Normal labor and delivery Flashcards
Function of uterine contractions
dilate the cervix and to push the fetus through the birth canal
Fetus’ ability to successfully negotiate the pelvis is dependent upon the complex interaction of three mechanical variables, known as the “three Ps”
the powers, the passenger, and the passage
the force generated by the uterine musculature during contractions
the powers
the occurence of how many contractions in 10 minutes defines adequate labor
three to five contractions
the long axis of the fetus relative to the longitudinal axis of the uterus. can be longitudinal, transverse, or oblique
fetal lie
degree of descent of the leading edge of the presenting part of the fetus, typically measured as distance in centimeters between the leading bony edge of the fetus and the ischial spines
station
What has replaced pelvimetry?
clinical trial of the pelvis (trial of labor)
refers to the interval between the onset of labor and full cervical dilatation. divided into two phases
first stage of labor
period between the onset of labor and the point at which a change in the slope of the rate of cervical dilatation is noted. It is characterized by slow cervical dilatation, and is of variable duration
latent phase (of 1st stage)
associated with a faster rate of cervical dilatation and usually begins by 2 to 4 cm of cervical dilatation
active phase (of the 1st phase)
minimal rate of cervical dilation for nulliparous and multiparous woman
- 2 cm per hour for a nulliparous patient
- 5 cm per hour fo a multiparous patient
*note these values are 2 standard deviations below the mean
Average duration of the first stage of labor without anesthesis for nulliparous and multiparous patients
16.5 hr for nulliparous and 12.5 for multiparous
*note anesthesia increases duration of labor ~2hrs
refers to the interval between full cervical dilatation (10 cm) and delivery of the infant. It is characterized by descent of the presenting part through the maternal pelvis and culminates with expulsion of the fetus
2nd stage of labor
refers to the time from delivery of the baby to separation and expulsion of the placenta
3rd stage
The major complication associated with 3rd stage of labor
hemorrhage
commonly used endpoint for intervention in the absence of complications (eg, hemorrhage) during the 3rd stage of labor
Retention of the placenta for longer than 30 minutes at term
refers to the passage of the widest diameter of the presenting part to a level below the plane of the pelvic inlet. In the cephalic presentation with a well-flexed head, the largest transverse diameter of the fetal head is the biparietal diameter (9.5 cm)
engagement
refers to the downward passage of the presenting part through the pelvis.
descent
occurs passively as the head descends due to resistance related to the shape of the bony pelvis and by the soft tissues of the pelvic floor
flexion
the rotation of the presenting part from its original position (usually transverse with regard to the birth canal) to the anteroposterior position as it passes through the pelvis
internal rotation
occurs once the fetus has descended to the level of the introitus. This descent brings the base of the occiput into contact with the inferior margin of the symphysis pubis
extension
After the fetal head deflexes (extends), it rotates to the correct anatomic position in relation to the fetal torso; left or right rotation depends on the orientation of the fetus
external rotation
refers to delivery of the body of the fetus. After delivery of the head and external rotation, further descent brings the anterior shoulder to the level of the symphysis pubis. The anterior shoulder rotates under the symphysis pubis
expulsion
