Obstetrics Flashcards
What percent of the population is 1SD?
68%
What percent of the population is 2SD?
95%
What percent of the population is 3SD?
99.7%
Define sensitivity
The ability to correctly diagnose the disease in the patient
Given that the patient has the disease, what are the chances the test will be positive?
TP/(TP + FN)
Define specificity
The ability to correctly exclude disease in the patient
Given that the patient does not have the disease, what are the chances that the test will be negative?
TN/(TN + FP)
Define PPV
chance that a positive result is correct
Given that the test is positive, what are the chances the patient has the disease?
TP/(TP + FP)
Define NPV
chance that a negative result is correct
Given that the test is negative, what are the chances that the patient does not have the disease?
TN/(TN + FN)
Define incidence
new cases over a given period of time
define prevalence
total cases at a specific point in time
T4 dermatome
areola
T7 dermatome
xiphisternum
T10 dermatome
umbilicus
L1-2 dermatome
pubis
S3-5 dermatome
perineum
pudendal nerve roots
S2-4
What areas does the pudendal nerve innervate?
perineum, lower buttocks, anus, rectum, vulva, labia, and clitoris
Nerve innervation of first stage of labor
T11-T12 (and adjacent dermatomes T10-L1)
Nerve innervation of second stage of labor
pudendal nerve S2-S4 (and adjacent dermatomes T12-L1)
What nerve roots are damaged with Erb’s Paralysis?
C5-C6
What is the physical finding in Erb’s paralysis?
arm hangs at side medially rotated (waiter’s tip) with grasp reflex intact
What nerve roots are damaged with Klumpke’s Paralysis?
C8-T1
What is the physical finding in Klumpke’s paralysis?
hand and wrist paralysis, arm hangs at side, grasp reflex lost
What are the three components of clinical pelvimetry?
- pelvic inlet
- mid-pelvis
- pelvic outlet
How is the pelvic inlet evaluated?
obstetrical conjugate
What is the obstetrical conjugate measuring and how is it calculated? What is a normal measurement?
midportion of the symphysis pubis to the sacral promontory
diagonal conjugate - 2cm
greater than or equal to 8cm
What is the diagonal conjugate? What is a normal measurement?
lower portion of the symphysis pubis (thumb) to the sacral promontory (tip of index finger)
greater than or equal to 10cm
How is the mid-pelvis evaluated?
AP diameter and interspinous diameter at the level of the ischial spines
How is the AP diameter measured? What is a normal measurement?
symphysis (thumb) to deep part of the pelvis aka contour of the sacrum aka ischial spine (tip of index finger)
greater than or equal to 11.5cm
How is the interspinous diameter measured? What is a normal measurement?
the smallest distance between the ischial spines.
greater than or equal to 10cm
How is the pelvic outlet evaluated?
two triangles based on the ischial tuberosities
1. apex at tip of sacrum
2. apex at pubic arch
What are the 4 pelvic types? What is the classification called?
- gynecoid
- anthropoid
- android
- platypelloid
Caldwell-Moloy Classifications
How is a gynecoid pelvis shaped?
round/slightly oval in transverse axis
How is an anthropoid pelvis shaped?
oval in AP axis
how is an android pelvis shaped?
heart shaped with anterior narrow apex
How is a platypelloid pelvis shaped?
oval in transverse axis
What shape pelvis is a/w 1st or 2nd stage arrest?
anthropoid pelvis, often can lead to OP arrest
What shape pelvis is a/w 1st stage arrest?
android pelvis because of the sacro-sciatic notch
What shape pelvis is a/w OT arrest?
platypelloid pelvis
What muscles are cut with midline episiotomy
- superficial transverse perineal
- bulbocavernosus (aka bulbospongiosis)
- deep transverse perineal
- external anal sphincter
What muscles are cut with mediolateral episiotomy
- superficial transverse perineal
- bulbocavernosus (aka bulbospongiosis)
- deep transverse perineal
What is the lie of the fetal presentation?
the angle of the fetus in relation to the mother and the uterus.
longitudinal vs oblique vs transverse
What is the fetal presentation?
a reference to the part of the fetus that is overlying the maternal pelvic inlet
for longitudinal lie: vertex vs breech vs face
for transverse lie: back
for transverse/oblique lie: shoulder
What is the position of the fetal presentation?
The relation of the fetal back to the right or left side of the mother and whether it is directed anteriorly or posteriorly.
anterior vs posterior
up vs down
What is the denominator of the fetal presentation?
the part of the fetus that is used to describe positions for presentation.
vertex = occiput
breech = sacrum
face = mentum
shoulder = acromion/scapula
What is the attitude of the fetal presentation?
The relation of fetal parts to each other.
moving along y-axis
Flexion in the majority of cases.
Extension in face presentation.
What is the synclitism of the fetal presentation?
The posture in which the 2 parietal bones are at the same level.
asynclitic is when the sagittal suture is shifted along the x-axis
What is the station of the fetal presentation?
Station 0 the vertex at the level of ischial spines.
Stations -1, 2 and 3 represent 1, 2 and 3 cm respectively above the level of ischial spines.
Stations +1, +2 and +3 represent 1, 2 and 3 cm respectively below the level of ischial spines.
What are the components of the Leopold’s maneuvers?
- Which fetal part is occupying the fundus?
- On which side is the back lying?
- What occupies the lower uterine pole?
- Is the head flexed or extended?
What are the steps of the mechanisms of labor?
- engagement
- descent
- flexion
- internal rotation
- extension
- restitution
- external rotation
- expulsion
What are the accelerations expected on the fetal heart rate tracing before 32wks? After 32wks?
10x10s
15x15s
What components of the fetal heart rate tracing are predictive of normal fetal acid/base status?
presence of accelerations and and/or moderate variability
What are the criteria for BPP?
Within 30 minutes:
1. reactive NST
2. 1 episode of breathing in 30 seconds
3. 1 flexion/extension (tone)
4. 2cm DVP
5. 3 gross movements
How do you manage a BPP of 8-10?
normal, expectant management
How do you manage a BPP of 6?
equivocal
if term, deliver
if preterm, repeat in 24hrs
How do you manage a BPP of 4 or less?
abnormal
deliver
What are the 5 components of the Apgar score?
Heart rate, respiratory rate, muscle tone, reflex/irritability, color
Activity, Pulse, Grimace, Appearance, Respiration
How do you calculate Apgar points for heart rate?
Absent: 0
< 100: 1
> 100: 2
How do you calculate Apgar points for respiratory rate?
Absent: 0
slow, irregular: 1
good, crying: 2
How do you calculate Apgar points for muscle tone?
flaccid: 0
mild flexion: 1
active motion: 2
How do you calculate Apgar points for reflex/irritability?
no response: 0
grimace: 1
vigorous cry: 2
How do you calculate Apgar points for color?
blue, pale: 0
pink body, blue extremities: 1
completely pink: 2
What is the protocol for calculating apgars?
If < 7 at 5 minutes, continue apgar scores q5 mins until 20mins
What are the components for calculating a bishop score?
dilation, effacement, station/descent, position, consistency
How do you calculate points in the bishop score for dilation?
closed: 0
1-2: 1
3-4: 2
5+: 3
How do you calculate points in the bishop score for effacement?
0-30: 0
40-50: 1
60-70: 2
80+: 3
How do you calculate points in the bishop score for descent/station?
-3: 0
-2: 1
-1, 0: 2
+1, +2: 3
How do you calculate points in the bishop score for position?
posterior: 0
mid: 1
anterior: 2
How do you calculate points in the bishop score for consistency?
firm: 0
medium: 1
soft: 2
Define failed induction of labor
- lack of progress in early labor, and
- SROM or AROM present, and
- at least 12-18hrs of oxytocin after ROM
- no other indication for delivery is present
define active phase arrest of labor
dilation of at least 6cm with ROM and no cervical change for
- at least 4hrs of adequate contractions
- at least 6hrs w/ inadequate contractions w/ oxytocin augmentationd
define adequate contractions
greater than or equal to 200 MVUs
What are some considerations in the first stage of labor management to help move things along?
- early amniotomy in induced labor to reduce duration of labor
- in protracted first stage of labor, active management with oxytocin augmentation to reduce operative deliveries
- continuous emotional support/doula
- peanut ball/pretzel positioning
- hydration (IV vs PO)
- amnioinfusion if necessary
Define prolonged second stage of labor
- greater than 3hrs pushing in a nulliparous patient
- greater than 2hrs pushing in a multiparous patient
What are some considerations during second stage of labor management?
- commence pushing with full cervical dilation, no laboring down
- IUPC appropriate to document forces
- manual head rotation is favored
How is second stage arrest individualized?
- prolonged 2nd stage criteria met
- consideration of patient morbidities and risks
- shared decision-making, patient preferences
How can the diagnosis of prolonged 2nd stage of labor be made earlier than the 2-3hr mark?
lack of fetal rotation or descent with adequate contractions documented and adequate pushing forces
How do you manage an active phase arrest of labor?
cesarean delivery
How do you manage prolonged second stage of labor?
- assessment for operative vaginal delivery
- cesarean delivery
How do you manage an unsuccessful induction of labor?
- individualized management
- cesarean delivery
In what cases is an IUPC indicated?
- inadequate response to oxytocin
- absence of 1:1 nursing
- obesity
How are MVUs calculated?
summation of the amplitude above baseline of all contractions in a 10min period
What are the indications for an operative vaginal delivery?
- prolonged second stage of labor
- suspected impending fetal compromise
- to shorten the 2nd stage of labor for maternal indication
What are the contraindications to an operative vaginal delivery?
- fetal head unengaged
- position of fetal head unknown
- fetal conditions including bleeding disorder (VWF, low plts, hemophilia) and bone demineralization disorder (OI)
- no facility/staff for emergency C/D
- <34wks w/ VAVD
What are the prerequisites for operative vaginal delivery?
- informed consent
- engaged head (largest diameter of the head is at/below level of the ischial spines)
- cervix fully dilated
- amniotic membranes ruptured
- known position (station, position, attitude, synclitism)
- adequate pelvis, fetal weight estimation done
- operator appreciation of mechanism of labor
- operator expertise with forceps/vacuum
- adequate aneshesia
- empty bladder/rectum
- patient appropriately positioned
- vertex (exception: piper forceps)
- facilities to perform CD if necessary
What are the criteria for using outlet forceps?
- scalp visible at introitus w/o separating labia
- fetal skull at pelvic floor
- fetal head is at or on perineum
- head in OA or OP position
- rotation not exceeding 45 degrees
What are the criteria for using low forceps?
- vertex higher than outlet forceps but below +2 station
- fetal skull at least +2 station
- fetal head is not at perineum
- head in OA or OP position
- rotation not exceeding 45 degrees
low forceps with rotation if rotation is greater than 45 degrees
What are the criteria for using mid forceps?
not done anymore
1. station above +2 station
2. head engaged
3. appropriate option in select clinical circumstances
what are complications of operative vaginal delivery to the fetus?
- scalp/facial laceration
- cephalohematoma
- retinal hemorrhage (38% w/ VAVD, also common with precipitous deliveries, usually temporary)
- subgaleal hematoma (30-40%)
- intracranial hemorrhage
- sp forceps: facial laceration, facial nerve palsy, skull fracture
what are complications of operative vaginal delivery to the mom?
obstetrical laceration & pelvic hematoma
What was the consensus of the ANODE trial?
administer a single dose of IV abx in operative vaginal delivery when
1. episiotomy is performed
2. 3rd or 4th degree laceration present
current ACOG recommendation is to administer a single dose 2nd gen cephalosporin IV at time of 3rd or 4th degree repair
define macrosomia
fetal weight at least 4500g regardless of gestational age
define LGA
weight relative to gestational age, greater than 90%ile for any given gestational age
What is the incidence of macrosomia
1.5%
What are the risks of shoulder dystocia with macrosomia?
15%
What are the risks of shoulder dystocia without macrosomia?
1.5%
What are the risks of shoulder dystocia with macrosomia and diabetes?
25%
What is the risk of brachial plexus injury without macrosomia?
0.1%
What is the risk of brachial plexus injury with macrosomia?
5%
what percentage of brachial plexus injuries are permanent?
10%
What is the hadlock criteria error for macrosomic fetuses?
13%
What is the hadlock criteria error for non-macrosomic fetuses?
8%
What is the typical weight distribution in macrosomic infants?
AC > BPD/HC
What are some interventions to reduce risk of macrosomia?
- exercise during pregnancy
- low-glycemic diet in women with GDM
- pre-pregnancy bariatric surgery in women with class 2/3 obesity
What are some risk factors for macrosomia?
- history of macrosomia
- maternal obesity
- excessive weight gain in pregnancy
- gestational age > 40wks
- GDM
- positive 1hr GTT and negative 3hr GTT
Is macrosomia an indication for CD? Why or why not?
no, CD rate will rise (up to 2x), no reduction in shoulder dystocia
in what setting is macrosomia an acceptable indication for CD?
if EFW is at least 5000g for non-diabetics. at least 4500g for diabetics
Is CD indicated for macrosomic fetuses <4500/5000 g to reduce birth trauma risk?
No
How many c/s to prevent 1 birth injury in a non-diabetic macrosomic baby weighing <5000g?
3700
How many c/s to prevent 1 birth injury in a diabetic macrosomic baby weighing <4500g?
440
Is TOLAC contraindicated for macrosomia?
No
is operative vaginal delivery contraindicated for macrosomia?
No
In what situation is emergency CD under local anesthesia appropriate?
extreme emergency, no skilled anesthetist available, patient counseled and consented
What is the dosing for local anesthetic for CD
lidocaine 7mg/kg 0.5% with epinephrine (to keep anesthetic from spreading)
maximum dose 500g (100cc)
monitor EKG/SA O2
What are the side effects of lidocaine (in order of increasing toxicity)?
metallic taste in mouth
peri-oral numbness
tinnitus
slurred speech/blurred vision
altered consciousness
convulsions
cardiac arrhythmias
cardiac arrest
What is the proper technique for emergency CD under local anesthesia?
- midline incision preferable (quicker, less bleeding)
- infiltrate skin, parietal and visceral peritoneum (uterine serosa)
- avoid intravascular injection
- do not manipulate bowel
- do not pack gutters
- do not exteriorize uterus
- monitor with continuous EKG and SA O2
What is the neonatal survival rate following maternal cardiac arrest if delivered within 15 mins?
greater than 67%
What is the neonatal survival rate following maternal cardiac arrest if delivered in 16-25 mins?
less than 50%
In what time frame of delivery following maternal cardiac arrest does the baby have the best chances of survival?
<5 mins
why is it considered a resuscitative hysterotomy if maternal CPR is unsuccessful during cardiac arrest?
CPR provides <30% of normal CO in a gravid uterus at or above the umbilicus, compressions are less effective with enlarged uterus
What is the current VBAC rate?
13.8%
What is the risk of uterine rupture in the setting of TOLAC with previous LTCS?
<1%
What is the risk of uterine rupture in the setting of TOLAC with an undocumented scar?
no increased rupture risk, <1%
What is the risk of uterine rupture in the setting of TOLAC with twins?
no increased rupture risk, <1%
What is the risk of uterine rupture in the setting of TOLAC with previous low segment rupture?
6%
What is the risk of uterine rupture in the setting of TOLAC with previous upper segment rupture?
32%
What is the risk of uterine rupture in the setting of TOLAC with previous classical uterine incision?
10%
What is the risk of uterine rupture in the setting of TOLAC with induction with PgE1?
5-10%
What is the risk of uterine rupture in the setting of TOLAC with induction with PgE1 for 2nd trimester IUFD?
<1%
What is the risk of uterine rupture in the setting of TOLAC with prior x2?
1-1.8%
What is the risk of uterine rupture in the setting of TOLAC with oxytocin induction?
1-1.5%
What are the contraindications to TOLAC?
previous uterine rupture
previous classical CD or T-incision
extensive transfundal surgery
Who are appropriate candidates for TOLAC?
1 or 2 previous LSTC/S
previous low vertical CD
previous CD for unknown scar
twin gestation
What is the overall probability for a successful VBAC?
60-80%
What is the VBAC rate if the previous CD was for CPD?
66%
What is the VBAC rate if the previous CD was not for CPD?
75%
what can increase the success rate of a TOLAC?
prior vaginal birth
spontaneous labor
