Hong Wei was born with an extra thumb on his right hand
By James Reynolds
BBC News, Shanxi, central China
For the Li family, the best part of the day comes at noon.
Every day, after school, Li San San picks up his children from school, jams them all onto the back of his motorbike and drives them through the hills back home.
The kids cling onto each other and laugh as they try not to fall off.
On the main roads nearby, lines of coal trucks head off to the rest of China. The valleys are full of steelworks and heavy industry.
The Li family get back to their home, which is carved into the side of a hill.
Six-year-old Hong Wei eats his noodles and sits quietly in front of his school notebook.
He has a shy smile and hides in his sister's lap when we try to talk to him.
Hong Wei was born with an extra thumb on his right hand. His elder sister Lixia, who's 14, was born with a twisted left foot and walks with a heavy limp.
Like many people in Shanxi, this family is too poor to go to the doctors. The parents don't know why their children were born with defects. They're simply left to guess.
"The air isn't good around here," says Li San San. "When it's bad, it's difficult to breathe, it looks gloomy and smoggy out there."
The province of Shanxi is one of the most polluted places in the world.
James Reynolds reports from Shanxi in central China
The rate of birth defects in this region is six times higher than the national average.
In January, the director of family planning in Shanxi, An Huanxiao, told the China Daily newspaper that the province's high rate of birth defects was related to environmental pollution.
But doctors we spoke to in Shanxi are more sceptical.
One doctor at a village clinic told us that a local survey carried out in 2002 concluded that birth defects were caused by malnutrition.
As a result, he said that the authorities decided to distribute enriched flour to poor families in the area.
Poor medical care
At the Zhong Yang county maternity hospital, also in Shanxi, there's a view that malnutrition is as much to blame as pollution.
A poster on the wall encourages pregnant mothers to eat well.
Zhao Shuzhen, 23, has come in for an ultrasound as she is nine months pregnant.
"This is my first baby so we want to know whether or not the kid will be okay," she says. "My husband was worried so we discussed it and decided to come to the hospital."
The Zhang family, in the village of Gao Jiagou, has never had the benefit of proper medical attention.
The family's two eldest children, 13-year-old Yi Mei and 9-year-old Yi Long were both born with mental disabilities.
Yi Long is unable to talk. Yi Mei can only say one word and spends the day listening to music on a mobile phone.
It's too early to tell whether new born Yi Wu is healthy
Their mother has just given birth to a third child, Yi Wu.
The new baby lies under a blanket in the middle of the only bed in the house. A cardboard box is propped up behind his pillow.
His mother believes it's too soon to tell for sure whether or not Yi Wu has been born without any disabilities.
But she keeps looking at him, hoping for signs that he is okay.
"When I look at him he seems alright," she says hopefully.
She wants him to be a doctor when he grows up.
China has promised to clear up its air and water, but in this province, industry comes before a cleaner environment.
And in the grime of this one house in Shanxi, the hopes of an entire family rest on one baby.