Oxytocin-induced uterine hypercontractility pressure wave forms.

To identify similarities and differences between uterine contractions in patients with spontaneous labor, oxytocin-corrected hypocontractility, and oxytocin-induced hypercontractility, measurements were made of specific characteristics of the intrauterine wave form, including pressure, rate of change of pressure, and duration. Contractions from oxytocin-treated patients differed from contractions of those with spontaneous labor in their disproportionately high rates of rise of the pressure. The time to reach the maximum rate of the pressure--the start-up time--was reduced in oxytocin-induced hypercontractility. The data demonstrate that the contractions of spontaneous labor and oxytocin-augmented labor are not identical, and the physiologic implications are discussed.