Before revision: A study of singleton live births came to the result that childbirth has a standard deviation of 14 days when gestational age is estimated by first-trimester ultrasound and 16 days when estimated directly by last menstrual period.
After revision: A study of singleton live births determined that childbirth has a standard deviation of 14 days when gestational age is estimated by first-trimester ultrasound and 16 days when estimated directly by last menstrual period.