Abstract: Post coital contraception should not be considered as first line contraception. However, in cases where needed, it can halachically be used.
Discussion: There are two types of post coital (“emergency”) contraception – hormonal manipulation and insertion of an intrauterine device (IUD) There are now three types of hormonal manipulation available. . The first type on the market was a combination of estrogen and progesterone, known as the Yuzpe regimen. The second type is levonorgestrel, taken either at two doses of 75 mg 12 hours apart or 1.5 mg all at once.  The progestin only preparation has been found to be equally or more effective than the combination estrogen progesterone preparations and with significantly reduced side effects.Therefore, the current ACOG recommendation prefers progestin only preparations. . Progesterone can be used for up to 72 hours. In addition, progesterone receptor modulators have been shown to work as well even better than progestin  and can be used for up to 120 hours.
A copper intrauterine device (IUD) inserted within 120 hours post coitus is the most effective method . However, many orthodox women will not want to leave the device in place as an ongoing contraceptive. For these women, the discomfort and expense of the insertion procedure will not be counterbalanced by the advantages of long term use.
The halachic status of post coital contraception differs from that of the corresponding method of ongoing contraception for two reasons. First, emergency contraception is taken after intercourse for the specific purpose of preventing pregnancy. With routine contraceptive methods, pregnancy is already precluded prior to intercourse. The latter situation more closely resembles intercourse when a woman is infertile or already pregnant, which is permitted in Jewish law. Furthermore, although the methods of action are still a matter of debate, it appears that post coital contraception acts both by interfering with ovulation and by inhibiting implantation of the fertilized egg. This differs from hormonal contraceptives taken on a regular basis, which act only by inhibiting ovulation, and the IUD, which prevents fertilization. According to some halachic opinions, the action of emergency contraceptives is somewhat similar to abortion and thus problematic in Jewish law.
On the other hand, emergency contraception is less problematic than induced abortion as there is an underlying doubt that the woman is even pregnant at all. Furthermore, even if she is pregnant, the pregnancy is quite young. Abortions within 40 days of conception are easier to permit halachically than those later in pregnancy. Therefore, if a woman is using another permitted method that has failed, and the risk if she gets pregnant is substantial, there is room to permit post coital contraception. There is certainly room to permit emergency contraception if prescribed after a case of sexual assault.
It is common practice when administering emergency contraception, to do so as soon as possible after intercourse. Recent studies have shown that, although there is a linear correlation between efficacy and time from intercourse to treatment, results are still very good when administered up to 120 hours post coitus. These data are significant when the patient is uncomfortable with the proposed treatment and wishes to consult with a halachic authority at the expense of a few more hours.
Implications for care: Post coital contraception is more problematic in Jewish law than pre coital contraception. Therefore, it is best to assure that correct procedure is understood when prescribing contraception for women who need it for halachically approved indications.
When there is a true need for emergency contraception, it can be used, as it is less of a halachic problem than permitting induced abortion.
 Cheng L, Che Y, Gülmezoglu AM. Interventions for emergency contraception. Cochrane Database Syst Rev. 2012 Aug 15;8:CD001324.
 Shohel M et al. . A systematic review of effectiveness and safety of different regimens of levonorgestrel oral tablets for emergency contraception. BMC Womens Health. 2014;14:54..
 American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 112: Emergency contraception. Obstet Gynecol. 2010 May;115(5):1100-9.
 Richardson AR , Maltz FN. Ulipristal acetate: review of the efficacy and safety of a newly approved agent for emergency contraception. Clin Ther. 2012 Jan;34(1):24-36.