This takes time. As you move closer to the birth, your contractions will get closer together, coming every few of minutes. They may start 24 hours or more beforehand, but the cervix usually takes around eight hours to dilate sufficiently for a first baby, generally speaking, between five and 15 hours. If you go to the hospital before you’re more than 3 or 4cm dilated, you will probably be sent home again. If you’ve already been in labour for a long time, you may be injected with hormones to speed things up a little. 3 - 4cm dilation marks the beginning of the active stage of labour.