Prelabor contractions are called Braxton-Hicks contractions. While they don’t bring about dilation of the cervix, these practice contractions help to ripen, efface, and move the cervix forward. You will likely sense a tightening or pressure that lasts for 30 to 40 seconds, coming every 10 to 20 minutes. Typically, prelabor will last for less than a day. Some women will experience a longer-than-average prelabor. It’s considered prolonged if it lasts for longer than 24 hours.