RU486 combined with PG analogs in voluntary termination of pregnancy

Are animal models relevant to key aspects of human parturition?

Preterm birth remains the most serious complication of pregnancy and is associated with increased rates of infant death or permanent neurodevelopmental disability. Our understanding of the regulation of parturition remains inadequate. The scientific literature, largely derived from rodent animal models, suggests two major mechanisms regulating the timing of parturition: the withdrawal of the steroid hormone progesterone and a proinflammatory response by the immune system. However, available evidence strongly suggests that parturition in the human has significantly different regulators and mediators from those in most of the animal models. Our objectives are to critically review the data and concepts that have arisen from use of animal models for parturition and to rationalize the use of a new model. Many animal models have contributed to advances in our understanding of the regulation of parturition. However, we suggest that those animals dependent on progesterone withdrawal to initiate parturition clearly have a limitation to their translation to the human. In such models, a linear sequence of events (e.g., luteolysis, progesterone withdrawal, uterine activation, parturition) gives rise to the concept of a "trigger" mechanism. Conversely, we propose that human parturition may arise from the concomitant maturation of several systems in parallel. We have termed this novel concept "modular accumulation of physiological systems" (MAPS). We also emphasize the urgency to determine the precise role of the immune system in the process of parturition in situations other than intrauterine infection. Finally, we accentuate the need to develop a nonprimate animal model whose physiology is more relevant to human parturition. We suggest that the guinea pig displays several key physiological characteristics of gestation that more closely resemble human pregnancy than do currently favored animal models. We conclude that the application of novel concepts and new models are required to advance translational research in parturition.

RU 486/prostaglandin: considerations for appropriate use in low-resource settings

Antiprogestins represent a new class of promising drugs in fertility regulation, especially in early termination of pregnancy. RU 486 (mifepristone), manufactured by Roussel-Uclaf and marketed under the international trade name Mifegyne, is an antiprogestin tablet that is used sequentially with a prostaglandin for non-surgical termination of pregnancy. It has been chosen as a pregnancy termination method by over 100,000 women in France since its regulatory approval there in 1988. In addition, RU 486/prostaglandin was approved in July 1991 for use in the United Kingdom and an application for approval is being considered in Sweden. In Western Europe, it seems, RU 486/prostaglandin is increasingly accepted by medical experts, regulatory officials and women as an alternative to vacuum aspiration or dilation and curettage (D&C) for early pregnancy termination.

As the use of RU 486/prostaglandin becomes more established, health practitioners and women's health advocates are beginning to consider the feasibility of using this method for pregnancy termination in low-resource settings.