Theoretically, this is an absolutely safe period. However, sexologists show, based on animal studies and unfinished human studies, that fertilization can occur during the menstrual cycle. It is possible e.g.. then, when intercourse is accompanied by a very high level of sexual arousal. Interestingly, this also applies to negative feelings. For example. it is possible to conceive in a theoretically infertile period as a result of rape. Sexual intercourse during menstruation is not harmful to your health, but they carry a much greater risk of contamination with a variety of viruses and bacteria. For this reason, and for hygiene reasons, most sexologists advise against intercourse during menstruation.