Questioning the role of pituitary oxytocin in parturition: spontaneous onset of labor in women with panhypopituitarism--a case series.

OBJECTIVE: Oxytocin, a nanopeptide secreted by the posterior pituitary gland, has well-established uterotonic activity. Its role in initiating the vigorous and regular contractions of the first stage of labor is still controversial. We report four cases of panhypopituitarism who had spontaneous onset of labor, undermining the role of maternal oxytocin in the first phase of labor.

STUDY DESIGN: Four women with no residual pituitary function conceived through ovulation induction and were treated throughout pregnancy with thyroid replacement therapy, desmopressin and glucocorticoids. In all cases pituitary function was undetectable in repeated blood tests. We report their course of pregnancy and delivery.

RESULTS: All four pregnancies progressed to term with hormonal replacement therapy. All cases went into spontaneous labor. Two women delivered vaginally unassisted by pharmacological intervention and two delivered by cesarean sections during active labor due to obstetrical indications. Three suffered postpartum hemorrhage. Lactation did not ensue in all four cases.

CONCLUSIONS: Endogenous pituitary oxytocin is probably not obligatory for initiation of labor in the first phase of parturition.