Role In Maintenance Of Pregnancy Research Articles

Failure of progestogens to prolong pregnancy in the guinea pig.

PROGESTERONE treatment in cases of threatened abortion and premature labour has been of little therapeutic value1–3. These rather unexpected results, in view of the now classical work of Corner and Allen4,5, have brought into question the plausibility of the “progesterone theory for the maintenance of pregnancy” when applied to the human being6. Recent development of the concept of the local action of progesterone7–10, however, has provided grounds for considering pregnancy maintenance in terms of a ‘basic mechanism’11, which allows for species variation with regard to ovariectomy and response to oxytocin and progesterone treatmen. This theory states that the significant physiological level of progesterone in the uterus is a function of placental progesterone which diffuses directly to the myometriu. Under these conditions the systemic progesterone-level assumes a proportionately less important role in pregnancy maintenance. According to this theory, then, the local concentration gradient of progesterone in the myometrium surrounding the placenta results in asynchronous activity9 and a general lowering of excitability, conduction and pharmacological reactivity12, hence the local progesterone ‘block’ to the onset of parturition7.