Life in the Womb - Normal Labor and Delivery

Parturition is the birth process of the baby. Labor begins with involuntary uterine contractions that first result in effacement and dilation of the cervix, and then, in conjunction with voluntary bearing-down of the mother, the progress of the baby down the birth canal. Crowning is the presentation of the baby's head at the introitus or vaginal opening. Delivery occurs with the complete birth of the baby!

Five essential factors influence the process of labor: the baby or the passenger, the size of the birth canal, or "passageway," the "power" or strength, frequency, and duration of uterine contractions, the position of the placenta, and the psychologic state of the mother.



Vertex and Breech Presentations

The ideal situation is for the baby to be in a longitudinal or vertical lie and to present head first in the birth canal, or vertex presentation. Delivery may be difficult if the baby is in a vertical lie but a breech presentation. Breech presentations are called frank when the pelvic sacrum enters first, complete when the pelvis and both feet enter, and footling when one foot enters the birth canal. Delivery is impossible if the baby is in transverse lie, and this generally leads the obstetrician to surgically remove the baby by Caesarean Section.

There are three traditional stages to labor.


The first stage occurs from the beginning of uterine contractions to the complete dilatation of the cervix. The beginning of labor often coincides with "show," the discharge of the mucus plug of the cervix, and the "water breaking," the release of amniotic fluid with the rupture of the amniotic sac. Effacement of the cervix means the thinning of the cervix, and dilatation refers to the widening of the cervical diameter from 1 cm to 10 cm, to allow for the progress of the baby down the birth canal.



The second stage lasts from full dilatation of the cervix with transition down the birth canal, to the actual delivery of the baby. Progress in the descent of the presenting part (usually the head) is determined by vaginal examination until crowning occurs. The location of the head in relation to the ischial spines is designated the station, and is a mean of determining the progress of the baby down the birth canal. The level of the ischial spines is considered to be station 0, and the position of the head is described in centimeters minus (-1 to -5) above the spines or plus (+1 to +5) below the spines.




Delivery of the Infant



Once crowning (A) occurs, gentle delivery of the head (B) follows. Gentle downward traction brings descent and then delivery of the anterior shoulder (C). Subsequent gentle upward traction allows delivery of the posterior shoulder (D). The rest of the body easily follows once the shoulders are delivered, and the newborn is here!
The baby enters the world of relationship!

The third stage occurs from the delivery of the baby to the delivery of the placenta.