Final answer:
The maternal anatomic landmark used for determining fetal station during labor is the ischial spine.
Step-by-step explanation:
The question being asked relates to the anatomic landmarks used in the obstetrical assessment of the fetal station during labor. The fetal station is a measure of how far the baby has descended into the pelvis and is determined in relation to a specific anatomic landmark on the mother's pelvis.
The maternal anatomic landmark that serves as the baseline for the determination of fetal station is the ischial spine. The ischial spines are part of the bony structure of the pelvis and are located approximately midway between the maternal symphysis pubis and the sacral promontory. When the presenting part of the fetus is at the same level as the ischial spines, the fetal station is said to be 0. If the presenting part is above the spines, it is measured in negative numbers, and if it is below, in positive numbers.