Extensive observational research in the obstetric population has demonstrated that airway changes, including increasing MMS and decreasing oropharyngeal volume, occur during labor. It has been found that 63% of parturients experienced an increase in MMS over the course of their labor, with the fraction of patients scoring 3 or 4 peaking at 51.7%, compared with only 10.3% early in labor. Notably, of those patients that reached a class 4, 21% remained at that classification 48 hours postpartum. It has been found that 18% of patients whose airway class worsened during labor had not returned to their prelabor class 36-48 hours after delivery.