Results
For each practitioner, we analyzed 15 cases from the second trimester and 15 from the third trimester for the three periods, i.e ., 90 cases per practitioner, which represented 300 cases before 2016, 300 in 2017, and 300 in 2020, making a total of 900 cases.

Inclusion of LVOT images

In our study, of the 900 files analyzed, there were no images relating to the LVOT in 51 (5.7%) of the cases. These files were therefore given a score of 0. These included 14 (4.7%) before 2016, 17 (5.7%) in 2017, and 20 (6.7%) in 2020; 34/360 (9.4%) were taken from files extracted from the database of the Saint Joseph hospital and 17/180 (9.4%) from the Var center. For the Saint Joseph’s Hospital, LVOT images were absent in 8/120 (6.7%) before 2016, 11/120 (9.2%) in 2017, and 15/120 (12.5%) in 2020. For the Var center, LVOT images were absent in 6/60 (10%) before 2016, 6/60 (10%) in 2017, and 5/60 (8.3%) in 2020. In total, 25/450 (5.6%) images were documented to be absent in the second trimester and 26/450 (5.8%) in the third trimester. Thus, images of LVOT were present in 95.3%, 94.3%, and 93.3% of cases before 2016, in 2017, and after 2020, respectively, for the three centers combined.
In order to make our analysis of practices more meaningful, we deliberately chose to exclude all files without an LVOT image. We therefore restricted our study to files with an image of the LVOT in order to shed more light on the use, or otherwise, of the proposed quality criteria.

Total average scores for the three centres over the three periods

The average total scores for the quality criteria across all centers were 5.49/7 (95% CI: 5.36-5.62), 5.91/7 (95% CI: 5.80-6.03), and 5.70 (95% CI: 5.58-5.82) for study periods before 2016, in 2017, and after 2020, respectively.
There was a significant difference between the scores obtained before 2016 and in 2017 (p < 0.001) and also between the scores before 2016 and in 2020 (p = 0.039). There was no significant difference following the introduction of the quality criteria; 2017 vs. 2020, p = 0.054 (Figure 2).

Average scores according to trimester

Score averages were 5.75/7 (95% CI: 5.65-5.85) and 5.65/7 (95% CI: 5.55-5.75) in the second and third trimester, respectively(Figure 3) .

Average scores according to cardiac position

In Position 1 (with the back at between 12 o’clock and 3 o’clock), the average score was 5.59/7 (95% CI: 5.45-5.73). In Position 2 (back between 3 o’clock and 6 o’clock), the average score was 5.99/7 (95% CI:5.87-6.10). In Position 3 (back between 6 o’clock and 9 o’clock), the average score was 5.82/7 (95% CI: 5.65-5.98). In Position 4 (back between 9 o’clock and 12 o’clock), the average score was 5.33/7 (95% CI: 5.19-5.48) (Figure 4 ).
Comparing the score averages obtained according to the position of the back of the foetus, we found a statistically significant difference between Positions 1 and 2 (p <0,01), between Positions 2 and 4 (p <0,01), and between Positions 3 and 4 (p < 0,01).

Average scores according to centre for the three periods combined

The average score at the GHSR was 5.90/7 (95% CI: 5.8-6), at the Saint Joseph’s Hospital 5.41/7 (95% CI: 5.29-5.53), and at the Var center 5.83/7 (95% CI: 5.69-5.98) (Figure 5 ).
We note a significant difference between the scores from Saint Joseph’s Hospital and the GHSR, but also between Saint Joseph’s Hospital and the Var center (p < 0.01 for each). There was no significant difference between average scores from the GHSR and the Var center (p =1).

Average scores according to centre for each of the three periods

The average scores for the three centers over the three periods studied are summarized in Figure 6 .

At the GHSR

Before 2016, the average score was 5.67 (95% CI: 5.49-5.85), in 2017 5.96/7 (95% CI: 5.78-6.14) and in 2020 6.08/7 (95% CI: 5.90-6.26).

At Saint Joseph’s Hospital

Before 2016, the average score was 5.25/7 (95% CI: 5.06-5.44), in 2017 5.76/7 (95% CI: 5.57-5.95) and in 2020 5.21/7 (95% CI: 5.02-5.40).

At the Var centre

Before 2016, the average score was 5.57/7 (95% CI: 5.30-5.84), in 2017 6.11/7 (95% CI: 5.84-6.38) and in 2020 5.82/7 (95% CI: 5.55-6.09).

Average scores according to operator for the three periods combined

Average scores for the 10 practitioners in the three centers over the three periods combined are summarized in Figure 7 .

At the GHSR

The total average for Practitioner A was 5.63/7 (95% CI: 5.43-5.84), and for Practitioner B was 6.03/7 (95% CI: 5.85-6.22). The total average for Practitioner C was 5.79 (95% CI: 5.58-5.99), and for Practitioner D was 6.16 (95% CI: 5.95-6.36).

At Saint Joseph’s Hospital

The total average for Practitioner A was 5.45/7 (95% CI: 5.23-5.68), and for Practitioner B was 5.24/7 (95% CI: 4.98-5.51). The total average for Practitioner C was 5.37/7 (95% CI: 5.10-5.64), and for Practitioner D was 5.54/7 (95% CI: 5.31-5.77).

At the Var centre

The total average for Practitioner A was 5.59/7 (95% CI: 5.35-5.84) and for Practitioner B was 6.03/7 (95% CI: 5.87-6.20).

Average scores according to practitioner for each of the three periods

Average scores for the 10 practitioners over the three periods studied are summarized in Figure 8 .

Individual study of the seven quality criteria (%)

The percentage of quality criteria considered in all three periods combined and according to the position of the back of the foetus is summarized in Table 1 .
Consideration of the seven quality criteria over the three periods studied and according to the position of the back of the foetus is summarized in Figure 9 and Figure 10,respectively.

Variability

The intra-class correlation coefficient (ICC) for intra- and inter-operator agreement between the junior doctor (MR) and expert doctor (EQ), with and without 0 scores, is presented in Table 2 . All ICCs were between 0.601 and 1.