( CNN ) -- A woman in California delivered what may be the nation 's second live-born set of octuplets on Monday morning , surprising doctors who expected seven babies . Members of the delivery team assigned to assist in the birth of the octuplets , just minutes before the delivery . The six boys and two girls -- ranging in weight from 1 pound 8 ounces to 3 pounds 4 ounces -- were generally doing well in incubators following their Caesarean-section delivery at Kaiser Permanente hospital in Bellflower , California , doctors said . Three of the babies need breathing assistance , but otherwise the eight do n't appear to have serious problems , doctors said at a news conference Monday evening . `` It was a truly amazing delivery , '' said Dr. Karen Maples , chief of the hospital 's obstetrics and gynecology department . Doctors initially believed the mother -- whom they did not identify -- was pregnant with seven fetuses . The woman was 23 weeks pregnant when she was hospitalized seven weeks ago and ordered to bed rest . Over a seven-week period , a team of 46 physicians , nurses and other staff prepared for the births . When they started the delivery Monday -- more than nine weeks before the babies would be full term -- they were in for a surprise . `` After we got to Baby G , we were surprised by the discovery of a Baby H , '' Maples said . Getting the number correct with ultrasounds before delivery is difficult with so many babies , said Dr. Harold Henry , the hospital 's chief of fetal medicine . `` It is quite easy to miss a baby when you 're expecting seven , '' Henry said . The hospital said the woman did n't want her personal information released to the news media , and it would not answer questions about whether she 'd had fertility treatments . Preliminary research indicates this is the second set of live-born octuplets in the United States , according to the hospital . Eight babies believed to be the United States ' first set of live octuplets were born in Houston , Texas , in 1998 . One of the infants died days after birth . The seven other siblings recently celebrated their 10th birthday , the Houston Chronicle reported last month . The first three to seven days will be critical for the California babies , said Dr. Mandhir Gupta , one of the doctors at the news conference . The infants could be in incubators for six to eight weeks and in the hospital for 10 weeks , Gupta said . The mother is doing `` very well '' after the deliveries , which took about five minutes , Gupta said . `` She is very excited that she [ has ] all these babies and that the babies are looking good so far , '' Gupta said .
Babies may be U.S. 's second set of live-born octuplets , California hospital says . Doctors expected seven babies , did n't know of eighth until delivery . Octuplets delivered by Caesarean section Monday morning . Three require breathing assistance ; next seven days will be critical , doctor says .