I feel a little uncomfortable about having sex with my pregnant wife. When is it not considered safe anymore?
This is a good question, and the answer, as often is true with good questions is: it depends. In a healthy uncomplicated pregnancy, you can have intercourse as long as you want to—until your water breaks, essentially.
Couples vary tremendously in whether and when they want to have sex during pregnancy. Some couples feel extra close, and enjoy not having to worry about birth control or "trying" to conceive. Others worry (unnecessarily) about the baby, or feel that the baby is an observer, which can feel pretty weird. Some moms-to-be lose their sex drive during pregnancy, and prefer feeling intimate in other ways, like massage or cuddling. Nausea often pretty well kills libido. Body image can also be a plus or a minus for your sexuality during pregnancy. While some women feel sexy and curvy, others feel fat and unattractive, and need reassurance from their partners that they are still desirable. And some dads are just uncomfortable with having sex with a pregnant woman. Many of these negatives can affect the closeness of the couple, and require tenderness and good communication to negotiate your way through.
Medically, there are a few conditions that make intercourse risky. Your doctor or midwife may advise you to avoid intercourse if you have had vaginal bleeding or other pregnancy complications. Be sure to ask exactly what is prohibited—sometimes intercourse is a no-no, but orgasm is OK.
I hope this answers your questions. Don't be afraid to talk to your doctor or midwife about sexual concerns. She or he will be able to give you answers and advice tailored to your pregnancy.