Just one month after delivering her first child, a Bangladeshi woman gave birth to twins who had been growing in a previously undiscovered second womb.

Key points: The woman had never had an ultrasound before

The woman had never had an ultrasound before She had a condition where the two tubes that form the uterus did not join up

She had a condition where the two tubes that form the uterus did not join up The couple think it's a "miracle" but will struggle to pay for their upbringing

In a case that has stunned the medical world, the woman, Arifa Sultana, 20, gave birth to healthy twins, a boy and a girl, about 26 days after giving birth to a premature baby boy.

Ms Sultana's case was a rarity, said Sheila Poddar, the chief of the gynaecology department at the Ad-Din Hospital in Jessore district where Ms Sultana underwent an emergency caesarean to deliver the twins.

"It's a rare incident. I have seen such a case for the first time. I hadn't even heard about such [an] incident before," she told local media.

Dr Poddar told the BBC that the couple were very poor and Ms Sultana had "never had an ultrasound before", so the double uterus came as a shock to all involved.

Dilip Roy, chief government doctor in the district, questioned why her second uterus wasn't detected by the hospital where she first gave birth.

"I haven't seen any case like this in my 30-year plus medical career," he said.

The couple, speaking to AFP, said the birth of three healthy babies was a "miracle", but they were concerned about how they would afford to raise the children, as Ms Sultana's husband earns barely $100 a month.

The condition of having two wombs, known as "uterus didelphys", is not unheard of.

In a typical case, the uterus begins in the female foetus as two ducts or tubes that join together to create one larger organ.

"Sometimes the two halves don't properly join," said Michael Permezel, professor emeritus at the University of Melbourne's Obstetrics and Gynaecology.

"Quite often they don't join completely and there are minor abnormalities of uterine shape. But this case, where there are two complete separate uteri, is very uncommon but not extraordinary — it's about one in a thousand women."

He said Ms Sultana's pregnancy was "an unusual variation on triplets".

Combining the likelihood of having two wombs with the probability of having triplets — one in 6,000 — made the likelihood of pregnancies like Ms Sultana's about one in 6 million, he said.

He said two wombs mostly didn't impact whether a woman was more or less fertile, although cases of miscarriage, or the baby being in breech, were slightly higher.

In 2010, an American woman, Angie Cromar, fell pregnant with a child in each uterus. They were conceived about a week apart.

Last year, a British woman, Jennifer Ashwood, gave birth to two children who were grown in two separate uteruses.