Open communication can defuse a lot of tension and allow you to relax, enjoy each other, and find ways to be intimate, whether or not you're having sex. Keeping the lines of communication open will help you support each other as best you can while you go through these changes together. Staying active. Having sex burns calories, which could help you and your partner stay active and keep fit. At this point, you may be too big, achy, or exhausted to even think about having sex. There's some evidence suggesting that a person may be able to transmit HIV, as well as STIs such as herpes, gonorrhea, and HPV, through microabrasions or tiny cuts in the mouth. And during the third trimester, if your partner has ever had oral herpes, you should not receive oral sex at all, whether or not your partner has symptoms. Sex during the third trimester is safe if you're having a healthy, normal pregnancy.