Children that are born between the 36th and 39th week (38 and 41 weeks after the LMP) are considered as being normal deliveries. Statistically, only 2/3 of all children are born within the 3 weeks around the calculated date of birth and around 80 % within a month around the predicted date of birth.
Giving birth proceeds in three periods:
Expulsion or press period (subdivided into 4 phases)
During delivery the infantile head has to conform to the various pelvic sections. In the expulsion period the first 3 phases describe the development of the head while phase 4 that of the shoulders, whereby the head rotates 90° back again.