UPA and LNG in emergency contraception: the information by EMA and the scientific evidences indicate a prevalent anti-implantation effect Article published in "The European Journal of Contraception and Reproductive Health Care"
Rationale and objectives: Emergency contraceptives pills (ECPs) are described as drugs that work by either inhibiting or delaying ovulation without affecting implantation. In our opinion, as we aim at demonstrating, both EMA documents and the experimental papers indicate that they prevalently inhibit embryo-implantation.
LNG-ECPs: literature: LNG-ECPs never prevent ovulation when are taken in the most fertile days (EMA-EPAR on ellaOne© p. 9, first table). Conversely, they prevent the formation of an adequate corpus luteum. When they are taken pre-ovulatory ovulations occur regularly, but pregnancies do not appear. Taken after ovulation, they seem ineffective in preventing pregnancies.
UPA-ECPs: literature: EllaOne© prevents ovulation only when is taken in the first fertile day. Thereafter, its anti-ovulatory effect drops sharply and becomes insignificant (8%) 36 h before ovulation, in the most fertile days (Brache); its decreasing anti-ovulatory effect cannot explain a consistently high effectiveness in preventing pregnancies (>=80%) that does not decrease depending on which of the 5 d it is taken after unprotected intercourse. Besides, ovulation occurs regularly in 91.7% of women taking ellaOne© weekly, for eight consecutive weeks (EMA-CHMP-Assessment Report ‘EMA/73099/2015’: study HRA2914-554, p. 7). Lastly, Lira-Albarrán administered ellaOne© to women in the most fertile pre-ovulatory days: they had normal ovulation, but their endometrium, evaluated through samples obtained in the implantation window, became inhospitable: the expression of 1183 genes was exactly the opposite of that observed in the receptive pro-gestational endometrium. This agrees with information by EMA-CHMP-Assessment Report ‘EMEA/261787/2009’ (p. 8): after UPA administration ‘the proteins necessary to begin and maintain pregnancy are not synthesized’.
Conclusions: Emergency Contraceptives work prevalently by preventing embryo-implantation.
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