The Wall Street Journal recently reported that there is a fast-growing new market of women seeking to have their hymens restored so that they will appear to be virgins again. We need to review a number of points in Jewish law to understand the halachic perspective on this procedure.
The halachic status of betulah (virgin) has implications for the monetary amount written into the marriage contract. (In addition, only a betulah can marry the kohen gadol (High Priest); however, this law does not apply to ordinary kohanim and will become relevant only when the Beit HaMikdash, the Temple in Jerusalem, is rebuilt.)
The status of betulah implies that a woman has never had intercourse; it is not a comment on her hymenal tissues. A woman born without a hymen, or whose hymen has been stretched by the natural processes of maturity (or by tampon use), is still a betulah. On the other hand, a woman who has had either vaginal or anal intercourse but still has hymenal tissue in place, is not. (For further discussion see: Rav Yoezer Ariel. Taanat Betulim Bizman Hazeh. Assia 15 Kislev 5766.) Thus, a woman who undergoes this procedure will not regain her halachic status as a betulah. Whether she would, nevertheless, need to observe a period of niddah for potential dam betulim would appear to depend on opinions among the Rishonim (medieval halachic authorities) as to the purpose of this practice.
If the purpose of the surgery is for a woman who has had relations to try to prove that she has not, then it would be a clear violation of geneivat da'at, the halachic imperative not to mislead people (Shulchan Aruch Choshen Mishpat 228). As such it cannot be condoned. When the future husband is aware that his non-previously-married wife has in fact had intercourse in the past, there are ways to permit writing the word betulah in the ketubah (marriage contract) to avoid embarassment.
Undergoing surgery of any sort involves a risk to one's health. Unnecessary risk taking is not permitted under Jewish Law. Furthermore, self mutilation is prohibited (Mishneh Torah, Hilchot Chovel u Mazik 5:1). Therefore, cosmetic surgery of any sort is permitted only when required to alleviate significant physical or emotional difficulties (see for example Rabbi J David Bleich. Judaism and Healing. Ktav Publishing House 1981). It does not seem that the reasons normally presented for this procedure would meet that criterion.
On a purely theoretical level, it would also seem that a return to virginity is not to be strived for. Breaking of the hymen within the framework of marriage is viewed as a completion of the woman and the contract between the husband and wife, not a detraction (see for example, Encyclopedia Talmudit sv Be'ilat Mitzvah).