**Core Concept**
Shoulder presentations refer to a type of malpresentation in obstetrics where the baby's shoulder is the presenting part, often occurring in cases of multiple gestations or fetal macrosomia. The complications associated with shoulder presentations are a significant concern for both the mother and the baby.

**Why the Correct Answer is Right**
The complications of shoulder presentations can be attributed to the difficulties in navigating the pelvic inlet and outlet, leading to an increased risk of fetal distress, umbilical cord prolapse, and dystocia. The shoulder presentation can also cause a prolonged second stage of labor, resulting in maternal exhaustion and potential complications such as shoulder dystocia and birth asphyxia.

**Why Each Wrong Option is Incorrect**
**Option A:** **Fetal macrosomia** is actually a risk factor for shoulder presentations, making it a correct association rather than a complication.

**Option B:** **Umbilical cord prolapse** is indeed a complication of shoulder presentations, as the presenting part can cause the umbilical cord to prolapse, leading to fetal distress and potential complications.

**Option C:** **Dystocia** is also a correct complication of shoulder presentations, as the baby's shoulder can become impacted in the birth canal, leading to a prolonged and difficult delivery.

**Clinical Pearl / High-Yield Fact**
One key point to remember is that shoulder presentations are often associated with fetal macrosomia, and these cases require close monitoring and careful management to prevent complications.

**Correct Answer:** D.