DENVER (AP) _ Kathleen and Greg Miller were expecting quadruplets, so when the doctor said, ''Don't go away, there's one more,'' there was considerable commotion in the birthing room.

The surprise announcement was made by Dr. James Delaney as he rushed to deliver the babies by Caesarean section by midnight Monday so they'd have the same birthday. Because No. 5 was tucked high up near Mrs. Miller's rib cage, ultrasound had not detected it, he said.

All five, born 71/2 weeks early, made the midnight deadline and were doing very well Tuesday, hospital officials said.

Dr. David Belenky, the chief neonatologist at St. Joseph Hospital who specializes in critically ill newborns, said because the doctors and supplies were only set up for four babies, ''It took some scrambling to get ready for the fifth one.''

He said each baby had its own placenta, so they are not identical.

Mrs. Miller, 28, and her 29-year-old husband had been trying to have children for six years. She was taking a fertility drug when she became pregnant with the quintuplets.

''It's one of the greatest feelings that Kathy and I have ever had. We lost a baby last spring,'' Miller said at a news conference Tuesday. That baby died of toxemia, which is poisons or toxins in the bloodstream.

The first baby born Monday night was Joseph Gregory, at 11:55 p.m., weighing 3 pounds and 12 ounces. Michael Allen was next at 11:56 p.m, at 3 pounds, 10 ounces. Tyler Scott weighed 3 pounds and 3 ounces and was delivered at 11:57 p.m. Mallory Marie, 3 pounds, came at 11:58 p.m., and Timothy James, 3 pounds, 3 ounces, was the fifth at 11:58 p.m.

Belenky said the babies, who are in St. Joseph's intensive care nursery, are ''doing very well.''

Belenky said Mrs. Miller had been on Pergonal, a fertility drug. Delaney said that with Pergonal, the incidence of multiple births is 20 percent to 30 percent.

Mrs. Miller is a keypunch operator and Miller works at Ankovy Shadow Isle, a genetic center for breeding bulls at Watkins, about 18 miles east of Denver.