**Core Concept**
Intracranial hemorrhage is a significant cause of perinatal mortality in term frank breech presentations due to the potential for fetal head compression and vascular injury during delivery.

**Why the Correct Answer is Right**
In frank breech presentations, the fetus's head is compressed against the maternal pelvis, which can lead to increased intracranial pressure and subsequent hemorrhage. This is particularly concerning in term pregnancies, where the fetal brain is fully developed and more susceptible to injury. The compression of the head can cause damage to the bridging veins that drain blood from the brain, resulting in hemorrhage. The risk of intracranial hemorrhage is higher in frank breech presentations compared to other types of breech presentations, such as footling breech.

**Why Each Wrong Option is Incorrect**
**Option A:** Delay in delivery of head is not the chief cause of perinatal mortality in term frank breech presentation. While a delay in delivery can contribute to fetal distress, it is not the primary factor in intracranial hemorrhage.

**Option B:** Prolapse of umbilical cord is a potential complication in breech presentations, but it is not the chief cause of perinatal mortality in term frank breech presentation. Prolapse of the umbilical cord can lead to fetal distress and compromise, but it is not directly related to intracranial hemorrhage.

**Option D:** Abnormalities are not the chief cause of perinatal mortality in term frank breech presentation. While fetal abnormalities can contribute to perinatal mortality, they are not directly related to the specific risks associated with frank breech presentations.

**Clinical Pearl / High-Yield Fact**
In term frank breech presentations, it is essential to consider the risk of intracranial hemorrhage and expedite delivery to minimize the risk of fetal injury. A careful evaluation of fetal well-being and a plan for prompt delivery are crucial in managing these cases.

**✓ Correct Answer: A. Intracranial hemorrhage**