Labor & Delivery Flashcards
What are braxton hicks contractions?
also known as false labor, they are contractions not associated with dilation of the cervix
How can braxton hicks contractions be differentiated from true labor?
- they are typically shorter in duration and less intense with discomfort being characterized as over the lower abdomen and groin areas
- they are often resolved with ambulation, hydration, or analgesia
- by contrast, true labor is associated with contractions that are longer in duration, more intense, felt over the fundus with radiation of discomfort to the low back and lower abdomen, and become increasingly intense and frequent with time
What is “lightening”?
changes experienced by the patient which result from the fetal head descending into the pelvis late in pregnancy
- the lower abdomen becomes more prominent
- urinary frequency is exacerbated
- breathing is easier
- the baby feels lighter
What is a “bloody show”?
the passage of blood-tinged mucus late in pregnancy as the cervix begins effacement with concomitant extrusion of mucus from the endocervical glands
What do the terms “lie,” “presentation,” and “position”? mean with regards to labor?
- lie is the relation of the long axis of the fetus to the maternal long axis (longitudinal, transverse, or oblique)
- presentation is the present part (cephalic or breech)
- position is the relation of the fetal presenting part to the right or left side of the maternal pelvis
What is a vertex presentation?
a specific type of cephalic presentation in which the head is sharply flexed onto the fetal chest
What is the purpose of the four leopold maneuvers?
- determining what occupies the fundus, either the head or breech
- determining the location of small parts, either the spine or the limbs
- identifying descent of the presenting part
- identifying the cephalic prominence
Give three reasons to avoid vaginal examination in a women being evaluated for labor?
- premature ROM
- placenta previa
- vaginal bleeding
What is effacement and what terminology is used to describe it?
it is the shortening of the cervical canal from about 2 cm to nearly nothing, expressed as a percent of thinning from a perceived uneffaced state
Why is it significant if on a vaginal exam, a laboring woman has a cervix that is palpable more anteriorly in the vagina?
it suggests the presenting part has descended into the pelvis and means it is more likely than a posterior cervix to undergo change soon
What is pelvic station and how is it communicated?
- it is the level of the presenting part in relation to the ischial spines, which are located halfway between the pelvic inlet and pelvic outlet
- the spines are said to be zero station with each centimeter above being a negative station and each below a positive station (plus or minus 5)
Pelvic station is based on what anatomic landmark?
the ischial spines, located halfway between the pelvic inlet and pelvic outlet
What is the clinical significance of zero station?
when the presenting part of the fetus is at zero station, it suggests that the biparietal diameter of the head, the widest part, has successfully negotiated the pelvic inlet
What anatomic landmarks define the pelvic inlet?
the sacral promontory and symphysis pubis
What are the stages of labor?
- stage 1 latent phase: cervical effacement and early dilation
- stage 1 active phase: more rapid cervical dilation, usually beginning at 6 cm
- stage 2: complete cervical dilation through the delivery of the infant
- stage 3: immediately after delivery of the infant until delivery of the placenta
- stage 4: the immediate postpartum period of about 2 hours after delivery of the placenta during which the patient undergoes physiologic adjustment
List the seven cardinal movements of labor.
- engagement
- flexion
- descent
- internal rotation
- extension
- external rotation
- expulsion
Describe the seven cardinal movements of labor.
- engagement: descent of the biparietal diameter below the pelvic inlet, usually days to weeks prior to labor in nulliparous women
- flexion: the head flexes against the chest to allow the smallest diameter of the head to present to the maternal pelvis
- descent of the presenting part through the birth canal
- internal rotation facilitates presentation of the smallest diameter
- extension to accommodate the upward curve of the birth canal
- external rotation to bring the face forward in relationship to the shoulders
What is the problem with laboring in a supine position?
it leads to compression of the vena cava by the uterus, reducing venous return and thus cardiac output, leading to hypotension
What is the position commonly used in the US for labor?
the dorsal lithotomy position
Why are laboring patients told to avoid oral ingestion of anything except clear fluids?
because if they require anesthesia, aspiration becomes a concern
What sort of fluids would you use to hydrate a laboring patient if oral hydration was insufficient?
- likely half normal saline or D5 half normal saline
- lactated fluids are contraindicated because of the metabolic acid deficit incurred by the lactate
What are lactated ringers contraindicated during labor?
because they incur a metabolic acid deficit
What vertebral levels transmit the pain associated with early and late labor?
- during the first stage, pain from the cervix travels along visceral afferents, which return to T10-T12 and L1
- as the head descends, the lower birth canal and perineum are distended and pain is transmitted along the somatic afferents comprising portions of the pudendal nerves entering at S2-S4
What is an epidural? What is spinal anesthesia?
- epidural: an infusion of local anesthetics or narcotics through a catheter into the epidural space
- spinal: a single injection of anesthetic which affords about two hours of relief
What are two regional forms of anesthesia available during labor?
epidural and spinal anesthesia
How is a pudendal block given?
the ischial spine is located through the vagina and the injection is made just inferomedially to the spine through the sacrospinous ligament
What are the benefits of an epidural over spinal anesthesia?
- it provides a continuous source of anesthesia
- it can be titrated to maintain the patient’s sense of touch and motor ability, facilitating participation in the birthing process
What is the primary complication of spinal anesthesia or epidural?
posdural puncture headache
When do we typically use local blocks during labor?
to provide anesthesia for episiotomies and repair of vaginal and perineal lacerations
When assessing a patient is stage one of labor, what is important to assess?
dilation, effacement, station, position, and the status of the membranes
How do we describe fetal position during labor?
- left/right, presenting part, anterior/posterior/transverse
- so if the babies face is to the left and facing the mom’s posterior then it would be right occiput anterior
What is the median combined time for stage 1 and 2 of labor for nulliparous and multiparous women?
- nulliparous: 5.9 hours
- multiparous: 4.3 hours
If patients get the urge to push during the first stage of labor, what does this indicate, what should you tell them, and why is this the case?
- it indicates the fetal head has likely descended and is applying pressure on the perineum
- tell them to avoid pushing
- if they push against the cervix before it is fully dilated and effaced, it will cause traumatic swelling, adding time to the process of dilation
What risks are associated with artificial rupture of membranes?
- increases the risk of infection
- increases the risk of umbilical cord prolapse if the head has not already engaged
Mothers shouldn’t begin pushing during labor until what point?
second stage
What is caput succedaneum?
edema of the fetal scalp caused by pressure on the fetal head by the cervix, which, like molding, may cause an overestimation of the amount of descent
What two fetal changes may cause an overestimation of fetal descent?
molding and caput succedaneum (edema of the scalp)
What are the indications for episiotomy?
there are no current indications for the procedure
What is the modified Ritgen maneuver?
a method for delivering the head with extension while supporting the perineal tissues
- place one hand over the vertex while the other exerts pressure through the perineum onto the fetal chin
- the chin can be delivered slowly this way, protecting the perineum
Describe how to assist with a delivery after the head begins to crown?
- use the modified Ritgen maneuver, placing one hand over the vertex while the other exerts pressure through the perineum to slowly deliver the chin
- turn the head so it is forward facing in relation to the shoulders
- apply downward pressure with a hand on both sides of the head to deliver the anterior shoulder
- apply upward traction to deliver the posterior shoulder
What indications are there that the placenta has separated from the uterus?
- the uterus becomes globular
- there may be a gush of blood
- there may be a lengthening of the umbilical cord
What is the feared complication of applying too much traction to the placenta before it has separated from the uterus passively?
this may result in inversion of the uterus with profound blood loss and shock
What technique is used to deliver the placenta?
apply gentle downward traction on the umbilical cord while the abdominal hand applies gentle suprapubic counter pressure to secure the uterine fundus and prevent inversion
What medical therapies are available for the treatment of uterine atony?
- oxytocin
- methylergonovine maleate
- prostaglandins such as carboprost or misoprostol
What is the incidence and what are the risk factors for postpartum uterine hemorrhage?
- incidence of 1%
- most commonly occurs in the first hour after delivery of the placenta
- more likely in cases of rapid labor, protracted labor, intrapartum chorioamnionitis, or uterine enlargement secondary to LGA, polyhydramnios, or multiple gestations
What are three methods for inducing labor?
oxytocin administration, cervical ripening, and manipulation of the amnionic membranes
What are the benefits and risks of higher, more frequent dosing regimens of oxytocin for induction?
- result in shorter time in labor, reduce risk of chorioamnionitis, fewer numbers of c-sections for dystocia
- increases the risk of uterine hyperstimulation
How is cervical ripening performed?
with misoprostol or laminaria, a hygroscopic rod which expands within the cervix
Compare and contrast misoprostol vs. laminaria for induction of labor.
- misoprostol is administered vaginally; increases the risk of uterine hyper stimulation and thus contraindicated in those with previous c-section or uterine surgery for fear of rupture
- laminaria is a hygroscopic rod which expands to slowly dilate the cervix but may be ineffective or cause cervical laceration, inadvertent ROM, or infection
What are the complications associated with swelling of amniotic membranes?
infection, bleeding from undiagnosed previa, or accidental ROM
Why don’t we recommend routine early amniotomy?
it may modestly reduce the length of labor but may also result in an increased rate of intra-amniotic infection, umbilical cord prolapse, rupture of vasa previa, vertical transmission of HIV, and c-section for fetal heart rate abnormalities
What are the advantages of vaginal delivery?
reduces the risks of hemorrhage and infection, requires a shorter postpartum hospital stay, and is less painful with amore rapid recovery
TOLAC is only an option under what circumstances?
a lower transverse c-section rather than a classical c-section with an incision in the muscular upper portion of the uterus
What is the risk of uterine rupture during TOLAC?
about 1%
What is dystocia?
another name for abnormal labor
How do we define labor?
as the occurrence of uterine contractions of sufficient intensity, frequency, and duration to bring about demonstrable effacement and dilation of the cervix
What is a tocodynamometer?
an external gauge placed on the maternal abdomen which records the frequency of uterine contractions and relaxations as well as the duration of each
How does a tocodynamometer differ from an intrauterine pressure catheter?
a tocodynamometer is an external monitor rather than internal and doesn’t provide a record of the pressure generated by uterine contractions as an IUPC does
What is considered adequate uterine contraction?
- at least 25 mmHg of peak pressure
- 3-5 contractions in a 10-minute interval
What is the optimal intrauterine pressure during a contraction for the purpose of cervical dilation and fetal descent?
- 25 mmHg peak is adequate
- 50-60 mmHg is optimal
What is uterine hyperstimulation? Why is it a problem?
it is a consequence of various induction or augmentation therapies, which trigger contractions too frequently, eliminating necessary rest intervals during which the fetus receives unimpeded blood flow
What happens if the uterus contracts too frequently? What is this threshold?
with more than 5 contractions in a 10-minute period, there are insufficient rest intervals which means the fetus has inadequate periods of unimpeded blood flow
What is a montevideo unit? What is considered adequate for or consistent with normal progress of labor?
- a measure of uterine contraction measured as the number of contractions in 10 minutes times the average intensity above baseline intrauterine pressure
- 200 or more MVU is associated with normal progress
What size fetus is associated with a greater risk of dystocia?
one that is 4000-4500 grams
What is a mentum anterior face presentation?
one in which the face is the presenting feature but the chin is toward the mother’s abdomen, allowing for possible vaginally delivery if the fetal head undergoes flexion rather than normal extension
What is a compound presentation?
one in which one or more limbs prolapse alongside the presenting part
What sort of presentations might necessitate a c-section?
- face presentation, except mentumu anterior face presentation
- breech presentation
- persistent occipitoposterior
- refractory compound presentation
What do we call it when the size of the maternal pelvis is inadequate for the size of the presenting part of the fetus?
cephalopelvic disproportion
Through what mechanism may an epidural contribute to dystocia?
it may decrease the tone of the pelvic floor musculature, reducing the expulsive force
What risks are associated with dystocia?
- chorioamnionitis
- fetal infection and bacteremia, including pneumonia
- risk of cesarean or operative delivery
What are the two categories of labor abnormalities?
protraction, which is slowed progress, and arrest, in which labor has ceased
How do we define protraction or arrest disorder in the first stage of labor?
protraction
- a first stage, latent phase of more than 20 hours in a nulliparous woman or 14 hours in a multiparous woman
- a first stage, active phase with less than 1 cm/hour cervical dilation in a nulliparous woman or less than 1.2 cm/hour in a multiparous woman
arrest
- no cervical dilation for more than 2 hours in a nulliparous or multiparous woman
- no cervical dilation for more than 4 hours in a woman with regional anesthesia
How is protracted labor in the first stage managed?
- usually with observation or sedation
- if they continue to experience prolonged labor into the active phase, the patient may require augmentation with oxytocin or amniotomy
What qualifies for each of the following:
- protracted latent phase, stage 1 labor
- protracted active phase, stage 1 labor
- arrested active phase, stage 1 labor
- protracted stage 2 labor
- arrested stage 2 labor
- protracted latent phase, stage 1 labor: duration of more than 20 hours or 14 hours in nulliparous or multiparous women
- protracted active phase, stage 1 labor: cervical dilation rate of <1 cm/hour or <1.2 cm/hour in nulliparous or multiparous women
- arrested active phase, stage 1 labor: no cervical dilation for more than 2 hours without or 4 hours with regional anesthesia
- protracted stage 2 labor: more 2 hours without or 3 hours with regional anesthesia or less than 1 cm descent per hour
- arrested stage 2 labor: no descent after 1 hour of pushing
How do we define protracted and arrested labor in the second stage?
- protracted: duration of more than 2 hours without or 3 hours with regional anesthesia or less than 1 cm of descent per hour
- arrested: no fetal descent for one hour
What is labor augmentation?
methods for stimulation of uterine contractions when spontaneous contractions have failed to result in progressive cervical dilation or descent (i.e. mechanisms for treating protraction disorder of labor)
What are the two most commonly used methods for labor augmentation?
oxytocin and amniotomy
Why does amniotomy serve as augmentation?
because it allows the fetal head rather than the amniotic sac to be the dilating force
Amniotomy
- a method of augmentation; there are no indications for routine early amniotomy
- functions to treat protracted labor by allowing the fetal head rather than the amniotic sac to be the dilating force
- risks include decelerations due to cord compression and increased incidence of chorioamnionitis
What is uterine tachysystole?
more than 5 contractions in a 10-minute period, averaged over 30 minutes
Which is an absolute indication for operative or cesarean delivery, protracted or arrested delivery?
neither is an absolute indication and neither poses a risk to the mother or fetus in and of itself; each can be allowed to continue or be augmented as long as fetal monitoring is reassuring and cephalopelvic disproportion has been ruled out
Operative Vaginal Delivery
- one using direct traction on the fetal skull applied with forceps or vacuum
- classified as outlet, low, or mid pelvis depending on if the presenting part is at station 5+, 2+, or higher
- indications include protraction or arrest of second stage labor, suspicion of immediate or potential fetal compromise, or shortening of the second stage for maternal benefit
- contraindications include less than 34 weeks gestation due to the risk of intraventricular hemorrhage, known bone demineralization condition, known bleeding disorder, or fetal head that is unengaged or in an unknown location
- complications of forceps include perineal trauma, pelvic floor injury, and brain, spine, MSK, or corneal injury
- complications of vacuum are neonatal intracranial hemorrhage, subgaleal hematoma, scalp laceration, hyperbilirubinemia, cephalotoma, or retinal hemorrhage
What are the complications and risks associated with forcep delivery?
- perineal trauma, hematoma, or pelvic floor injury in mom
- injuries to brain or spine, musculoskeletal structures, or cornea
What are the complications and risks associated with vacuum delivery?
intracranial hemorrhage, smbgaleal hematoma, scalp laceration, hyperbilirubinemia, cephalotoma, and retinal hemorrhage in the neonate
What are the risk factors for breech presentation?
risk factors include prematurity, multiple gestations, polyhydramnios, hydrocephaly, anencephaly, aneuploidy, uterine anomalies, and uterine tumors
What are frank, complete, and incomplete breech presentation?
- frank: the butt is down with the hips fully flexed and knees extended with the feet at the head
- complete: the legs are crossed as if sitting on the floor
- incomplete: one or both feet are extended downward
External Cephalic Version
- a method of applying pressure to the mother’s abdomen to turn a breech fetus and achieve a vertex presentation
- good candidates are those at more than 36 weeks gestation, reassuring fetal heart tracing, adequate amniotic fluid, undescended, and without placental abruption or previa
- carries a fifty percent success rate
- but risks include PROM, abruption, cord accident, and uterine rupture
- should administered RhoGam at the time of the procedure
Which fetuses are good candidates for external cephalic version?
those after 36 weeks who are undescended with adequate amniotic fluid and reassuring heart tracings
Shoulder Dystocia
- associated with increased birth weight, maternal diabetes, and previous history of shoulder dystocia
- may be indicated by the turtle sign
- treated with McRoberts maneuver, suprapubic pressure, delivery of the posterior arm, Zavanelli maneuver, or intentional clavicle fracture
- often worsened by fundal pressure
What interventions are available for cases of should dystocia?
- McRoberts maneuver in which the mother’s legs are hyper flexed to the abdomen
- application of suprapubic pressure to dislodge the impacted shoulder
- delivery of the posterior arm
- Zavanelli maneuver in which the fetal head is flexed and reinserted into the vagina to re-establish cord blood flow and allow for c-section
- intentional clavicular fracture
What happens to the fetus after uteroplacental insufficiency occurs?
- there is fetal hypoxia
- blood is shunted to the brain, heart, and adrenals
- the heart responds with transient, repetitive, late decels
- there is an eventual switch to anaerobic glycolysis with metabolic acidosis
- as lactic acid accumulates the brain and myocardium become damaged
Neonatal Encephalopathy
- a clinically defined syndrome of disturbed neurologic function in the earliest days of life in a term infant
- manifests as difficulty initiating and maintaining respiration, depression of tone and reflexes, subnormal levels of consciousness, and seizures; however, these are not always permanent
- one specific, but uncommon, subtype is hypoxic-ischemic encephalopathy which is caused by the limitation of oxygen and blood flow near the time of birth
How common is hypoxic-ischemic encephalopathy?
it is an uncommon cause of neonatal encephalopathy, which is more commonly caused by factors present before the onset of labor
What is cerebral palsy?
a chronic disability of the CNS characterized by aberrant control of movement and posture appearing early in life and not as a result of progressive neurologic disease
Which form of cerebral palsy is associated with antepartum or intrapartum interruption of fetal blood supply?
spastic quadriplegia
How do we describe fetal heart rate?
- baseline rate
- variability
- presence of accelerations
- periodic or episodic decelerations
- changes in these characteristics over time
- and the overall classification as I, II, or III
Abnormal fetal heart rate patterns are indicative of what? What is the limitation with this association?
- it is associated with severe asphyxia
- however, the false positive rate is very high and most patients even with non reassuring FHR patterns give birth to healthy infants
What is considered a normal fetal heart rate? What is non-reassuring?
baseline of 110-160 is considered normal and 80-100 is considered non-reassuring
What is the most common cause of fetal tachycardia? What are other possible causes?
- chorioamnionitis is most common
- maternal fever, thyrotoxicosis, medication, and fetal arrhythmia are all possible causes
What is considered normal fetal heart rate variability? What does diminished variability indicate?
- normal is 6-25 bpm
- 5 or less is indicative of fetal hypoxia, academia, drugs that depress the fetal CNS, fetal tachycardia, fetal CNS and cardiac anomalies, prolonged uterine contractions, prematurity, and fetal sleep
How do we define baseline fetal heart beat?
- it is the mean FHR rounded to increments of 5 during a 10-minute segment for a minimum of 2 minutes
- it is indeterminate if no baseline is present for more than 2 minutes
How do we define and describe fetal heart rate accelerations?
- they are abrupt increases, meaning onset to peak is less than 30 seconds
- after 32 weeks, it has a peak of 15 bpm above baseline with a duration of 15 seconds or more but less than 2 minutes
- before 32 weeks, it has a peak of 10 bpm above baseline for 10 seconds or more but less than 2 minutes
What is an acceleration that lasts 15 seconds, between 2 and 10 minutes, and more than 10 minutes?
- an acceleration
- a prolonged acceleration
- a baseline change
What is an early deceleration?
a visually symmetrical gradual decrease and return where the nadir takes at least 30 seconds to reach and coincides with the peak of a contraction
What is a late deceleration?
a visually symmetrical gradual decrease and return where the nadir takes 20 seconds ore more to reach and for which the nadir does not coincide with the peak of a contraction
What is a variable deceleration?
an abrupt decrease in FHR taking less than 30 seconds to reach nadir, which is more than 15 bpm lower than baseline and lasts 15 to 120 seconds, and not associated with uterine contractions
What is a prolonged deceleration?
one lasting more than 2 minutes but less than 10
What causes early, late, and variable FHR decelerations?
- early are normal and due to pressure on the fetal head from the birth canal, which triggers a reflex through the vagus nerve
- late are due to placental insufficiency
- variable are associated with cord compression and oligohydramnios
What qualifies as a category III fetal heart rate pattern?
- absent baseline variability and either recurrent late decels, recurrent variable decels, or bradycardia
- or a sinusoidal pattern
What qualifies as a category I fetal heart rate pattern?
- baseline rate between 110-160 with moderate variability
- absent late or variable decelerations
- accelerations and early decelerations may or may not be present
What are four methods for fetal stimulation?
- scalp sampling
- clamp scalp stimulation
- digital scalp stimulation
- vibroacoustic stimulation
If accelerations are present on the fetal heart tracing, this can help you exclude what?
acidosis
Meconium consists of what?
amniotic fluid, lanugo, bile, fetal skin, and intestinal cells
