Lev 20:18 婦人有月經、若與他同房、露了他的下體、就是露了婦人的血源、婦人也露了自己的血源、二人必從民中剪除。
當佢死嘅之後，就以現代醫學指引來處理此問題： Is it Safe To Have Sex During Your Period?
Many men and women worry that having sexual intercourse during a woman's period is unhealthy. Though frowned upon in many cultures and faiths, sexual intercourse during menstruation is entirely normal and completely healthy.
Worries about this act generally stem from societal misconceptions about menstrual blood: most girls are taught from a young age that their menstrual blood is unclean and "dirty," and therefore should be hidden and contained at all times. However, menstrual blood is an entirely natural bodily fluid, and does not in anyway affect a man's penis or a woman's reproductive tract. As long as you are engaging in safe and protected sexual intercourse, it is entirely alright for you and your partner to have sex during your period. http://www.epigee.org/menstruation/sex.html
If a women is a carrier of an STD then her menstrual blood, like semen and vaginal secretions, will contain the STD whether it is the HIV virus or any other bacteria associated with a number of other STDS, including syphilis and chlamydia. Additionally, many women experience herpes outbreaks during their monthly periods, which may actually increase your risk of spreading this disease to your sexual partner. When engaging in sex, no matter what time of the month it is, it is necessary to wear a condom in order to prevent STD transmission.