Dysfunctional Labor, Uterine Contractility and Dystocia Flashcards
uterine relaxation
-maintained by factors that inc cAMP
uterine contraction
- inc intracellular ca stores
- promote interaction of actin and myosin causing uterine contractions
during labor- 2 segments of uterus are formed
- upper- contracts and retracts to expel fetus
- lower- becomes thinner and passive
physiologic changes of labor- cervix
- contains collagen and smooth m
- changes from firm, intact sphincter to soft, pliable, dilatable
- due to collagenolysis, inc in hyaluronic acid, dec in dermatan sulfate- favors inc water content
stages of labor
(labor- regular uterine contractions to bring about effacement and dilation of cervix)
- 1st- onset of contractions to full dilation of cervix
- 2nd- full dilation of cervix to delivery of infant
- 3rd- delivery of infant to delivery of placenta
1st stage of labor
- Latent phase- cervical softening and effacement occurs with minimal dilation (<4 cm)
- Active phase- starts when cervix is dilated to 4 cm
- inc rate of cervical dilation
- descent of presenting fetal part
- acceleration phase
- deceleration phase
for all phases of labor, the abnormality may be either
- protraction- slower than normal rate
- arrest- complete cessation of progress
latent phase- normal time
- nulliparous- up to 20 hrs
- multiparous- up to 14 hrs
prolonged latent phase- etiology
- those who have entered labor w/o substantial cervical change
- excessive use of sedatives or analgesics
- fetal malposition
prolonged latent phase- management
therapeutic rest (sleep) -morphine (80% will progress to active phase; 15% will stop having contractions- false labor)
Active phase- normal time limits
- nulliparous- cervical dilation of 1.2 cm/h
- multiparous- 1.5 cm/h
active phase- abnormalities
- protraction- if cervical dilation rate is <
- arrest- 2 or more h’s with no cervical dilation
fetal descent- normal time
- nulliparous- 1 cm/h
- multiparous- 2 cm/h
- protraction- <
- arrest- no change in 1 h
active phase abnormalities- etiology
- inadequate uterine activity
- cephalopelvic disproportion
- fetal malposition
- anesthesia
- can have inc risk of perinatal mortality
Dystocia
“difficult labor”/ dysfxnal labor (labor not progressing normally)
- abnormalities of the 3 P’s:
- Power (uterine contractions, maternal expulsive forces)
- Passenger (position, size, presentation of fetus)
- Passage (maternal pelvic bone contractures)
- dx should NOT be made b/f an adequate trial of labor has been tried
active phase abnormalities- management
-augmentation
Augmentation
- stim of uterine contraction (when spontaneous contractions have failed to result in progressive dilation or descent of fetus)
- consider if contractions < 3 in 10 min or intensity < 25
- oxytocin- after assessing maternal pelvic, fetal position, station, maternal and fetal status
active phase abnormalities- Power
IUPC (intrauterine pressure catheter)- measures intensity
- requires membranes to be ruptured
- benefits- augment labor, allows assessment of meconium status
- risks- cord prolapse, prolonged rupture assoc with chorioamnionitis
Assessing Power- minimal effective uterine activity is what?
- 3 contractions in 10 min, averaging 25 above baseline
- MVU (montevideo units)- measures peaks of contraction in 10 min- >200 MVU for 2 hrs
- b/f proceeding to c-section- document adequate contractions for 4 hrs
Inadequate uterine contractions- start what med?
Pitocin!!
- stim uterine contractions- inc intracellular ca
- 20-30 min needed for full effect
- 80% of pts w/ a disorder of labor will respond!
active phase abnormalities- Passage
CPD (cephalopelvic disproportion)
- inc likelihood in nulliparous women who present in labor with an unengaged head
- gynecoid and anthropoid pelvic- good prognosis for delivery!
- pubic arch > 90
- ischial tuberosity > 8.5 cm
- diagonal conjugate > 11.5
- prominence of ischial spines
active phase abnormalities- Passenger
- presentations other than vertex OA are abnormal
- fetal head usually enters the maternal pelvic in OT position- then rotates to OA
- can persist in OT position or rotate to OP
- also caused by: macrosomia, shoulder dystocia, fetal anomalies
Persistent OT Position
- head fails to rotate and flex into OA position
- caused by cephalopelvic distortion, altered pelvic architecture, relaxed pelvic floor (epidural)
- transverse arrest of descent- persistent OT position with arrest of descent for 1 hr
- arrest occurs b/c of the deflexion that occurs with OT positions- occipitofrontal diameter (11cm) becomes the presenting diameter
Persistent OT position- management
- if pelvis is adequate, infant is not macrosomic, and contractions are inadequate: start oxytocin, rotation (manually or kielland forceps)
- if pelvis is inadequate or infant is macrosomic- c-section
Persistent OP position
- some heads rotate to OP initially, and then rotate during labor to OA (5-15% persist in OP position)
- course of labor in OP position usually normal
- 2nd stage may be prolonged
- more back discomfort
Persistent OP position- management
- observation of prolonged 2nd stage of labor is appropriate
- delivery of head often occurs spontaneously
- operative vaginal delivery (vacuum or forceps)
Macrosomia
- macrosomia- fetus weighs 4500 g
- LGA- wt > 90% for a given gestational age
- dx of macrosomia- Us!!
Passenger- developmental abnormalities
- hydrocephalus- can cause enlargement of head
- fetal ascites or enlargement of fetal organs- enlarged fetal abdomen- immune hydrops (Rh isoimmunization!!), nonimmune hydrops (infections, chromosomal abnormalities)
- conjoined twins, locked twins
Abnormalities of Active Phase- after assessing the 3 P’s
may proceed to C-section if indicated
risk factors for macrosomia
- maternal diabetes
- prev hx
- maternal obesity
- wt gain during pregnancy
- multiparity
- male fetus
- gestational age > 40 wks
- ethnicity
- maternal < 17 yo
- 50-g glucose screen w/ a neg result on 3 h
macrosomia- risks
- maternal morbidity- inc risk for c-section; postpartum hemorrhage, vaginal lacerations
- fetal- shoulder dystocia, fracture of clavicle, damage to n’s of brachial plexus- Erb-Duschenne paralysis (C5-6)
Brachial plexus injury
- Erb-Duschenne- upper arm palsy- most common- C5-6
- Klumpke- lower arm palsy- C8, T1
- paralysis of entire arm- damage to all 4 n roots
Macrosomia- c-section when?
- > 5000 g in non diabetic pts
- >4500 g in diabetic pts
shoulder dystocia
- delivery that requires additional maneuvers following failure of gentle downward traction on fetal head to effect delivery of shoulders
- caused by impaction of ant fetal shoulder behind maternal pubic symphysis or impaction of post shoulder on sacral promontory
- turtle sign- retraction of delivered head against maternal perineum
shoulder dystocia- neonatal risks
- brachial plexus injury (<10% result in permanent disability)
- fractured humerus or clavicle
- hypoxic-ischemic encephalopathy
- death
Shoulder dystocia- management
- McRobert’s maneuver!!!!- hyperflexion and abduction of maternal hips
- suprapubic pressure!!!!
- rotational maneuvers, delivery of post fetal arm, fracturing fetal clavicle
- proctoepisiotomy
- Zavanelli maneuver- last resort- cephalic replacement
Shoulder dystocia- rotational maneuvers
- Rubin- put pressure on accessible shoulder to push it twd anterior chest wall of fetus
- Wood’s corkscrew- pressure behind post to rotate the infant and dislodge theant shoulder
Shoulder dystocia- Zavanelli
- last resort
- fetal head is manually returned to prostitution position
- delivery- emergent c-section
shoulder dystocia- tx
- obstetric emergency!!
- initial maneuvers- McRoberts and suprapubic pressure
