The first is that an infection could result from foreign substances introduced into the vagina. So you should avoid vaginal sex after anal sex, and you should probably avoid introducing massage oils or flavored lubricating gels into the vagina as well. As with other activities during pregnancy, let common sense be your guide. The second risk is that labor might be induced either by the uterine contractions of orgasm or by certain chemicals in semen called prostaglandins. Women with no complications during pregnancy should not be concerned that intercourse will induce labor.
Many pregnant women feel an increased desire for sex, usually during the second trimester.
Early-pregnancy nausea and fatigue have worn off, and an increased blood flow to the pelvis and breasts can make arousal and orgasms easier. Certain pregnancy hormones may heat up the libido, too. On the other hand, it's normal for sex to be the last thing on your mind. However you feel, you needn't worry that intercourse will hurt the baby. If you're not sure, ask.