**Core Concept**
The question pertains to the obstetric application of forceps in childbirth, specifically the structure held by forceps during delivery. The correct answer requires an understanding of the anatomy and obstetric techniques involved. The forceps used in obstetrics are designed to facilitate a safer and more controlled delivery by reducing the risk of complications.

**Why the Correct Answer is Right**
The structure held by forceps during delivery is the fetal head. The forceps are placed on the fetal head to facilitate its downward movement through the birth canal, thereby reducing the risk of complications such as fetal distress or injury to the mother. The forceps are typically applied to the fetal head in a specific manner, taking into account the position of the head and the size of the birth canal. The use of forceps requires great skill and precision to avoid injury to both the mother and the baby.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the fetal body is not typically held by forceps during delivery. While forceps may be used to help guide the fetal body through the birth canal in certain situations, they are not designed to hold the entire body.
**Option B:** This option is incorrect because the placenta is not held by forceps during delivery. The placenta is typically delivered after the baby, and forceps are not used to facilitate its delivery.
**Option C:** This option is incorrect because the umbilical cord is not held by forceps during delivery. The umbilical cord is typically clamped and cut after the baby is delivered, and forceps are not used to hold it.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the correct application and use of forceps in obstetrics require great skill and precision to avoid complications. Obstetricians must carefully assess the situation and consider the risks and benefits of using forceps before making a decision.

**Correct Answer: D. Fetal head.**