Increased BMI at booking was associated with a reduced incidence of minor perineal trauma at delivery, but was not associated with OASIS.

In our study, instrumental deliveries, the use of internal manoeuvres (Woods' screw and reverse Woods' screw) and four or more manoeuvres for the management of SD were independently associated with a higher incidence of OASIS. To effectively manage shoulder dystocia with lower risks of perineal trauma, these factors could be considered when designing further prospective studies and developing management protocols.

Measurements of six POP-Q points obtained with traction showed a higher grade of POP than those assessed with Valsalva maneuver. On this basis, surgeons might decide on the extent of surgical procedure after examination under anesthesia; however, preoperative patient counselling would be essential to obtain consent for this approach. The clinical significance of the findings requires further evaluation.

To our knowledge, this is the first preliminary study to evaluate the role of MRI-based 3D pelvic models for investigating paraurethral masses. This is a feasible technique and may prove a useful addition to conventional 2D MRI. Further prospective studies are required to evaluate this modality for investigating such lesions and planning appropriate management.

The incidence of third- and fourth-degree tears following rotational Kielland's forceps delivery and other non-rotational forceps deliveries is comparable.