## 4 Discussion  
Comprehensive understanding of complex anatomy can be challenging in all aspects of medical imaging. Imaging modalities primarily produce 2D images, which limits the spatial perception of anatomical relationships [28]. Studies have demonstrated medical students find visualising anatomy in three dimensions particularly challenging [29]. Even when 3D imaging is undertaken, interpreting 3D images on flat 2D screens can impede understanding of complicated anatomy [28; 30; 31]. The production of 3 DPMs can bypass this problem by providing clear visualisation of spatial relationships [5]. [PERSON] et al. stated that despite the availability of excellent 2D resources, visualising anatomical spatial relationships remains challenging [4]. This suggests 2D resources on their own may not be adequate for teaching anatomy, one of the most onerous subjects for students due to the need for spatial visualisation [32]. [PERSON] et al. suggested the use of 3D models would improve a student's understanding of a 2D ultrasound image resulting in increased confidence in recognising anatomy [33]. In our study, participants indicated the 3 DPMs were more beneficial in terms of visualising the NCI, MCI, and VCI than the more traditional methods of 2D ultrasound images and videos. Our findings concur with the \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Opinions** & **Mean** & **SD** & _p-Value_ \\ \hline Do you think the 3D model of the NCI would be useful in ultrasound education? & 4.55 & 0.97 & 0.605 \\ \hline Do you think the 3D model of the MCI would be useful in ultrasound education? & 4.73 & 0.72 & 0.601 \\ \hline Do you think the 3D model of the VCI would be useful in ultrasound education? & 4.97 & 0.17 & 1.000 \\ \hline Would you recommend the 3D model of the NCI as an educational device? & 4.42 & 1.09 & 0.582 \\ \hline Would you recommend the 3D model of the MCI as an educational device? & 4.54 & 0.83 & 0.930 \\ \hline Would you recommend the 3D model of the VCI as an educational device? & 4.81 & 0.39 & 0.622 \\ \hline \hline \end{tabular}  
3D: three-dimensional, NCI normal cord insertion, MCI: marginal cord insertion, VCI: velamentous cord insertion.  
\end{table} 
Table 6: Mean ratings of the usefulness of 3 DPMs in ultrasound education based on participants’ opinions, n = 33. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Theme** & **Feedback** & **Total** \\ \hline Use of 3 DPMs of the PCI as & Useful teaching resources for trainees and junior staff (n = 4) & n = 6 \\ educational tools & Useful educational tool to explain different types of PCI (n = 2) & n = 8 \\ \hline Improved visualisation of the PCI & Better visualisation and understanding of PCI (n = 6) & n = 8 \\ \hline Extended use of the 3D models & The 3D models could help spatially visualise placental location (n = 1) & n = 2 \\  & and placental developmental variations (n = 1) & n = 2 \\ \hline General comments & Could be helpful in explaining our images/videos of the PCI to radiologist (n = 1) & n = 3 \\  & Excellent for dyslexic students who require a more visual approach to study (n = 1) & n = 3 \\  & The videos and 3D models pair nicely together (n = 1) & n = 1 \\ \hline Limitations & Cost and availability (n = 1) & n = 1 \\ \hline \hline \end{tabular}  
3 DPMs: three-dimensional-printed models, PCI: placental cord insertion, VCI: velamentous cord insertion, 3D: three-dimensional.  
\end{table} 
Table 7: Thematic analysis of qualitative data. literature that 3 DPMs increase spatial visual orientation [34] and assist with understanding anatomical relationships [35]. 3 DPMs are being progressively valued in ultrasound education with their ability to accurately depict anatomical structures [17; 36] and provide both a visual and tactile representation which improves understanding, particularly of complex anatomy [7; 19].