Can women have sex during their period?

Patient's question:

Can you have sex when your period comes? Is there anything bad about it? The help I want: Come quickly and help me answer

Doctor's answer:

During menstruation, sexual intercourse is not recommended for three reasons:
1. The cervix is open during menstruation. If sexual intercourse occurs during this time, it may lead to increased menstrual flow and prolonged periods.
2. It can cause kidney deficiency and lower back pain during rainy days, as stated in The Secret Records of the Stone Chamber: "When the kidney water (including) is deficient, the uterus becomes dry and barren, just like crops without rain and dew, leading to withering and deficiency."
3. Traditional Chinese Medicine also believes that sexual intercourse during menstruation can cause sperm to enter the bloodstream, which may result in infertility. The author, from the southern region, believes that the three points emphasized by Traditional Chinese Medicine are sufficient to answer the question, "Is it okay to have sexual intercourse during menstruation?"