Dr. Beryl Benacerraf, a radiologist  who revolutionized the diagnosis of fetal abnormalities like Down syndrome through the use of ultrasound technology, died on Oct. 1, at her home in Cambridge, MA. She was 73.

Dr. Benacerraf, who was a professor of obstetrics, gynecology and reproductive biology and radiology at Harvard Medical School and Brigham and Women’s Hospital in Boston, discovered that a thickening patch of skin at the back of a fetus’s neck, known as the nuchal fold, was associated with Down syndrome and other chromosomal disorders.

In the course of her four-decade career, Dr. Benacerraf saw tens of thousands of patients while publishing hundreds of journal articles and several books.