A. Transvaginal sonographic measurements of the fetal crown rump length taken by a single experienced obstetric sonographer within a few seconds of each other show a calculated gestational age difference of 3 days. Discrete landmarks for measurement can be even more difficult to definitively determine during earlier gestations.
B. Crown-rump length consistent with 8 weeks and 6 days of gestation.
C. Crown-rump length consistent with 7 weeks and 0 days of gestation.
D. Crown-rump length consistent with 6 weeks and 1 day of gestation.
