Always first Identify the bladder by aiming into pelvis from just above pubic symphysis. Then identify the uterus directly adjacent to bladder. Once fetal pole is in view, find the longest axis and place calipers to measure crown rump length which works best in earlier gestations. Later gestations benefit from additional measurements like biparietal diameter, femur length, and head/abdominal circumference.
in a patient with a first trimester pregnancy gestational age dating can be accomplished very readily at the bedside with a couple quick maneuvers to do this scan i'm going to use the curvilinear transducer on an obstetrics preset i like to place the transducer in the transverse orientation just above the pubic bone and aimed deep into the pelvis to identify the bladder as my first landmark once i've confidently identified the bladder above the vaginal stripe i'll take the top of the transducer and start tilting it towards the feet until the uterus comes into view and ideally a fetus within it the easiest measurement for first trimester gestational age is the crown rump length so some maneuvering is required to really get the maximal pull of crown rump distance so i'll fan around and rotate until i feel confident that i've identified that and once i have i'll quickly freeze the scan sometimes singing back to find that best poll put on the calipers for crl and measure one pixel at the top and one pixel at the bottom to get my estimated gestational age in this case of 12 weeks two days i'll repeat the measurement at least two more times to get an average and feel very confident on my assessment of gestational age in the first trimester you
