The birth of seven babies, one stillborn and the rest still in danger, to a California woman this week could likely have been prevented by careful monitoring of the fertility drugs taken to stimulate the pregnancy, a drug company spokesman said today.

Michael Rinaldo, a New York-based spokesman for Ares-Serono Inc., manufacturer of the fertility drug Pergonal, said the Boston-based company was not at fault for the unplanned conception of septuplets, which forced Patricia Frustaci to give birth 12 weeks prematurely.

Dr. Martin Feldman, the Orange County, Calif., obstetrician who delivered the babies Tuesday, has said she was given Pergonal at the Tyler Medical Clinic Inc. in West Los Angeles. A woman who answered the telephone at the clinic today declined to respond to questions about the case. "There are no guarantees with some of these drugs," she said.

Although Pergonal is known to stimulate the follicles in the ovaries, which can lead to the release of an unusual number of eggs and thus multiple pregnancies, a Norfolk, Va., expert on human reproduction said the chances of having septuplets could be minimized.

Dr. Zev Rosenwaks, director of the Jones Institute for Reproductive Medicine, said daily estrogen measurements and daily sonographic examinations can determine if an unusual number of follicles has been stimulated. If so, he said, doctors can suspend the procedure and try again in a few weeks. Usually the follicles will not release eggs for fertilization until a second drug, human chorionic gonadotropin, is administered, he said.

According to a news release from Saint Joseph Hospital, where the babies were born, Ares-Serono has reported 20 percent of Pergonal patients having two or more babies at a time; 5 percent of Pergonal patients will have pregnancies resulting in three or more babies. Frustaci, 30, and her husband Sam, 32, have a 14-month-old son who was also born after she took Pergonal.

Dr. Carrie Worcester, chief of the neonatal intensive-care unit at Childrens Hospital of Orange County, said that Baby A, one of the two surviving girls, was greatly improved today and that Babies B, C and E, three of the four boys, had shown some improvement. Baby D, the other girl, had improved only slightly, and Baby F, by far the smallest at only about one pound, had shown no change.

Tes Pane, obstetrical nursing director at Saint Joseph, said the mother seemed astounded when she got her first long look at the babies this morning by watching news broadcasts. "She asked me, 'Are these really my babies?' " Pane said.

Patricia Frustaci was unconscious during the three-minute Cesarean delivery and has been allowed to see and hold only the 15.5-ounce girl who was stillborn.

Sam Frustaci and the couple's attorney, Andrew Wallet, have been busy the past two days receiving offers of products and money, as well as negotiating the publication rights to the story.

Although at least six sets of sextuplets are known to be alive in the world, no more than five babies born to one woman at the same time have ever survived in the United States.

All six Frustaci newborns weighed less than two pounds. In critical but stable condition, they have been given a 50 percent chance of survival by Worcester.

Their most crucial problem is their immature lungs, which must be aided by a respirator.

Each also suffers from jaundice due to an immature liver and from the failure of a duct between the aorta and the pulmonary artery to close properly.