INTRODUCTION

 Premature labor and delivery are associated with excessive perinatal morbidity and mortality and continue to be a major health problem. In the United States alone, approximately 8% of births occur prior to term. Although we have made great strides in the care of preterm infants, we have made very little progress in prevention/treatment of this disorder. In order to effectively accomplish this goal, it is imperative that we have a complete understanding to the processes involved in the initiation of normal term delivery. However, such knowledge is lacking. It is this lack of understanding that has prevented us from making adequate progress in dealing with the abnormal timing of delivery.

 With this in mind, I would like to discuss our findings in the area of fetal-maternal communication and how this may impact our current knowledge in the area of the initiation of labor. Due to obvious ethical considerations, human experimentation is extremely limited. We have therefore relied upon the rhesus monkey as a model. Although not identical to the human, the rhesus monkey bears a number of striking similarities to the human during pregnancy. These include similar placental anatomy, endocrinology and fetal physiology. In this model, catheters are surgically placed in both the mother and fetus as well as in the amniotic fluid cavity. The mother is placed in a vest and tether system which then allows simultaneous sampling from both mother and fetus as well as continuos uterine activity recording from conscious, unanesthetized animals during the latter portion of gestation.

 A key observation that served as a cornerstone for the majority of our studies centered on the measurement of uterine contractions. In chronically catheterized pregnant rhesus monkeys near term, we observed a well-defined pattern of contractility. As illustrated in Figure 1, uterine activity occurred most frequently during the hours of darkness, with peak activity observed between 1900 and 0100 hours. This has been a consistent observation from our group (Ducsay and Mc Nutt, 1989;Ducsay and Yellon, 1991, Matsumoto et al., 1991) as well as others (Haluska and Novy, 1993 ;Honnebier et al., 1991). This phenomenon is only apparent during pregnancy and persists in the latter part of gestation and as delivery approaches becomes even more obvious. These data suggest that there is a well-defined communication between other and fetus. In examining these data, two obvious questions arise. The first is what is the purpose of such an interesting phenomenon and second what drives or causes these rhythms? I will attempt to answer these questions in the sections below.