Oxytocin given in high doses, or to women who are hypersensitive to it, may cause uterine hyperstimulation with hypertonic or tetanic contractions, leading to uterine rupture and soft tissue damage. Effects in the fetus include bradycardia, arrhythmias, asphyxiation and perhaps death.
Maternal deaths from severe hypertension and subarachnoid haemorrhage have occured. Rapid intravenous injection of Oxytocin has produced acute transient hypotension with flushing and reflex tachycardia. Postpartum haemorrhage, fatal afibrinogenaemia and disseminated intravascular coagulation have been reported, but may be due to complications of labour induction rather than Oxytocin itself.
High doses of Oxytocin infused over prolonged periods can also cause water retention leading to hyponatraemia and intoxication, which may progress to convulsions, coma, and even death. Vasopressin-like activity is more likely with Oxytocin of natural origin but may occur even with the synthetic peptide. Other adverse effects include headache, nausea and vomiting, skin rashes, cardiac arrhythmias, pelvic haematoma and anaphylactic and other hypersensitivity reactions.
There are reports of neonatal jaundice and retinal haemorrhage associated with the use of Oxytocin in the management of labour.