A comparison of uterine motility in the pregnant and non-pregnant cynomolgus monkey (Macaca fascicularis) and pregnant woman: a manometric and electromyographic study.

: The use of a combination of manometric and electromyographic methods provided a reliable technique for evaluating variations in uterine activity in conscious macaque monkeys and women. The technique was particularly useful for obtaining data on the influence of steroid hormones. During the spontaneous menstrual cycle of the macaque, uterine motility, after being weak and poorly synchronized during the follicular phase, became still weaker with impaired synchronization during the luteal phase and then much stronger and well-synchronized at the time of menstruation. There was no evidence in vivo of any relationship between the existence of gap junctions in the myometrium of non-pregnant animals and the various patterns of uterine motility. During the last third of pregnancy in macaques, the initiation of electrical activity in various uterine areas was always synchronous with and related to mechanical contraction. The same results were obtained in preparturient women. Thus, improved uterine coordination does not appear to be the mechanism by which the uterine contractile strength increases to expulse the foetus at the end of pregnancy. Apart from the particular situation of non-pregnant animals under progestative influence, in which activity was constantly non-propagated, we could not find any evidence of a general pattern which would indicate only one site for the initiation of activity and its extension to the whole uterus.