The effect of an intra-uterine device on uterine motility in women and rhesus monkeys.

PRESENT understanding of human female reproductive physiology has largely been derived from the results of animal experimentation, and particularly from studies on the rhesus monkey. This is also true of our present knowledge of the possible modes of action of an intra-uterine device (IUD). Recent studies in the rhesus monkey have shown that an intra-uterine device is contraceptive in this species (Kelly & Marston, 1967; Kelly, Marston & Eckstein, 1969). The periodicity of the menstrual cycle is not affected by the presence of an IUD (Eckstein, Kelly & Marston, 1969), and the processes of ovulation, sperm transport, fertilization and early embryonic development within the Fallopian tube are not disturbed (Kelly et al., 1969; Marston, Kelly & Eckstein, 1969a; Mastroianni et al., 1967). The principal contraceptive effect of an IUD in the rhesus monkey is most probably exerted within the uterus by premature expulsion, destruction or failure to implant of the fertilized egg. Clinical studies suggest that in women, too, the processes of sperm transport (Malkani & Sujan, 1964; Morgenstern et al., 1966) and tubal transport of the egg (World Health Organization, 1966; Noyes et al., 1966) are not affected by the presence of an IUD. The contraceptive action of an IUD in women appears to be exerted within the uterus, and may be related to a disturbance in the normal pattern of uterine motility. This possibility has been tested by Bengtsson & Moawad (1966, 1967) and Johnson, Ek & Brewer (1966) who employed the intra-uterine, open-ended catheter technique devised by Hendricks (1964). Behrman & Burchfield (1968) have used an IUD with a built-in, pressure-sensitive transducer to record the direct effect of myometrial activity on the IUD. Johnson et al. (1966) studied post-partum women at the time of IUD insertion and again 2 weeks later. They found no differences between their two