**Core Concept:** Ratio of fresh placental weight to infant weight in the last trimester of pregnancy is an important parameter to evaluate placental function. A healthy placenta is essential for a healthy pregnancy outcome.

**Why the Correct Answer is Right:** The correct answer, D, is derived from the concept of placental efficiency, which is a measure of how well the placenta is functioning. A healthy placenta provides adequate oxygen, nutrients, and waste removal for the growing fetus. The ratio of fresh placental weight to infant weight represents the efficiency of placental function. This ratio is usually around 10-12 grams per kilogram of infant weight.

**Why Each Wrong Option is Incorrect:**

A. Placental weight and infant weight are directly proportional. This option contradicts the concept of placental efficiency and is incorrect.
B. This option discusses the importance of placenta and infant growth, but does not provide the correct ratio.
C. This option talks about placental weight and fetal weight but provides an incorrect ratio.

**Clinical Pearl / High-Yield Fact:**

A reduced placental efficiency can lead to intrauterine growth restriction (IUGR), which is a significant risk factor for perinatal morbidity and mortality. Monitoring the placental efficiency ratio can help identify potential complications early in pregnancy, allowing for timely interventions.

**Correct Answer:** D. The correct ratio of fresh placental weight to infant weight in the last trimester of pregnancy is around 10-12 grams per kilogram of infant weight. Assessing this ratio can help evaluate placental function and identify potential complications, such as intrauterine growth restriction (IUGR).