## 3 Results  
A total of 33 sonographers were recruited in this study. The participants' years of experience were categorised into three groups, with Group 1 having \(\leq\)3 years of experience (n = 12), Group 2 having 4 to 10 years of experience (n = 9), and Group 3 having more than 10 years of experience (n = 12). The results indicated that the participants' confidence in assessing the PCI and their ability to spatially visualise the placenta and PCI for all PCI classifications, pre-demonstration, was higher than average (mean = 2.5). The association between years of experience and all responses, except for \"ability to spatially visualise placenta and PCI while performing ultrasound and \"ability to spatially visualise placenta and MCI while performing ultrasound\", was statistically significant (Table 1). It is noted that the mean rating for both the confidence and spatial awareness decreased with increasing PCI complexity. We further analysed the data to establish relationships between the grouped years of experience and participants' responses. There was a significant association between a sonographer's experience level and (i) their confidence in assessing the PCI and (ii) their ability to spatially visualise the placenta and PCI, with those sonographers in group 1 (least experienced participants) being less confident and less able to spatially visualise the placenta and PCI than those in group 2 (\(p\)-values < 0.05 for all PCI types). There was no significant association when comparing groups 2 and 3 (Table 2). Following the demonstration, participants were asked to rank the 2D ultrasound images, 2D ultrasound videos, and 3 DPMs from 1 to 3 (with 1 being least helpful and 3 being most helpful) to determine which method of PCI demonstration was the most effective in terms of spatially visualising the PCI. The results showed most participants found the ultrasound images to be the least useful method for spatially visualising the \begin{table}
\begin{tabular}{l l l l} \hline
**Question** & **Mean (SD)** & \(p\)**-Value** & **Effect Size \(\eta^{2}\)** \\ \hline Confidence in assessing PCI with ultrasound & 3.87 (1.01) & 0.005 & 0.28 \\ \hline Confidence in identifying NCI with ultrasound & 4.03 (0.98) & \textless{}0.001 & 0.40 \\ \hline Confidence in identifying MCI with ultrasound & 3.79 (1.02) & 0.002 & 0.34 \\ \hline Confidence in identifying VCI with ultrasound & 3.58 (1.03) & 0.002 & 0.35 \\ \hline Ability to spatially visualise placenta and PCI while performing ultrasound & 4.00 (1.00) & 0.17 & \\ \hline Ability to spatially visualise placenta and NCI while performing ultrasound & 4.09 (1.10) & 0.002 & 0.35 \\ \hline Ability to spatially visualise placenta and MCI while performing ultrasound & 3.84 (1.08) & 0.22 & \\ \hline Ability to spatially visualise placenta and VCI while performing ultrasound & 3.55 (1.15) & 0.007 & 0.26 \\ \hline \end{tabular}
\begin{tabular}{l l l l} \hline
**PCI: placental cord insertion. NCI: normal cord insertion, MCI: marginal cord insertion, VCI: velamentous cord insertion.**  
\end{table} 
Table 1: The mean ratings for participant confidence and ability to spatially visualise the PCI, pre-demonstration. \begin{table}
\begin{tabular}{l l l} \hline
**PCI: placental cord insertion. NCI: normal cord insertion, MCI: marginal cord insertion, VCI: velamentous cord insertion.**  
\end{table} 
Table 2: Participant confidence in assessing and spatially visualising the PCI, pre-demonstration, according to years of experience, with \(p\)-values shown. NCI, MCI, and VCI (ranked 1 in 81.8%, 78.8%, and 84.8%, respectively) and the 3 DPMs the most beneficial (ranked 3 in 69.7%, 75.8%, and 78.8%, respectively). Table 3 documents the ranking of the images, videos, and 3 DPMs for each PCI category. There was no significant association between the ranking and the participant's years of experience, df = 4.