Table 5. Mean difference with the reference GA (days) that was estimated using the CRL in the first trimester.

	Trimester 1	Trimester 2	Trimester 3
Observer 1	0.8±2.6	-0.0±4.6	1.9±11.0
Observer 2	1.6±2.7†•°	2.0±4.8*•°	3.9±13.7
System A	2.5±11.2	0.6±4.7†•°	2.9±12.5
System B	0.6±4.3	0.6±4.9†	3.8±14.4°
System C	0.6±4.3	0.4±4.7†	2.5±12.4

Note:

^†significantly different from observer 1,

*significantly different from system A,

^•significantly different from system B,

°significantly different from system C