There are many factors to take into consideration about sex during pregnancy and there are many opinions about it. The only thing you can be sure of is that your sex life will undergo changes during your wife's pregnancy. The most noticeable change is the frequency of sex. Many couples fear compromising their unborn baby's safety; this isn't too much of a factor since the baby is safely enclosed in an amniotic sac. This will protect the baby from everything except really rough sex.
There are big changes in the levels of sexual desire that both partners feel during pregnancy. Many men fear that they are sterile before a successful conception. Once the pregnancy is confirmed, a dad-to-be can feel a lot more “masculine”. They will also feel emotionally and physically closer to their wives than before. For the mom-to-be, not having to worry about contraception may do away with inhibitions. She may feel more attractive, due to her curvier figure, and more connected with her partner. All of this translates to increased sexual activity, particularly during the first trimester.
While some men experience heightened desire during their partner's pregnancy, others do not find the physical changes to be attractive. The changes in their partner's body represent functionality rather than fun. The fact that the baby will take physical priority in a few months can also add to the man's sexual discomfort.
From the woman's perspective, being pregnant means dealing with nausea from morning sickness (which isn't limited to mornings), leaking breasts and mood swings due to hormonal changes. She may feel sexually aroused, but have fears that she might hurt the baby during sex, or that her partner is not attracted to her any more. Some women just feel fat, which will be a turn-off for them.
Due to the confusion and mixed feelings that both partners feel about pregnancy, open discussion between couples is the best course of action. Find a common ground that satisfies sexual needs and does not make either partner uncomfortable. Try out different sexual positions; you may even want to limit intercourse or do away with it altogether, particularly in the last weeks of pregnancy. There are many different ways of pleasuring each other that doesn't involve intercourse. Have fun experimenting and rediscovering manual sex.