Uterine effect of cervical buffeting: role of the cervicouterine reflex in coitus.

OBJECTIVE: To investigate the hypothesis that cervical buffeting during coitus effects reflex relaxation and dilatation of the corpus uteri (CorU) smooth muscle; that mechanism acts to suck the ejected semen into the CorU. STUDY DESIGN: The CorU response to electrical and mechanical stimulation of the CU was recorded in 22 healthy women (mean age, 38.2 +/- 7.6 SD years). Cervical electrical stimulation was effected by an electromyographic needle electrode and mechanical stimulation by pencil electrode. The test was repeated after individual anesthetization of the CU and CorU and after normal saline injection. RESULTS: Slow waves, superimposed or followed by action potentials, were recorded at rest from the CorU electrode. Electrical or mechanical stimulation of the CU effected a significant reduction of the electric wave parameters and pressure in the CorU; this response was reproducible. Separate stimulation of the anesthetized CU or CorU did not evoke the response, while saline infiltration did. CONCLUSION: CU stimulation resulted in diminished CorU electrical activity and pressure; that presumably indicates uterine wall relaxation. Repeated CU buffeting apparently leads to an intermittent uterine pressure decline, with resulting semen siphonage from the vagina to the uterus. Diminished CorU electrical activity and pressure on cervical stimulation or buffeting might be mediated through the cervicouterine inhibitory reflex. This reflex seems to be evoked by penile thrusting during coitus and may prove of diagnostic significance in sexual disorders.