The Caesarean section rate in the United States reached 32 percent in 2007, the country’s highest rate ever, health officials are reporting.

The rate has been climbing steadily since 1996, setting records year after year, and Caesarean section has become the most common operation in American hospitals. About 1.4 million Caesareans were performed in 2007, the latest year for which figures are available.

The increases — documented in a report published Tuesday — have caused debate and concern for years. When needed, a Caesarean can save the mother and her child from injury or death, but most experts doubt that one in three women need surgery to give birth. Critics say the operation is being performed too often, needlessly exposing women and babies to the risks of major surgery. The ideal rate is not known, but the World Health Organization and health agencies in the United States have suggested 15 percent.

The continuing rise “is not going to be good for anybody,” said Dr. George A. Macones, the chairman of obstetrics and gynecology at Washington University in St. Louis and a spokesman for the American College of Obstetricians and Gynecologists. “What we’re worried about is, the Caesarean section rate is going up, but we’re not improving the health of babies being delivered or of moms.”