... and tetanic uterine contractions (convulsions) and also from chills and low blood pressure.

At the time our first child was born the story started with vomiting and chills right after connecting of the Syntocinon infusion. The first day was very hard to endure and the next days breastfeeding caused these symptoms again. After a few days of breast pumping the symptoms disappeared and she breastfeeded our first child for more than a year.

At the time our second child was born she got no infusion. During labor she vomitted a little only. The same symptoms came after giving birth the placenta and they were more intense and lasted for a longer time. Even when it seemed everything is okay again on the fifth day the story restarted after a day of breastfeeding -- we had to go back to the hospital due to continous vomiting, my wife could not drink at all. After a few days of breast pumping again and gradual return to breastfeeding the symptoms are gone.

Is it an allegated hypersensitivity to Oxytocin? If yes, is there any available studies on the production, emptying and decay rates of Oxytocin related to childbirth and breastfeeding?
Is there anything else to suspect?
What can we do about the next time?