Obstetrics Flashcards
How is pregnancy confirmed in a patient with amenorrhea, enlargement of the uterus, and positive urinary b-HcG?
1) Presence of gestational sac (seen via transvaginal US at 4-5 weeks)
2) Presence of yolk sac (visualized w/in gestational sac at 4-6 weeks)
3) Fetal heart motion (seen by US at 5-6 weeks)
What is the mnemonic that should be used to describe parity?
TPAL
T:term (>37wks)
P: preterm (20-36+6 weeks)
A: abortions (<20 wks)
L: living children
What are the routine screening tests for first trimester pregnancy?
CBC (for anemia, bld d/o’s)
Blood type, Rh, antibody screening (type and screen; direct/indirect Coombs)
Genitourinary screening (PAP smear, UA/culture)
Immunization status (rubella Ab, hep b surface Ag)
Infection (Hep C Ab, VDRL/RPR, HIV assay, cervical cx for gonorrhea/chlamydia)
What are the optional screenings in the first trimester?
Tuberculosis (QFT gold or PPD)
Trisomy 21 early testing (B-hcg, pregnancy-associated plasma protein A, fetal nuchal translucency, cell-free DNA)
What is the most common cause of anemia in pregnancy?
Iron deficiency
What are the cutoffs for anemia in pregnancy?
1st or 3rd trimester: <11
2nd trimester: <10.5
What are the next steps in management for anemia detected on screening?
low hemoglobin, low MCV: give iron, test for thalassemia if anemia does not improve
low hemoglobin, high MCV, high RDW: give folate
What’s the next step in management for thrombocytopenia detected in pregnancy screenings?
If <150K, correlate clinically for ITP
What is the significance of Rh-negative mothers? What’s the next step?
May become sensitized (anti-D Ab) which increases the risk of erythroblastosis fetalis in subsequent pregnancies
Give RhoGAM to Rh-neg mothers at 28wks after first rescreening for absence of anti-D antibodies
Give RhoGAM to Rh-negative mothers after any procedure and after delivery
What is the role of direct/indirect Coombs tests in first trimester screening?
Detects atypical RBC Abs
How do you manage asymptomatic bacteriuria in pregnant women?
ALWAYS treat ASB in pregnancy to prevent pyelonephritis (30% risk when untreated)
- cephalosporins, amoxicillin
- you need a test of cure *
What is the implication of negative rubella antibodies in first trimester pregnancy?
Increased risk of primary rubella infection
- do NOT give rubella immunization during pregnancy, wait til after delivery
What is the implication of positive Hep B surface antigen in first trimester pregnancy?
Indicates risk for vertical transmission of HBV
- order HVB e-antigen
- positive HBV e-Ag indicates highly infectious state
What is the implication of a positive HCV antibody during first trimester pregnancy?
Will change delivery management to reduce likelihood of vertical transmission
- avoid amniotomy, prolonged rupture of membranes, and placement of fetal scalp electrode at time of delivery
treat between pregnancies
What are the implications of positive tests for syphilis in first trimester pregnancy?
Confirm w/ treponemal-specific tests (MHATP or FTA)
- if positive, treat w/ IM penicillin
What are the implications of positive HIV testing in first trimester pregnancy?
Perform HIV-1/HIV-2 antibody differentiation immunoassay, +/- plasma HIV RNA level
- all babies born to HIV+ women will be HIV Ab+ thru passive transport of maternal Abs and do not indicate infection
- triple antiretroviral therapy
- zidovudine in labor; C-section if viral load >1000
What are the changes to delivery protocol for HIV+ women?
Zidovudine in labor
C-section if viral load >1000
What is the first choice of treatment for chlamydia/gonorrhea in first trimester pregnancy?
PO azithromycin + IM ceftriaxone
What is the treatment for bacterial vaginitis in pregnant women?
PO or vaginal metronidazole or clindamycin
What do you do when a pregnant woman has a positive QFT or PPD?
CXR to r/o active disease
(-) CXR: INH and rifapentine if tx initiated prior to pregnancy; otherwise, can defer til after delivery
(+) CXR (+) sputum: begin triple therapy antituberculosis tx
** avoid streptomycin due to ototoxicity
How is a positive trisomy 21 screening test confirmed?
Chorionic villus sampling or amniocentesis
What are the second trimester optional tests? (testing window 15-20wks)
Quadruple Marker Screen
- MS-AFP
- beta-HCG
- Estriol
- Inhibin A
What is the significance of elevated MS-AFP in second trimester quadscreen?
Possibly indicative of neural tube defect, ventral wall defect, twin pregnancy, placental bleeding, renal disease, sacrococcygeal teratoma, or teratoma
*all abnormal MS-AFPs should have US to confirm dating and then be repeated if gestational dating was wrong
What is the significance of low MS-AFP in second trimester quadscreen?
+low estriol, high beta-HCG, high inhibin A = Down Syndrome
(Hcg and Inhibin A are ‘HI’ in Down Syndrome)
+low estriol, low beta-HCG, low inhibin A = Edward syndrome
What is the most common cause of abnormal MS-AFP in second trimester quadscreen?
Gestational dating error
Accurate dating is essential for accurate interpretation
If gestational dating is confirmed via US, what is the next step for evaluating high or low MS-AFP on quadscreen?
HIGH: amniocentesis for AF-AFP level and acetylcholinesterase activity
- high amniotic fluid acetylcholinesterase activity is specific to open neural tube defect
LOW: amniocentesis for karyotyping
When is the optimal time to screen for gestational diabetes?
24-28 weeks when human chorionic somatomammotropin (HCS) secretion by the placenta is at its peak (peak suppression of maternal insulin sensitivity)
What are the routine third trimester screening tests?
- Diabetes (1hr 50g OGTT)
- Anemia (CBC at 24-28wks)
- Atypical antibodies (indirect Coombs test)
- GBS screening (vaginal and rectal culture for GBS at 36wks)
What are the indications of an abnormal 1hr glucose tolerance test >130-140 mg/dL in the third trimester?
Perform 3 hr 100g OGTT (definitive test for gestational diabetes); requires overnight fast
- positive if >2 elevated values
What is the significance of an abnormal CBC in the third trimester?
Hemoglobin <11g/dL = anemia
The most common cause is iron deficiency, even if it wasn’t present in the first trimester
- give Fe supplementation
What is the significance of an abnormal indirect Coombs test in the third trimester?
Performed in Rh-negative women to look for atypical antibodies (anti-D Ab) before giving RhoGAM
- not indicated in RH neg women who have already developed anti-D antibodies
What is the significance of a positive GBS in the third trimester?
High risk for sepsis in a newborn
- teat w/ intrapartum IV abx (penicillin G, clindamycin or erythromycin if allergic to penicillin and sensitivities available, vanc if sensitivities not available)
