Oxytocin secretory response to breast stimulation in pregnant women

Plasma oxytocin levels were measured serially in 10 pregnant women prior to labor and 16 women during labor in response to 12 minutes of Egnell breast pump stimulation. There was no increase in plasma oxytocin concentrations during either the second or third trimesters in 24 of the 26 subjects studied. Five minutes of manual autostimulation of the breast in 10 additional women at term also had no effect on plasma oxytocin levels.