At what cervical dilation and station does posterior arrest generally occur?

Posterior arrest typically occurs during labor when the baby is in a position that is less favorable for descent through the birth canal, often related to the station of the fetal head and the degree of cervical dilation.

When considering the correct answer, cervical dilation of 6 cm paired with a station of -3 or -2 indicates that the fetal head is still relatively high in the pelvis and not yet engaged in the birth canal. At this point, the labor may stall or progress very slowly because the position can impede effective contractions from moving the baby down, which is a scenario frequently described in cases of obstructed or stalled labor.

Labor dynamics are heavily influenced by the baby's positioning; a head that is not engaged (at stations lower than -1) can lead to prolonged labor. This combination reflects a common scenario where the cervix is not fully dilated, but the baby has not descended adequately, resulting in an arrest of descent. Understanding this allows healthcare providers to assess labor progress and make decisions about potential interventions that may be necessary to assist the mother and child.