Physiology: Utero-cervical inhibitory reflex. The description of a reflex and its clinical significance

The functional relationship of the uterine corpus to the cervixwas studied in 14 healthy women. The uterus was stimulated byan electro-myographic (EMG) needle electrode and the cervicalpressure recorded by a balloon-tipped catheter. The test wasrepeated in seven women after the uterus had been anaesthetized.In the other seven patients, the response of both the uterineEMG and pressure to cervical dilatation was registered. TheEMG needle electrode was then inserted into the cervix and theuterine pressure response to both stimulation and dilatationof the non-anaesthetized and anaesthetized cervix was recorded.Uterine muscle stimulation led to a cervical pressure drop froma mean of 15.8± 6.6 to 5.3 ± 2.2 cm H₂O (P<0.01). The cervical pressure did not respond to stimulationof the anaesthetized uterus. Cervical dilatation caused increaseof the uterine pressure from a mean of 16.2± 5.2 to 42.8± 10.5 cm H2O (P< 0.01), whereas cervical stimulationeffected a uterine pressure drop to a mean of 3.6 ± 1.8cm H₂O (P< 0.01). Stimulation or dilatation of the anaesthetizedcervix did not cause uterine pressure changes. The invariablecervical dilatation upon uterine stimulation suggests a reflexrelationship which we have named ‘utero-cervical inhibitoryreflex’ (UCIR). It seems that the reflex comes into actionduring labour and in conditions of uterine retention of bloodor a dead ovum. Its impairment may interfere with cervical dilatationor lead to cervical incompetence. The UCIR could be includedas an investigative tool in utero-cervical disorders.