Thursday, April 23, 2009



What is labor?

Picture: Cardinal movements of labor: A.Engagement; B.flexion;C.descent and internal rotation; D. and E. extension; F. external rotation
Source: F.John Bourgeois et al. Obstetrics and Gynecology Recall, Philadelphia, 2008, p 62

Labor is the process by which the products of conception are normally delivered. Regular uterine contraction that cause progressive effacement and dilatation of the cervix and lead to expulsion of the fetus and placenta from the uterus.
What is effacement?
Effacement is shortening of the cervix and thinning the cervical wall caused by the pressure of the fetus’s head as it descend into the birth canal during labor.
What are the stages of normal labor?
1.The first stage is the period from the onset of labor contraction to full dilatation of the cervix; this stage ends with complete [10 cm] dilatation of the cervix. This stage is by far the longest. The average duration of the first stage is about 15 hours for the primigravidas and about 8 hours for the multiparas. However the first stage of labor may be less than one hour or more than 24 hours.
What conditions may slow progress in the active phase of labor?
Uterine dysfunction, fetal mal-position, cephalo-pelvic disproportion [CPD]
2.The second stage is the period from the full dilatation of cervix to the delivery of the fetus.. The second stage duration of primigravidas is about 30 minutes to 2 hours; multiparas varies from a few minutes to 45 minutes [average].
Spontaneous delivery of the fetus presenting by the vertex is divided into 3 phase:
· Delivery of the head;
· Delivery of the shoulders;
· Delivery of the body and legs.
What are the mechanisms or cardinal movement of labor ?
Engagement: Generally occurs in late pregnancy or onset of labor.
Flexion of fetal neck toward chest, good flexion is noted in majority of cases.
Descent is usually slowly progressive, depends on pelvic architecture relationships.
Internal rotation takes place during descent. Vertex usually rotates to the transverse. It next rotate to the anterior or posterior to pass the ischial spines, whereupon, when vertex reaches the perineum, rotation from a posterior position usually follows.
Extension: Follows distention of perineum by vertex. Head concomitantly stems beneath the symphysis [pubic arch]. Extension is complete with delivery of the head.
External rotation or restitution: Following delivery, head normally rotates to the position it originally occupied at engagement. Next the shoulders descend [in a path similar to that traced by the head]. They rotate anterior-posteriorly for delivery. Then the body and the legs of the baby is delivery next.
3.The third stage of labor
or placental stage is the period from the birth of the infant to
the delivery of the placenta, including recovery of the placenta and the hour
How long does the third stage of labor last? It is about 30 minutes.
What are the stages of placental delivery? Separation of the placenta from the uterine
wall. Expulsion from the vagina.
Why is the placenta examined after delivery? To ascertain its complete removal from the uterine cavity
How is uterine hemostasis achieved after delivery of the placenta? Vasoconstriction by myometria contraction.
How can uterine contractions after delivery of the placenta be stimulated? Agents such as Oxytocin [generic, Pitocin]10 units/ml for IM injection and uterine massage.
What type of lacerations may require repair?
· First-degree laceration involves the vaginal mucosa or perineal skin.
· Second-degree laceration extends into the sub-mucosal tissue of the vagina or perineum with or without involvement of the muscles of the perineal body.
· Third-degree laceration involves the anal sphincter.
· Fourth-degree laceration involves the rectal mucosa.

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