Nigerian twin girls joined in the chest and abdominal regions are now living virtually normal lives, weeks after being successfully separated at the state-owned National Hospital. Medical experts say the operation was the most complicated case of conjoined twins separation ever performed in Nigeria.

An event in Abuja to announce the successful separation of seventeen-month-old Nigerian twin sisters, Goodness and Mercy, starts on a celebratory note.

The mother of the twins, Mariam Martins, was not celebrating when she learned her girls were conjoined. She said their condition was undetected during pregnancy.

"None of the scans showed that they were joined. The doctors didn't know that they were joined, they only told me that they're in one place and using one placenta," she said.

After delivery through a cesarean section, the girls were referred to the National Hospital from the medical center here in Nassarawa, where they were born.

At the hospital, pediatricians and medical experts studied and nurtured them for a year before planning their separation.

During that period, Mariam said coming home without her babies was not easy.

"When I came back, I didn't want people to come and see me, I was ashamed of myself. I felt I had committed a big abomination. At that time I didn't know that it happens in some places, I thought I was the first. What have I done to be punished in this way. When people come to me, I feel they're mocking me...shame," she said.

The girls are the first conjoined twins to be successfully separated at the government-run specialist center.

The surgical separation of the twins, which lasted 13 hours, took place last November and was handled by a 78 -member medical team.

The girls were then monitored by hospital authorities for any post-surgery complications before finally allowed to go home in January.

Emmanuel Ameh is the pediatric surgeon who led the team.

"For them, the size of the liver that was there actually was the size of two livers joined together. In terms of separating it we had very advanced equipment that helped us to separate it very quickly without losing much blood," said the surgeon.

The conjoined twins phenomenon is extremely rare - approximately 1 in 200,000 births.

In the last decade, only 15 cases have been officially reported in Nigeria and the chances of survival for conjoined twins after separation are also usually slim.

Nigeria's health minister, Osagie Emmanuel, said the successful separation of the Martin twins is a testament for Nigeria's health system.

"We have demonstrated to ourselves that yes we can do it. And that demonstration will lift and increase the confidence in the health sector of this country," said Emmanuel.

Every year, Nigerian citizens spend millions of dollars to access health care abroad. Health authorities want to reverse that trend.

Successes like this could be the game changer.