Browse the corpus
Walk the Even Hospital Database by book and chapter — the raw source passages that ground Ask, DDx, and the rest.
1 passage
©2013 UpToDate ® Print Email Assessment of gestational age Parameter Gestational age, weeks Accuracy, days Mean sac diameter 4.5 to 6 ± 5 to 7 Crown-rump length 7 to 10 ± 3 10 to 14 ± 5 15 ± 8.4 Biparietal diameter, head circumference, femur length 14 to 20 ± 7 21 to 30 ± 14 over 30 ± 21 to 28 The American College of Obstetricians and Gynecologists suggest using the sonographically derived gestational age to calculate estimated date of delivery (EDD) if it differs from that calculated using the LMP by more than seven days in the first trimester and by more than 10 days in the second trimester but before 20 weeks of gestation. ACOG Practice Bulletin No. 98: Ultrasonography in pregnancy. Obstet Gynecol 2008; 112:951.