If the couple wish to engage in sexual intercourse more than once then it is best that they take a bath before the second coitus. If not, then at least to perform wudhu. If not they should at least wash their genitals clean.
It is the experience of the elders that a person who re-engages in sexual intercourse without doing any of the above, the resultant off-spring will be mentally-retarded or will be niggardly in nature.
The author of IHYA emphasizes that the least every couple should do before re-engaging in sexual intercourse is to pass water and wash their genitals clean without this they should not indulge in sex. The result will be harmful and detrimental to them.