Doctors in Houston, Texas, say ultrasound scans show the seven babies, born eight days ago, have no bleeding on the brain. Bleeding is an early sign of future developmental problems.

Four of the babies can now breathe unaided, although all seven remain in a critical condition.

The smallest of the octuplets died from heart and lung failure, a week after she was born.

The children are the first for Ms Chukwu and Mr Udobi, who live in Houston and both originally come from Nigeria. The couple had long tried to have children, before turning to fertility drugs.

Ms Chukwu entered hospital in early October and had been confined to bed for six weeks.

To keep pressure off her lower body she was put at an extreme incline with her head downwards.

According to the Guinness Book of World Records, the largest multiple birth was nine babies in Sydney, Australia, in 1971. All the children died.

Three other octuplet births have been recorded in the past 13 years, but in each case, some of the babies died.