Generally, the onset of labor begins with uterine contractions that bring about cervical effacement and dilation (thinning and opening). One of the most common indications of true labor used in hospitals in the United States and developed countries is dilation between 3 and 4 centimeters accompanied by regular contractions.
Today, women are examined in the hospital or clinic to verify active labor. Timely, accurate measurement of cervical dilation is critical as it determines the different stages of active labor and can be one important indicator of abnormalities.
Women are subjected to numerous manual vaginal examinations (in many cases, performed by different members of the labor and delivery team) to measure cervical dilation and effacement. These examinations rely on some level of subjectivity by the examiner, so results may vary or may be inaccurate depending on the clinician.
Moreover, many women arrive at the hospital either to wait around for hours or to be sent home due to false labor.