**Core Concept**
Chilotic lines, also known as chilotic ridges or chilotic grooves, are a series of parallel lines or ridges on the surface of the placenta. These lines are formed by the contraction and relaxation of the uterine muscles during pregnancy, which causes the placental tissue to be compressed and stretched. The formation of chilotic lines is an essential aspect of placental development and function.

**Why the Correct Answer is Right**
Chilotic lines are used to determine the age of the fetus, specifically during an autopsy or examination of a placenta. By counting the number of chilotic lines, the gestational age of the fetus can be estimated, as each line represents approximately one week of fetal development. This method is particularly useful in cases where the exact gestational age is unknown, such as in stillbirths or fetal deaths.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because chilotic lines are not used to determine the sex of the fetus. While the presence of certain sex chromosomal abnormalities may be associated with placental abnormalities, the chilotic lines themselves do not provide information on fetal sex.

**Option B:** This option is incorrect because chilotic lines are not used to determine the presence of fetal anomalies. While certain fetal anomalies may be associated with placental abnormalities, the chilotic lines themselves do not provide information on fetal anatomy or pathology.

**Option C:** This option is incorrect because chilotic lines are not used to determine the presence of maternal medical conditions. While certain maternal medical conditions may be associated with placental abnormalities, the chilotic lines themselves do not provide information on maternal health or pathology.

**Clinical Pearl / High-Yield Fact**
When examining a placenta, it is essential to note the presence and number of chilotic lines, as this information can be crucial in determining the gestational age of the fetus. This is particularly important in cases where the exact gestational age is unknown, such as in stillbirths or fetal deaths.

**Correct Answer:** D. The correct answer is D, as chilotic lines are used to determine the age of the fetus.