HOUSTON (Reuters) - The world‘s only surviving octuplets, born prematurely to a 27-year-old woman who took fertility drugs, fought for their lives on Monday in a Texas hospital. Two of the eight babies were said to be in worse shape than the others and were receiving oxygen, but all were in critical condition at the neonatal intensive care unit at Texas Children‘s Hospital. Seven were on ventilators to help them breathe. "It‘s really too early to say (what the prognosis is)…. They are all critically ill. Several have shown some improvement and several haven‘t," said Leonard Weisman, the hospital‘s chief of neonatology service. He said statistically the babies had an 85 percent chance of survival and a 75 to 80 percent chance of developing normally. Their hospital stay, expected to last at least two months, will cost about $250,000 each, Weisman said. The babies, six girls and two boys as yet unnamed, weighed between 10 ounces (320 grams) and 26 ounces (810 grams) at birth. One of the girls was born normally on Dec. 8, 12 weeks premature. But labour was delayed and the other seven were delivered by caesarean section, 10 weeks premature, on Sunday. The mother, Nkem Chukwu, had to undergo emergency surgery in the night to stop internal bleeding, but was in stable condition, said obstetrician Brian Kirshon. He said the haemorrhaging was caused by the medication Chukwu took to prolong her pregnancy. Chukwu entered the hospital in early October and took extraordinary measures to maintain her pregnancy so the babies would have a better chance of survival, including reclining virtually upside down the last two weeks to keep pressure off her cervix. She also turned down an offer to abort some of the foetuses to increase the odds of survival for the rest. Father Iyke Chukwu, a respiratory therapist at a Houston hospital, was not present when the babies were born, but visited his wife on Monday. The couple are U.S. citizens from Nigeria who now live in Houston. Kirshon said Chukwu would likely go home in a week, where she may eventually face the prospect of raising eight children. Chukwu and her husband had been trying to have a baby for some time and finally resorted to drugs to stimulate egg production. She first conceived triplets, but miscarried them earlier this year. Doctors knew she had "numerous" foetuses in her womb, but did not realise there were eight until after the first one was born and they could get a better view with a sonogram, said Kirshon. He said they became concerned one of the foetuses was not getting enough blood and were considering inducing birth when Chukwu went into labour on her own on Sunday. As many as 28 people, including eight physicians, were involved in the birth on Sunday. Weisman said the use of fertility drugs had increased the number of multiple, premature births nationally — a trend he called "alarming." He said about 25 of the 60 babies currently in the neonatal intensive care unit at Texas Children‘s Hospital were born prematurely. The octuplets top the previous record of seven surviving babies born on Nov. 19, 1997.