USMLE Step 2 — Lesson 1 OBSTETRIC
Highlights
USMLE Step 2
Elmar P. Sakala, MD, MPH
Discrepant Fundal Size
Case #1
• A 20 y/o woman comes to the out-pt prenatal clinic for a new OB visit.
• She is 30 wks gest by LMP.
• Fundal measurement is 24 cm.
Fundus smaller than dates
Differential Diagnosis
Fundus smaller than dates
Think of 3 uterine compartments:
o Fetal: fetal demise, IUGR
o Amniotic fluid: oligohydramnios
o Placental: molar preg
Diagnosis
Fundus smaller than dates
Obtain OB ULTRASOUND:
o Fetal: cardiac motion, fetal biometry (BPD, HC, AC, FL)
o Amniotic fluid: 4-quad AFI <5 cm
o Placental: texture, appearance
Etiology
Intrauterine Growth Restriction
SYMMETRIC IUGR:
o BPD, HC, AC, FL are less than expected due to growth potential: e.g. aneuploidy, 1st trimester infection
ASYMMETRIC IUGR:
o AC is less than expected due to nutritional supply e.g. hypertension, preeclampsia
Etiology
Oligohydramnios
• Premature membrane rupture
• Urinary tract anomaly
• Placental insufficiency
• Meds: indomethacin, ACE inhibitors
Management
Fundus smaller than dates
• Details are specific to the problem identified.
Case #2
• A 20 y/o woman comes to the out-pt prenatal clinic for a new OB visit.
• She is 30 wks gest by LMP.
• Fundal measurement is 35 cm.
Fundus larger than dates
Differential Diagnosis
Fundus larger than dates
Think of 4 compartments:
o Fetal: multiple fetuses, macrosomia
o Amniotic fluid: polyhydramnios
o Placental: molar preg, fetal hydrops, infection
o Uterine: leiomyomas
Diagnosis
Fundus larger than dates
Obtain OB ULTRASOUND:
o Fetal: # of fetuses; fetal biometry (BPD, HC, AC, FL) shows macrosomia
o Amniotic fluid: 4-quad AFI >25 cm
o Placental: texture, appearance
o Uterus: leiomyomas
Etiology
Polyhydramnios
• Fetal GI tract: TE fistula, duod atresia
• Fetal NTD: spina bifida, anencephaly
• Fetal hydrops: immune, nonimmune
• Diabetes mellitus: poor glucose control
Management
Fundus larger than dates
• Details are specific to the problem identified.
USMLE Step 2 — Lesson 2 FIRST Trimester Bleeding
Case #3
• A 25 y/o woman comes to the out-pt prenatal clinic for a return OB visit.
• She has had vaginal bleeding with no cramping.
• She is 12 wks gest by LMP.
Differential Diagnosis
First trimester bleeding
• Threatened abortion
• Missed abortion
• Inevitable abortion
• Incomplete abortion
• Completed abortion
• Molar pregnancy
• Ectopic pregnancy
Diagnosis
First trimester bleeding
SYMPTOMS
o Bleeding? Passed tissue? Contractions?
Diagnosis
First trimester bleeding
SYMPTOMS:
o Bleeding? Passed tissue? Contractions?
PELVIC EXAMINATION
o Cervical lesion? Internal cervical os dilated?
Diagnosis
First trimester bleeding
SYMPTOMS:
o Bleeding? Passed tissue? Contractions?
PELVIC EXAMINATION
o Cervical lesion? Internal cervical os dilated?
ULTRASOUND:
o Gest sac? Embryo? Cardiac motion?
Diagnosis & Management
THREATENED abortion
Characteristics:
o Bleeding: minimal
o Cramping: none or minimal
o Internal cervical os: closed
o Ultrasound: normal findings
Management:
o Conservative management
Diagnosis & Management
MISSED abortion
Characteristics:
o Bleeding: none
o Cramping: none
o Internal cervical os: closed
o Ultrasound: non-viable pregnancy
Management:
o Scheduled D&C, RhoGAM if Rh-
Diagnosis & Management
INEVITABLE abortion
Characteristics:
o Bleeding: YES
o Cramping: YES
o Internal cervical os: dilated
o Tissue passed: none
o Ultrasound: POC remains in uterus
Management:
o Emergency D&C, RhoGAM if Rh-
Diagnosis & Management
INCOMPLETE abortion
Characteristics:
o Bleeding: YES
o Cramping: YES
o Internal cervical os: dilated
o Tissue passed: YES
o Ultrasound: POC remains in uterus
Management:
o Emergency D&C, RhoGAM if Rh-
Diagnosis & Management
COMPLETED abortion
Characteristics:
o Bleeding: Minimal
o Cramping: Minimal
o Internal cervical os: dilated
o Tissue passed: YES
o Ultrasound: Normal uterus stripe
Management:
o Observation; serial quantitative β-hCG (to r/o ectopic)
Diagnosis & Management
SEPTIC abortion
Characteristics:
o History: Non-sterile uterine instrumentation
o Bleeding: Minimal
o Cervical os: purulent discharge
o Uterus: tender
o Vital Signs: Fever, tachycardia
Management:
o Admit; cultures; IV gent & clindamycin; gentle D&C
SECOND Trimester Loss
Case #4
• A 25 y/o woman (G2 P1Ab1) at 18 wks gest presents to the hospital maternity unit
with pelvic pressure but NO contractions.
• On exam membranes are bulging to the introitus.
Second trimester loss
Differential Diagnosis
Second trimester loss
o Incompetent cervix
o Mullerian anomaly
o Submucus leiomyoma
Diagnosis & Management
Incompetent Cervix
Characteristics:
o Painless cervical dilation.
o Non-viable gest age.
o Delivery of immature normal fetus that dies.
Management:
o Cervical cerclage (emerg now if possible; scheduled at 14 wks next
pregnancy)
Cervical CERCLAGE
Diagnosis & Management
Mullerian anomaly
History:
• Regular contractions with cervical dilation.
• Non-viable gestational age.
• Delivery of immature normal fetus that dies.
Diagnosis: Hysteroscopy or HSG
Management: Hysteroscope resection if thin uterine septum; laparotomy if thick septum
Diagnosis & Management
Submucus leiomyoma
History:
• 2nd trim demise occurs without explanation.
• Non-viable gestational age.
• Delivery of stillborn normal fetus.
Diagnosis: Hysteroscopy or HSG
• Management: Hysteroscope resection.
THIRD Trimester Bleeding
Case #5
• A 25 y/o G2 P1Ab1 woman presents to the hospital maternity unit with painful vaginal
bleeding.
• She is 30 wks gest by LMP.
• Fetal heart tones are present.
THIRD trimester bleeding
Differential Diagnosis
THIRD trimester bleeding
• Abruptio placenta
• Placenta previa
• Vasa previa
• Uterine rupture
Diagnosis & Management
Abruptio Placenta
Findings:
o PAINFUL vag bleeding with uterus not relaxing between UCs.
o Assoc with PIH, cocaine, trauma, DIC
Sono: Normally implanted placenta
Management:
o Depends on gest age, status of Mom & fetus.
Normal
Placental
Implantation
- Fundal
- Anterior - Posterior
Overt
ABRUPTIO
Placenta
Concealed
ABRUPTIO
Placenta
Diagnosis & Management
Placenta previa
Findings:
o PAINLESS vaginal bleeding.
o Assoc with prev PP, twins,multiparity, AMA
Sono: placenta in lower uterine segment Types: Low-lying, partial, complete
Management:
o Depends on gest age, status of Mom & fetus.
Low
Lying
Placenta
Previa
Partial
Placenta
Previa
Total
Central
Placenta
Previa
Diagnosis & Management
Vasa previa
Findings:
o PAINLESS vaginal bleeding.
o Assoc with twins,accessory placental lobe
o Bleeding is fetal blood!
Triad: AROM, vag bleeding, fetal bradycardia
Management:
o Immediate cesarean on diagnosis!
VASA
Previa
TEST TAKING WORKSHOP
Barbara J. Irwin, BSN, RN
Diagnosis & Management
Uterine rupture
Findings:
o PAINFUL vaginal bleeding with UCs.
o Assoc: prev classical CS, XS oxytocin, trauma.
o Non-reassuring fetal monitor pattern.
Types: Complete, incomplete
Management:
o Immediate cesarean delivery on diagnosis!
USMLE Step 2 — Lesson 3 Postdates Pregnancy
Case #6
• A 24 y/o multigravida comes to the out-pt office for a return OB visit.
• She is now 42½ wks gest by LMP. Her first prenatal visit was 6 weeks ago.
• Her fundal height measures 41 cm.
• FHT are 145 beats/min. BP is 125/75.
POSTDATES pregnancy
Level of Question Difficulty
• Recall Recognition
• Comprehension
• Application
• Analysis
Diagnosis
POSTDATES pregnancy
• >42 weeks amenorrhea
(assuming ovulation occurred on day 14)
• >294 days amenorrhea
(assuming ovulation occurred on day 14)
• >280 days postconception
(time of conception is known)
Diagnosis
POSTDATES pregnancy
• Based on Amenorrhea 6-12% (false)
• Based on Conception 3-5% (true)
Hazards
POSTDATES pregnancy
PERINATAL
MORTALITY
3-fold
Fetus in Postdates Preg?
Key question: Placental Function?
75% Maintained
MACROSOMIA
Syndrome
Difficult Labor
& Delivery
Forceps, Vacuum
Shoulder Dystocia
Birth trauma
Cesarean Section
25% Deteriorates
DYSMATURITY
Syndrome
Placental
Insufficiency
Acidosis
Meconium aspiration
Oxygen deprivation
Cesarean Section
POSTDATES pregnancy
First Question to ask:
How much confidence do you have in the GESTATIONAL AGE?
Confirming gest age
POSTDATES pregnancy
• Menstrual history
sure; planned preg; normal cycle; no Ocs
• Clinical landmarks
uterine size & FHT<12 wk; quickening
• Sonogram dating
CRL <12 wk (+ or - 5d); BPD 12-18 wk (+ or - 7d)
Differential Diagnoses
POSTDATES pregnancy
• Dates sure
o cervix favorable
• Dates sure
o cervix Unfavorable
• Dates unsure
POSTDATES Management
Dates FIRM - Cx FAVORABLE
• 1 Induce labor: AROM, oxytocin
• Intrapartum EFM looking for:
o VARIABLE decels
umbilical cord compression
o LATE decels
placental insufficiency
POSTDATES Management
What about MECONIUM?
• Incidence:
4 times more common
• Mechanism:
bowel function or acidosis
POSTDATES Management
What about MECONIUM?
Management:
• Amnioinfusion
• Suction pharynx
• Tracheal aspiration
POSTDATES Management
Dates FIRM - Cx Unfavorable
• 1 Induce labor: prostaglandin E2
• Await spont labor looking for:
o NSTs reactive 2/week
o AFIs > 5-8 cm 2/week
POSTDATES Management
Dates UNSURE
• Await spont labor looking for:
NSTs reactive 2/week
AFIs > 5-8 cm 2/week
Hypertension in Pregnancy
HYPERTENSION in Preg
Effect of normal
physiologic changes of pregnancy
Case #7
• A 21 y/o primigravida at 32 wks gest comes for a routine OB visit.
• Her BP sitting is 155/95; repeat reading was 145/90.
• Urine dipstick protein is 3+.
• No previous history of HTN.
Hypertension in Pregnancy
Differential Diagnosis
Hypertension in Pregnancy
o Mild preeclampsia
o Severe preeclampsia
o Eclampsia
o HELLP syndrome
o Chronic HTN
MILD preeclampsia
SEVERE preeclampsia
ECLAMPSIA
Can be RAPID progression!
Preeclampsia should be renamed:
Diffuse
VASOSPASTIC
Disease of Pregnancy
AGGRESSIVE Management GUIDELINES:
• MAINTAIN BP diastolic 90-100 mm Hg
• Prevent CONVULSIONS with MgSO4
• Initiate DELIVERY rapidly
Diagnosis & Management
MILD Preeclampsia Findings:
• HTN > 140/90; proteinuria 1-2+; edema.
• Hemoconcent ( H&H, uric acid, BUN, creat)
• No Symptoms (HA, epig pain, visual ∆).
• No Signs (DIC, cyan, oliguria, pulm edema).
Management:
• Conservative – in hospital if < 36 wks gest
• Aggressive – if > 36 wks gest, IV MgS04
Diagnosis & Management
SEVERE Preeclampsia Findings:
• HTN > 160/110; proteinuria 3-4+; edema
• Any Symptoms (HA, epig pain, visual ∆).
• Any Signs (DIC, cyanosis, oliguria, pulmon edema).
Management:
• Conservative – in ICU if 26-33 wks gest if only HTN & proteinuria present;
hydralazine; MgS04; steroids.
• Aggressive – if <26 or >33 wks, or symptoms/signs; MgS04; steroid.
Diagnosis & Management
ECLAMPSIA
Findings:
• HTN > 140/90; proteinuria; edema
• New onset of generalized convulsions.
• May occur ante/intra/postpartum.
Management:
• Conservative – NEVER.
• Aggressive – as soon as diagnosis is made; hydralazine; IV MgS04; steroids.
Diagnosis & Management
HELLP syndrome
Findings:
• Hemolysis, Elev Liver enyz, Low Platelets.
• Other findings of preeclampsia.
• May occur ante/intra/postpartum.
Management:
• Conservative – NEVER.
• Aggressive – as soon as diagnosis is made; hydralazine; IV MgS04; steroids.
Diagnosis & Management
CHRONIC hypertension
Findings:
• Pre-existent HTN or HTN prior to 20 wks that persists past 6 wks PP.
• Proteinuria is variable.
Management:
• Conservative – Aldomet is drug of choice
• Aggressive – if superimposed preeclampsia; hydralazine; MgS04, steroids
Aggressive in-patient:
• Mild PIH : > 37 wks
• Severe PIH < 26 wks
• Severe PIH > 34 wks
• Severe PIH maternal jeopardy
• Severe PIH fetal jeopardy
• Chr HTN with PIH.. any GA
• Eclampsia………… any GA
• HELLP…………….. any GA
Glucose Intolerance in Pregnancy
Case #8
•
A 36 y/o multigravid at 28 wks gest.
•
•
1 hr 50 g glucose is 165 mg/dl.
•
•
3 hr 100 g OGTT is F-90; 1hr- 190 ; 2-hr 165 ; 3-hr 145 .
•
•
Urine dipstick glucose is 3+.
•
•
• DIABETES in Pregnancy
Differential Diagnosis
DIABETES in Pregnancy
• Gestational diabetes
• Type 1 diabetes mellitus
• Type 2 diabetes mellitus
Diagnosis
GESTATIONAL diabetes Findings:
o 2 of 4 values abnormal on 3 hr 100 g OGTT.
o Onset > 20 wks gestation (if true GDM)
o Onset any time during pregnancy.
o Due to hPL, placental insulinase, cortisol.
o No in fetal anomalies (if true GDM).
o Resolves after delivery (if true GDM).
Diagnosis
TYPE 1 diabetes mellitus Findings:
o Onset prior to pregnancy.
o Due to islet cell destruction.
o Plasma insulin level is .
o Fetal anomalies may be .
o Unable to achieve nonPG euglycemia without insulin.
Diagnosis
TYPE 2 diabetes mellitus Findings:
o Onset prior to pregnancy.
o Due to insulin resistance.
o Plasma insulin level is .
o Fetal anomalies may be .
o Is able to achieve nonPG euglycemia without insulin.
EUGLYCEMIA management
All Preg Glucose Intolerance
• Diet: ADA diet ( complex CHO). • Educ: Mom re glucose control.
• Exercise: Regular, consistent
• Targets: FBS 60-90; 1 hr PP <140
• Insulin: NPH & Reg human insulin if euglycemia not achieved with diet; split dose of
2/3 AM & 1/3 PM.
Anomaly detection
Type 1 & 2 Diabetes Mellitus
Most common anomalies
• NTD defects
• CHD defects
• Sacral agenesis
Anomaly detection
Type 1 & 2 Diabetes Mellitus
13-14 wk Sono anencephaly
16-18 wk MSAFP NTD
18-22 wk Focused sono other anomalies
22-24 wk Fetal echo cardiac anomalies
( if first trimester Hb A1C)
Anomaly PREVENTION
Type 1 & 2 Diabetes Mellitus
• Preconception
EUGLYCEMIA
• Preconception
FOLIC ACID 4 mg po /day
USMLE Step 2 — Lesson 4: Medical Complications of Pregnancy CARDIAC Disease in Pregnancy
Cardiac Disease in Preg
Effect of normal physiologic changes of pregnancy
Physiology of Pregnancy Cardiac
Formula for
Cardiac OUTPUT? (Volume of blood pumped by heart in 1 minute)
Physiology of Pregnancy Cardiac
Formula for
Cardiac OUTPUT?
(Volume of blood pumped by heart in 1 minute)
HR x SV
(Heart Rate x Stroke Volume)
Physiology of Pregnancy Cardiac
IF HR & SV
THEN
Cardiac Output
Case #9
• A 40 y/o multigravida at 18 wks gest comes to the out-pt clinic.
• History of rheumatic fever.
• SOB with mild activity.
• Pulse: 110/min; parasternal heave;
Gr 4/6 pandiastolic murmur.
Cardiac Disease in Preg
Significant Diagnoses
Cardiac Disease in Preg
• Mitral stenosis
• Eisenmenger’s syndrome
• Marfan’s syndrome
• Tetralogy of Fallot
Diagnosis & Management
Mitral STENOSIS Findings:
• Most common acquired heart disease.
• Problem: narrow valve diastolic filling.
• Results: LA Atrial fib, SBE, emboli.
CARDIAC Cycle: Diastole/Systole
CARDIAC Cycle: Diastole/Systole
CARDIAC Cycle: Diastole/Systole
Factors worsening
MITRAL STENOSIS?
• heart rate
• blood volume
• heart rate
• blood volume
Normal changes of PREGNANCY?
Factors worsening MITRAL STENOSIS:
heart rate
blood volume
Normal changes of PREGNANCY:
MITRAL STENOSIS:
Do not go well together
Normal changes of PREGNANCY:
Diagnosis & Management
Mitral STENOSIS
Findings:
o Most common acquired heart disease.
o Problem: narrow valve diastolic filling.
o Results: LA Atrial fib, SBE, emboli.
Management:
o Watch decompensation: PND, syncope, JVD.
o Avoid fluid overload: Na+ diet, diuretics.
o Avoid tachycardia: anemia, exercise, sedation.
o Vag delivery; invasive monitoring; SBE prophylax
Cardiac Disease in Preg
STENOTIC lesions are tolerated
POORLY.
USMLE Step 2 — Lesson 5: Management of Labor Abnormal
Labor
ABNORMAL LABOR
STAGES of NORMAL LABOR
Case 12
• A 32 y/o multigravida at 39 wks gest in the maternity unit has UCs every 3-4
minutes.
• Her cervix is 1-2 cm dilated and has been the same for the past 16 hours.
• Fetal monitor strip is reassuring.
ABNORMAL labor
Significant Diagnoses
ABNORMAL labor
• Prolonged latent phase
• Prolonged active phase
• Active phase arrest
• Arrest of descent
Diagnosis & Management
Prolonged LATENT phase Findings:
• Cervical dilation < 3 cm with UCs present.
• No labor progress >14 hrs in multipara.
• No labor progress >20 hrs in primipara
Cause:
• Injudicious analgesia, hypo/hypertonic UCs.
Management:
• Therapeutic rest or sedation; avoid cesarean.
Causes of ACTIVE phase problems:
• PELVIS
• Passenger
• Powers
PROBLEMS with MATERNAL
BONY PELVIS
How much can you change PROBLEMS with
MATERNAL BONY PELVIS?
How much can you change PROBLEMS with
MATERNAL BONY PELVIS?
NONE!
Causes of ACTIVE phase problems:
• Pelvis
• PASSENGER
• Powers
PROBLEMS with IN-UTERO FETAL
ORIENTATION
Nomenclature for IN-UTERO FETAL ORIENTATION
• Fetal LIE
• Fetal PRESENTATION
• Fetal POSITION
• Fetal ATTITUDE
• STATION
Terms to remember:
Orientation of Fetus In-utero
Fetal LIE Relationship between long axis of the
fetus & long axis of mother
Most common: LONGITUDINAL
Terms to remember:
Orientation of Fetus In-utero
PRESENTATION Portion of fetus overlying the pelvic inlet
Most common: CEPHALIC
Terms to remember:
Orientation of Fetus In-utero
POSITION Relationship between a reference point on the presenting fetal part & maternal bony
pelvis
Most common: OCCIPUT ANTERIOR
Terms to remember:
Orientation of Fetus In-utero
ATTITUDE Degree of flexion or extension
of fetal head
Most common: VERTEX
Terms to remember:
Orientation of Fetus In-utero
STATION Degree of descent of the presenting part through birth canal
(Expressed in cm above or below maternal ischial spine)
How much can you change PROBLEMS with IN-UTERO FETAL ORIENTATION?
How much can you change PROBLEMS with IN-UTERO FETAL ORIENTATION?
Very little!
Causes of ACTIVE phase problems:
• Pelvis
• Passenger
• POWERS
PROBLEMS with INADEQUATE UTERINE CONTRACTIONS
Assessment of POWERS
Criteria for ADEQUACY of UTERINE CONTRACTIONS
• DURATION - 45-60 seconds
• FREQUENCY - every 2-3 minutes
• INTENSITY - > 50 mm Hg
How much can you change PROBLEMS with
INADEQUATE CONTRACTIONS?
How much can you change
PROBLEMS with INADEQUATE CONTRACTIONS?
Considerable!
Causes of ACTIVE phase problems:
• Pelvis
• Passenger
• POWERS
Causes of ACTIVE phase problems:
• Pelvis
• Passenger
• POWERS <- The only parameter that can be modified
Only CORRECTABLE Cause of ACTIVE phase problems:
Inadequate POWERS
IV OXYTOCIN
Diagnosis & Management
ACTIVE phase ARREST Findings:
• Cervical dilation > 3 cm with UCs present.
• NO Labor progress in multipara.
• NO Labor progress in primipara
Cause:
• Pelvic, Passenger, Powers.
Management:
• IV oxytocin (if inadequate UCs) or cesarean.
Diagnosis & Management
Prolonged ACTIVE phase Findings:
• Cervical dilation > 3 cm with UCs present.
• Labor progress <1.5 cm/hr in multipara.
• Labor progress <1.2 cm/hr in primipara
Cause:
• Pelvic, Passenger, Powers.
Management:
• IV oxytocin (if inadequate UCs) or cesarean.
Diagnosis & Management
ARREST of DESCENT Findings:
• Cervical dilation is 10 cm or “complete”.
• Delivery not take place in spite of adequate maternal pushing efforts.
• Duration > 30 min in multip or >60 min in primip.
Cause:
• Pelvic, Passenger, Powers.
Management:
• IV oxytocin, vacuum extractor, forceps or CS.
Intrapartum Fetal Monitoring
Case 13
• A 27 y/o primigravida at 41 wks gest is in labor in the maternity unit.
• She is 5 cm dilated, 100% effaced with UCs every 2-3 minutes.
• The EFM shows a baseline FHR of 140/min with decels: sudden drops of 40
beats/min lasting 15 seconds with rapid return.
ABNORMAL fetal monitor
Differential Diagnoses
ABNORMAL fetal monitor
• Early decelerations
• Variable decelerations
• Late decelerations
Diagnosis & Management
EARLY deceleration Findings:
• Onset of the deceleration is simultaneous with the onset of the contraction.
• End of the decelerations is simultaneous with the end of the contraction.
• Deceleration is a mirror image of the contraction.
Cause:
• Vagal stimulation; fetal head compression.
Management:
• Observation – no clinical significance.
Diagnosis & Management
VARIABLE deceleration Findings:
• Onset of the deceleration is variable with the onset of the contraction.
• End of the decelerations is variable with the end of the contraction.
• Sudden drops with rapid return to baseline.
Cause:
• Vagal stimulation; Umbil cord compression.
Management:
• Observation if mild-mod; worrisome if severe.
Diagnosis & Management
LATE deceleration
Findings:
• Onset of the deceleration is late in relation to the onset of the contraction.
• End of the decelerations is late in relation to the end of the contraction.
• Gradual drops with gradual return to baseline.
Cause:
• Uteroplacental insufficiency.
Management:
• All are worrisome!
Generic Interventions
ABNORMAL fetal monitor
• Decrease uterine activity
• Correct hypotension
• Change maternal position
• Administer high flow O2
• Vag exam r/o prolapsed cord
We have covered
The HIGHLIGHTS of
Obstetrics
USMLE Step 2
This brings us to
The END of the SESSION
BEST WISHES on the EXAM!