Doctors say quadruplets born prematurely a month ago to a 65-year-old woman in Germany are doing well and gaining weight but one remains on a respirator.

Berlin's Charite hospital said Wednesday the four babies — a girl named Neeta and three boys named Dries, Bence and Fjonn — have put on 30 to 50 percent of their birth weights since they were delivered by cesarean section on May 19.

The hospital says one has been taken off a respirator but another still needs help breathing.

Annegret Raunigk is believed to be the oldest woman to have ever delivered quadruplets.

The retired schoolteacher already has 13 other children aged 9 to 44 from five fathers. She traveled abroad to have donated, fertilized eggs implanted — a procedure that's illegal in Germany.