 9 months*
After that, sex will be the LAST thing on your mind for a while, anyway!
SLEEP will take on a MUCH greater importance!
Layla