The woman, who has not been identified, had a Caesarean section in 2015 at Luton and Dunstable University Hospital, and her twins then needed to be in an intensive care ward. The hospital confirmed the treatment cost £348,683.
It said in a statement: "This patient was an overseas visitor and was referred to us by another hospital because of complications with her twin pregnancy. As an NHS Trust we cannot refuse to treat a patient, wherever they are from, if there is a danger to life. In this case two unborn babies required immediate care.
"They were delivered safely but spent two months in our neonatal intensive care and high dependency units. This is the reason for the high cost and we are currently pursuing the patient for payment."
Freedom of Information requests by the Daily Mail to 90 hospitals also revealed that 13,077 overseas patients were treated in the UK in 2015/16, including 3,066 mothers who flew in to have their babies.
Imperial College in West London confirmed a debt of £319,895 for a woman who gave birth to triplets.
The hospital has also cared for a Nigerian woman with quads.
In December, Freedom of Information responses obtained by the Press Association revealed overseas patients have left the NHS with an unpaid bill of almost £30 million in just one year.
Patients who were not entitled to free treatment on the health service owed £29,530,378 in 2015/16.
More than 120 NHS trusts were asked to provide details on overseas patients who were billed for
NHS care and who were exempt from reciprocal arrangements with the UK.
Some 104 trusts across England responded, with the results suggesting the unpaid bill is rising year on year.
Of 92 trusts that were also able to give data for 2014/15, the outstanding debt in 2014/15 came to £15,907,018.