Which intervention may cause further impaction of the fetal shoulder in a delivery with shoulder dystocia?

Fundal pressure is known to potentially worsen shoulder dystocia during delivery. This is because applying pressure to the fundus may inadvertently push the fetal shoulders down against the pelvic brim instead of helping to relieve the obstruction. The maneuver can cause the fetal shoulders to become more firmly impacted behind the pubic symphysis, making the situation worse rather than providing the necessary relief for the baby.

In contrast, other interventions such as the Gaskin maneuver and the McRoberts maneuver are specifically designed to help relieve shoulder dystocia. The Gaskin maneuver involves having the mother get on all fours, which can help to create more room in the pelvis and allow the shoulders to rotate and descend more effectively. The McRoberts maneuver involves flexing the mother's thighs up towards her abdomen, which also opens the pelvis and can help to realign the fetal shoulders. Suprapubic pressure, applied in a specific manner, can help to nudge the fetal shoulder out of the impacted position without causing further issues.

Thus, while fundal pressure may lead to additional complications in cases of shoulder dystocia, the other maneuvers are known to be effective interventions in alleviating the situation.