"cm dilation" refers to the measurement of the opening of the cervix during childbirth. It indicates how much the cervix has widened in centimeters to allow the baby to pass through the birth canal. Full definition
Healthy women who go into labor on their own should not be expected to progress at a rate of 1 cm dilation per hour in the first stage of labor and therefore need no interventions to speed up their labor. (vbac.com)
Physically, the cervix is beginning to efface and dilate and this stage lasts until the Mother reaches 4 to 5 cm dilation. (thematrona.com)
In conventional terms, the Mother has achieved 4 or 5 cm dilation and the character of the labor changes. (thematrona.com)