The very bizarre reason Ebony didn't know she was pregnant until she gave birth in a coma.

UK teenager Ebony Stevenson fell into a four-day coma after going to bed with a severe headache.

She’d become sick and began having seizures. She was rushed to hospital and just over three hours later, doctors performed an emergency caesarean.

When she woke up, the 18-year-old discovered she had given birth to a baby girl.

Her illness was caused by preeclampsia, but Ebony didn’t even know she was pregnant. She was still menstruating, had no morning sickness and hadn’t grown a bump.

This was because she had a condition called uterus didelphys, meaning she had two uteri.

Her baby was hidden in one uterus, which was positioned towards her back and meant no obvious baby bump. Ebony didn’t miss a period, because her menstrual cycle continued in the other uterus.

It’s a rare condition, occurring in approximately one in 3000 women according to gynaecologist and fertility expert Dr Sonya Jessup.

Dr Jessup told Mamamia it is an uncommon abnormality of the uterus and sometimes also the cervix and vagina.

“In a female foetus, the uterus develops when two mullerin ducts (two parallel tubes) fuse and the middle portion disappears to create a uterus. With this process women end up with one uterus, one cervix, one vagina and two ovaries.

“In some women this process fails to happen in the usual manner. There are many different variations of uterine abnormality ranging from a heart shaped uterus to a situation where a woman may have two uteri, two cervices, and a double vagina.”

Dr Jessup said uterus didelphys can be diagnosed by an ultrasound or speculum examination and often women will not recognise any abnormalities until they begin menstruation or become sexually active.

She said that in general, women with the condition are able to conceive spontaneously and usually the pregnancy will be in one uterine horn only.

There have been cases of women carrying multiple children in both uteri – such as UK woman Hannah Kersey who gave birth to triplets in 2003.

Two of her babies were identical twins born from one uterus, and her third was born from the other – it was believed to be a world first.

The Mayo Clinic stated uterus didelphys can create extra risks, such as miscarriage and premature birth, during pregnancy.

“In women with more severe version of UD up to 40 per cent will have breach presentation babies, 20 per cent of pregnancies may result in premature delivery,” Dr Jessup explained.

“Statistically caesarean section is performed in 80 per cent of women with UD. There can also be kidney abnormalities which may need to be checked for.”