Final answer:
The most appropriate next step in management of this patient, who is displaying signs of shoulder dystocia during labor, is to apply suprapubic pressure to dislodge the infant's shoulder.
Step-by-step explanation:
The situation described is indicative of a shoulder dystocia, where the baby's head is delivered but the shoulders are stuck behind the mother's pelvic bone. The retraction of the head towards the pelvis, often called the 'turtle sign,' is a classic signal of this complication. Given the urgency to relieve the dystocia to prevent fetal hypoxia and potential brachial plexus or clavicle injuries, the most appropriate next step in management of this patient is D. Suprapubic pressure.
This technique involves applying pressure just above the maternal pubic bone in order to dislodge the infant's anterior shoulder from behind the pubic symphysis. Other options like fundal pressure are contraindicated because they can worsen the impaction and increase the risk of uterine rupture. Fracturing the baby’s clavicles is an extreme measure that is rarely used. A Caesarean section cannot be performed because the head is already delivered, and oxytocin is not indicated as it does not resolve the shoulder dystocia and can intensify contractions potentially causing further complications.