If a couple has sex the night of their wedding do they need separate immediately following intercourse? It feels like a punishment for couples who actually wait, not even being able to enjoy the a full night together and then separating for at least 12 days.
If the woman is a virgin and her hymen is not perforated then after the first act of vaginal intercourse, she and her husband have to separate. This is the principle of דם בתולים, that the first hymeneal bleeding, in the Talmudic and Geonic period, was treated as menstrual bleeding. This practice even grew to include cases when no actual blood was seen on the assumption that some hymeneal blood must have been present.
This law would not apply if the woman has had vaginal intercourse in the past or has had her hymen surgically removed. Nowadays, many women will, by the time of their marriage, already have a perforated hymen due to natural (non-sex-related) activities over the course of her teens and twenties. If her gynecologist inspects her hymen and tells her that it is perforated in a manner similar to how it would look after the first act of vaginal intercourse, or that in his/her estimation there would be no bleeding as a result of intercourse, then a number of contemporary poskim rule that if no blood is seen, she would not be considered a niddah after the first act of sex. If, however, there was bleeding, then this would be דם בתולים and she would be a niddah.
As to physically separating and sleeping in separate beds. Yes – this is very challenging, not only because it means that they cannot continue to be sexual, but also because they just can’t hold and embrace one another at a time when they feel emotionally that they need to be doing so.
In terms of the Halakha, the Gemara says that after the first act of sex, the man must פורש, he must separate from his wife. The simple sense of this is that they cannot continue to have sex. Nevertheless, almost all of the Rishonim state that because Halakha considers this to be like niddah bleeding, the laws of הרחקות, distancing, applies, and husband and wife must sleep in separate beds, just as they do when the woman is actually in niddah.
It should be noted, however, that רשב”ם (הובא באור זרוע), מחזור ויטרי, ספר האורה, and others from Rashi’s school say that they can continue to share a bed if they are not naked and do not engage in sexual touch. The phrase used is לא להרחיק ממנה כאשה נדה, אלא פורש מתשמיש, הוא בכסותו והיא בכסותה… ומשום כבוד חתנות לא רצו להחמיר ולהרחיקו יותר, “he does not have to distance himself as if she were a niddah, he rather refrains from sex, and they can remain together, he in his clothes (i.e., not naked) and she in hers (so that they will remember not to have sex)… And for respect of the wedding they did not want to be more strict and demand greater distancing.” It seems that these Rishonim are of the opinion that total separation is asking too much at this stage. While this position is very marginal (it is not quoted in later poskim, and it is mostly unknown), there are those who choose to rely on it at least for the first night, and to sleep together and hold one another, without continued sexual activity, for the first night after intercourse.
Another way couples deal with this challenge is to not have vaginal intercourse on the first night. This allows them to be sexual together for a the first night, and the following day, and even another day or two, before they finally move on to intercourse after which she will considered to be in niddah. Not only does this give them a lot of time together physically and make the separating afterwards easier, it also allows them to expand their sexual repertoire and learn how to please one another and how to be sexual without it all being about intercourse.
There is evidence that this practice has been going on for centuries. It is a practice that a number of poskim roundly condemn because it leads, according to their pesak, to zera levatalah, wasting of seed, since the husband ejaculates outside his wife’s vagina. It should be noted, however, that other poskim are of the position that a man ejaculating outside his wife’s vagina, if it results from sexual activity between the husband and wife, is not considered zera levatalah, as it is part of marital sex. According to this position, it would be no different than sex during pregnancy or post menopause or when the women is using birth control is not zera levatalah. As you can imagine, this is a matter that is heavily debated.
Finally, I should note that the idea that sex on the wedding night is a mitzvah does not mean that sex must take place on the first night. As Rav Moshe and many poskim explain, it just means that since it is assumed that the wife wants to have sex that night, this becomes the mitzvah of onah – the husband’s obligation to satisfy his wife when she wants sex. If she does not want to have intercourse that night, then the ביאת מצוה will take place on a later night, when she wants it and is ready for it.