Which of the following indicates that the fetal head is progressively visible at the vaginal introitus?

The indication that the fetal head is progressively visible at the vaginal introitus is represented by perineal bulging. As the fetus descends and the head begins to engage in the birth canal, changes in the perineal area occur as a result of the pressure being exerted by the presenting part of the fetus. Perineal bulging is a physical manifestation of this descent, reflecting that the fetal head is coming closer to emergence from the birth canal.

Loss of appetite, decreased contractions, and increased fetal movement do not relate specifically to the visibility of the fetal head at the vaginal introitus. Loss of appetite may arise due to various factors during labor but does not indicate physical changes related to delivery. Decreased contractions usually point toward labor not progressing or slowing down rather than indicating that the fetal head is visibly descending. Increased fetal movement is generally more relevant to fetal well-being in utero and does not provide information about the position or visibility of the head in relation to the introitus. Thus, perineal bulging is the most accurate indicator of the fetal head's visibility as labor progresses.