Normal and abnormal labor

Question 1

Components of labor 1

Answer 1

• 3 Ps: power, passenger (baby) and pelvis
• Power: force of uterine contractions (frequency, duration, amplitude) measured directly in montevideo units by intrauterine pressure catheter (IUPC)
• Montevideo units: avg amplitude of contractions x number of contractions in 10 min
• Passenger: fetal size (most concerned about large fetus- macrosomia), lie (position of fetus), presentation (cephalic, breech, or shoulder), attitude (degree of fetal head flexion), position (of fetal occipital area), and station (where the fetus is in descent
• Lie: longitudinal axis of fetus relative to mother’s spine
• Nl lie is longitudinal, other forms are transverse or oblique

Question 2

Components of labor 2

Answer 2

• Nl presentation is cephalic (head first), abnormal ones are breech (butt first), or shoulder
• Nl attitude and position: occipital bone should be coming out first and should be facing toward mother’s sacrum (suboccipitobregmatic)
• Station: measure of where the fetus is relative to ischial spine (spine = 0, -1 is inward and +1 is outward)
• 3rd P (pelvis): shape of pelvis (nl is gyenecoid), measurements of pelvic inlet, mid pelvis, pelvic outlet
• Best predictor of successful vaginal birth is Hx of previous vaginal birth

Question 3

Labor definition

Answer 3

• Uterine contractions that result in cervical change
• False labor (braxton-hicks contractions): uterine contractions no associated w/ cervical change (shorter duration, less intense, irregular)
• Cervical insufficiency (bad): cervical dilation w/o contractions

Question 4

3 stages of labor

Answer 4

• 1: onset of labor until complete cervical dilation (10cm)
• 2 phases to first stage: latent and active
• Latent phase: early labor, transition to active phase is 5-6cm dilation (time to active phase highly variable)
• Active phase: greater rate of cervical dilation
• Both phases are longer in women who are nullipara (btwn 7-11 hrs total)
• 2: complete cervical dilation (starts at 10cm) to expulsion of fetus (pushing phase)
• 2nd stage relatively short (20 min - 1 hr)
• 3: expulsion of fetus to expulsion of placenta (usually under 5 min, abnormal if more than 30 min)

Question 5

Rx for abnormal labor

Answer 5

• Protracted latent phase (too long) can be Rx w/ pitocin (synthetic oxytocin) for labor augmentation
• Protracted active phase (dilation rate <1.2 cm/hr or 1.5cm/hr in multipara): amniotomy (break the membranes containing amniotic fluid), monitor contraction strength, pitocin
• Arrest of active phase: cannot be diagnosed until ≥6cm dilated, characterized by no cervical change for 4 hrs (w/ contractions and ruptured membranes) or 6 hrs (inadequate contractions and ruptured membranes)
• Rx is amniotomy, pitocin, cesarean delivery
• Protracted second stage (epidural will slow second stage by slowing pushing, but does not slow down labor): piton, amniotomy, positional changes, support, operative vaginal delivery (vacuum extraction or forceps delivery), C section