You are assisting in a delivery of a 41-week, 3-day gestation infant being born to a mother with gestational diabetes. The head delivers normally, but then seems to retract partway back into the birth canal. Which condition should you suspect?

If during the vaginal cephalic delivery, there is a requirement of additional obstetric maneuvers after the head of the fetus has been delivered however the gentle traction is failed then this condition is known as shoulder dystocia.
Shoulder dystocia occurs when the shoulder of the baby gets stuck in the pubic bone of the mother after the head has been delivered due to which the baby retracts his head back into the birth canal.
Gestational diabetes is one of the conditions that impose a risk on the baby to have shoulder dystocia during the delivery.
Since in the given question it is mentioned that the mother has gestational diabetes and the head has been delivered but seems to retract back, this points out that the condition suspected is shoulder dystocia.

You are assisting in a delivery of a​ 41-week, 3-day gestation infant being born to a mother with gestational diabetes. The head delivers​ normally, but then seems to retract partway back into the birth canal. Which condition should you​ suspect?