Using condom during sex has been recommended to one and all in order to prevent STDs and pregnancy, but experts say that it is OK to do it without protection under these conditions:
1. Got checked for STDs and HIV
Get checked for STDs if you are sexually active in order to prevent the diseases from spreading and infecting others. The report of the tests for STDs is valid on till three months from the last sexual encounter you have, hence it is recommended to get yourself and your partner checked once you exceed the time period.
2. When she is ovulating
Women ovulate in between her menstrual cycle, this is the time when having unprotected sex will not impregnate her. So if it is the couple's mutual decision to have some fun without a condom during this period, they can definitely give it a shot. But it is advised to be well assured that your partner or you have not contracted any STDs.
3. If you are in a serious relationship
Do it ONLY IF you trust your partner completely and you are in a serious monogamous relationship. This would avoid the chances of being infected by any sexually transmitted diseases. Even if you get preggers, you wouldn't really have to fret much if your partner is good, loyal and supportive.
4. If you take other precautions to avoid pregnancy
You can escape from using condoms if you follow other precautions to prevent pregnancy, like having contraceptives or getting injections to avoid pregnancy. Make sure that you and your partner being sexually healthy and disease-free before you plan to do it this way.
Make sure the checking is done before you have all the fun and it happens with the consent of both the partners.