Side effects with oxytocin are not common. Serious side effects include:
an allergic reaction (shortness of breath; closing of the throat; hives; swelling of the lips, face, or tongue; rash; or fainting);
difficulty urinating;
chest pain or irregular heart beat;
difficulty breathing;
confusion;
sudden weight gain or excessive swelling;
severe headache;
rash;
excessive vaginal bleeding; or
seizures.