In a girl the opening of the vagina is partially covered by a membrane known as the hymen. In most cases there is a hole in this membrane which allows for the exit of menstrual blood and which is generally large enough to accommodate a thin tampon. With the insertion of the penis during first intercourse, this membrane is stretched to the sides and may tear slightly, leading to bleeding. This bleeding is known as dam betulim (blood of virginity). While this is clearly not uterine bleeding, the woman nevertheless has the status of niddah by rabbinic enactment.

If the bride was a virgin, the couple completes the first intercourse normally, even if dam betulim has already begun. After intercourse is completed, they separate and she observes all the laws of niddah.

If no blood was seen, and if intercourse was completed normally, she has the status of a niddah.

If blood was seen, even if intercourse was not completed normally, e.g. there was only partial penetration, she is a niddah.

If no blood was seen, and the couple either did not complete intercourse normally or are unsure whether they did, they should contact a rabbi to clarify how to proceed.

Unlike other women, according to all traditions a virgin bride must wait only four days before starting to count the seven blood-free days. Sometimes her regular menses will begin during this time, leading to a long interval before she can immerse in the mikveh. If her menses did begin before immersion, even a bride must wait the minimum five days, counting from the time of intercourse. During this entire time, the couple observes all the regulations that apply when the wife is a niddah.

If the bride is a virgin but knows or suspects that she has no hymen remaining, a specific halachic question should be asked.