The levonorgestrel-only method of pre-implantation/emergency 'contraception'

Whilst the Yuzpe method was the primary method of post-coital birth control from its inception in the 1970s, during the late 1990s researchers began investigations with the exclusive use of levonorgestrel, a progestin. This approach to pre-implantation birth control involves the ingestion of 0.75mg of levonorgestrel within 72 hours of unprotected intercourse, and an equivalent dose 12 hours later. (1) Newer studies have confirmed that the efficacy of levonorgestrel is unaltered by taking both tablets at the same time.

Compared to the Yuzpe method, the major 'advantages' of this newer method are a reduced incidence of side effects, notably nausea, vomiting and breast tenderness, and a higher pregnancy abortion rate.

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(1) Randomsed controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception Task Force on Postovulatory Methods of Fertility Regulation. Lancet 1998; 352:428-433 (Dr Helena von Hertzen and Dr Paul F A Van Look).