I wonder if breastfeeding during pregnancy does increase oxytocin really. It really didn't feel that enjoyable to me lol
You definitely still produce oxytocin when breastfeeding during pregnancy, but not as much according to a study (Amico, J., and Finley, B., Breast stimulation in cycling women, pregnant women and a woman with induced lactation: pattern of release of oxytocin, prolactin and luteinizing hormone. Clinical Endocrinology, 1986 25:97-106)


One really important thing that my Obstetrician told me was that while oxytocin can cause mild contractions in any uterus, it's unlikely to cause preterm labour because the number of "oxytocin receptor sites" in the uterus does not increase dramatically until closer to the end of the third trimester. So oxytocin caused from breastfeeding is not likely to cause labour until the uterus is ready for birth anyway.