By Vicky Ntetema
BBC correspondent in Tanzania
The future of conjoined twins in southern Tanzania is uncertain because their lungs have been compressed by the weight of their bodies.
The six-year-olds, Maria and Consolatha, have separate heads and arms, and are joined from the navel downwards.
The twins are full of life
Their parents abandoned them after they were born and they have been in the care of Italian missionaries of Consolatha Fathers' Catholic Church in Ikonda village.
One of them has pulmonary problems, and doctors fear that this will affect her sister's life, should her situation get worse.
Father Christmas hats
But the girls do not share their doctors' fears, as they live their life to the full.
In their orange and red dress, with red and white hats, in the style of a Father Christmas hat, they smile showing their small white teeth with a few gaps indicating that they have lost four of their milk teeth.
"I removed them myself as they were shaking badly and became very very loose," Maria shyly tells me in Kiswahili.
The twins are about 14 inches high when they are positioned upright, with their legs lying flat on the floor. They can neither stand nor walk and when they want to move they can only slide on smooth surfaces using their bottom.
Eating for two
Their two legs are longer than the rest of the body.
Maria controls the movements of the right leg, while Consolatha controls the left.
Another short leg protrudes from their back, but it's non-functional.
They have two heads, two hearts and four arms.
And they share lungs, an abdomen, rectum and anus and urinary passage.
The health of Maria, who has had some breathing problems since birth, but who has a better appetite than her sister, Consolatha, is deteriorating.
Maria has been eating for the two of them until they were five-and-a-half, when Consolatha started to eat on her own.
She is now stronger and healthier than Maria.
Dr Rainer Brandl told BBC Network Africa that their lungs are sandwiched by their bodies, in such a way that they cannot expand.
Doctors can only hope and pray for the twins' lives, as they cannot separate them.
"When surgeons and consultants in South Africa and Europe were consulted, they said that it is not possible to separate them, because they are sharing organs like the liver, stomach, guts, and lungs, which means that one depends on the other," said Dr Rainer Brandl.
Dependency is the key word in their life because Maria tells me that when Consolatha wants to go to toilet, Maria would know and inform their carer and vice versa.
"We just know it and accompany each other to the toilet," says Consolatha.
Beating the odds
Maria and Consolatha started school this year.
The hospital's matron, Italian Sister Magda Boscolo, says that the twins have different personalities.
Both are very intelligent and strong and that they have beaten all the odds to reach school age.
"When they were born we did not think that they would survive the next day. Now we need to make their lives more comfortable," says Sister Magda.
The girls need regular exercises and the understaffed hospital cannot cope with it.
It has employed a fulltime worker for round-the-clock care.
But because of the weight of the children, four more assistants are required to look after the twins during the day.
They have been recently moved from the hospital to a private house of Bertina Mbilinyi, to be near their school.
Maria says she wants to become a doctor so that she can treat people with headaches and stomach problems and Consolatha wants to become a nun, so she can take care of orphans the way the Italian sisters have taken care of them.
Mrs Mbilinyi, a divorced mother of two teenager boys and who has known the twins from their infancy, says that the twins do not regard themselves as different from the other children in the area.
And their schoolmates treat them as such.
They play with them and help Mrs Mbilinyi with the wheelchair as she takes the girls up the hill to school.
"The children are getting heavier and heavier as they get older and I am not getting younger," she said.
"What they need is a special bigger and stronger modern wheelchair," she adds.
'Full of life'
So do the girls ever quarrel?
"When Maria cannot find her pencil, she pinches and slaps me, accusing me of stealing it," complains Consolatha.
But they quickly make it up and forgive each other, says Maria, with a twinkle in her eye.
The girls are so full of life that they even want to show me their dance. They choose a track from their piano and dance.
They swing from side to side using their hands as legs and dragging their legs to move about in a well choreographed style, swinging their heads from one side to another, according to the rhythm.
But Maria is now breathing heavily and getting tired. And Consolatha knows when to stop for her sister to rest.
As I leave they invite me to their seventh birthday on 19 November. And I wouldn't miss it for anything in the world.