Embryo in uterine implantation is a complex and rnultifactor-related process and is a downstream and ideal point for woman fertility control. Understanding the cellular and molecular mechanism of implantation is a prerequisite for development of anti-implantation contraceptives. In spite of considerable accumulation of information from the laboratory animals that has been achieved, it is difficult to generate such information in human due to ethical restriction and x-perimental limitation, and the present knowledge for understanding the definitive mechanisms which control these events remains elusive. Embryo implantation can also occur outside uterus. Some women with abdominal pregnancies could successfully complete the processes of gesta-tion nd bear normal babies, implying that implantation itself may be not an endo-metrium-specific process. Reproductive biologists should cooperate with gynecologists to further comparatively study the molecular and cellular mechanisms of implantation normally occurring in endometrium and abnormally appearing outside uterine cavity. Such collaborative studies may generate new important information for developing anti-implantation contraceptive and for tech-niques of accu- rate diagnosis of ectopic pregnancy. A specially designed GnRH-2 analog and a combination use of low dose RU486 and gossypol as anti-implantation contraceptives have been suggested.
