Fetal crown-rump length and biparietal diameter in the second trimester of pregnancy.

This study examines the relationships between fetal size (biparietal diameter and crown-rump length) and gestational age among subjects aborted by hypertonic saline in the second trimester of pregnancy. With a confidence of 90 per cent, biparietal diameter can be used to predict gestational age within plus or minus 2 weeks, and crown-rump length can be used to predict gestational age within plus or minus 3 weeks.