When married couples are given the choice between surgical sterilization or birth control pills as a method of contraception, a higher percentage opt for surgery, a health study showed. The National Center for Health Statistics said the number of married men and women who chose shortly after childbirth to have an operation to prevent future pregnancies rose from 7.8%, or 220,000, in 1972 to 11.3%, or 330,000, in 1980, a relative increase of 45%, the report said. In 1982, about 7.9 million married women--not just those who had recently given birth--relied on sterilization as their contraceptive method, officials said. The percentage of married black mothers who were sterilized nearly doubled from 9.8% in 1972 to 19.2% in 1980, a relative increase of 96%. Among married white mothers, the percentage sterilized increased from 7.7% to 10.5% over the same period, a relative increase of 36%.