Dr. Louis K. Diamond, 97, the pediatric hematologist who in 1932 recognized and first described the problem of blood group incompatibility between mother and unborn child commonly known as the Rh factor, died June 14 at his home here. The cause of death was not reported.

Dr. Diamond, a past president of the American Pediatric Society, worked for three universities during his 60-year academic career. He also helped organize the national Red Cross system for blood donations and collection.

"He was the founding father of the discipline of pediatric hematology," said Stephen Feig, professor of pediatrics at the University of California, Los Angeles. "He put it on the map."

After immigrating from Russia at age 2, Dr. Diamond grew up in New York. He graduated from Harvard University in 1923 and its medical school in 1927. He was barely out of medical school when he started one of the first pediatric hematology research laboratories in the country at Children's Hospital in Boston.

In 1930, he recognized and described thalassemia, a hereditary anemia, in Greek and Italian children in Boston. He also began studies of childhood anemias that identified the importance of iron deficiency in the diet--an inquiry into nutritional anemias that continued into the 1960s, when he focused on kwashiorkor, a disease of protein-starved children in Africa, the Middle East and Latin America.

In 1932, Dr. Diamond published his classic paper describing as a single entity the four newborn hemolytic diseases now known as erythroblastosis fetalis. The diseases were later found to result from the blood group incompatibility of a Rh-negative mother and her Rh-positive fetus.

Douglas Starr, in his 1998 book "Blood: An Epic History of Medicine and Commerce," credited Dr. Diamond with solving the blood incompatibility problem in 1946 through whole-body blood transfusions. Dr. Diamond discovered he could withdraw the fetus's affected blood bit by bit through the umbilical cord, and substitute it with blood compatible with the mother's. Now replaced by Rh vaccines, Dr. Diamond's method was in use for many years and reduced the mortality of the disease from 50 percent to less than 5 percent, saving the lives of 20,000 babies a year.

At least two other diseases of the blood bear the doctor's name: Diamond-Blackfan syndrome, a rare congenital anemia in children first described in 1938, and Gardner-Diamond syndrome, an unusual autoerythrocyte sensitivity that affects young women, described in 1950.

Dr. Diamond also participated in the first use of chemotherapy in childhood leukemia.

He spent 41 years at Harvard University medical school, where he served as professor of pediatrics, head of hematology and associate physician-in-chief at the Children's Hospital Medical Center in Boston.

After he reached Harvard's then-mandatory retirement age of 65, he moved to the University of California at San Francisco as professor of pediatrics. In 1987, he transferred to UCLA as an active professor emeritus, remaining active into his nineties.

His wife of 70 years, Flora, died last year. Survivors include two children, both of Los Angeles, a sister and four grandchildren.