Trends in blastocyst research with relevance to development of contraceptives: General discussion.

ABSTRACT

The Indo-US symposium on Blastocyst Research concluded with a round table discussion on trends in research with particular relevance to the development of contraceptives. A number of events crucial to the initiation and maintenance of implantation were identified and possibilities of developing a contraceptive modality based on interference with these events in implantation were discussed. There is a great demand from women and national family planning programmes for simple, effective and safe methods of fertility regulation which can be self-administered either post-coitally or for use when menses are delayed by a few days. The availability of such contraceptive technology would limit exposure to fertility regulating agents only to such occasions when coitus takes place or when there is a probability of pregnancy. Moreover, if fertilization had indeed occurred, interruption would take place at the earliest stage of pregnancy thereby reducing the excessive bleeding encountered with later termination of pregnancy. Methods of post-coital contraception used so far have been reserved primarily for emergency situations to protect women from unwanted pregnancy resulting from rape or acts of unprotected coitus or failed barrier methods. Probabilities that an act of coitus will lead to conception, with reference to the estimated time of ovulation, is highest during the fertile period (9·6+ 2·6 days). The objective of any form of contraception related to coitus would be to interfere with implantation irrespective of the day when the drug is taken. A drug effective in inhibiting implantation during the most fertile period is likely to be effective in other periods of the menstrual cycle also. The areas selected for discussion were Uterine sensitivity —What are the factors that regulate uterine sensitivity and maternal recognition of the blastocyst? —What are the factors involved in the development of uterine refractoriness? Can refractoriness be induced? —Are there specific uterine and blastocyst proteins involved in implantation? —Is induction of a short luteal phase a possible approach to modify uterine environment and render it hostile for implantation?