Summary NUR 350 OB Exam 4 Study Guide

OB Exam 4 Study Guide
Ch. 26: Assessment of High-Risk Pregnancies
 Antepartum Testing:
o Labs:
 Indirect Coombs:
 When: during pregnancy (28 weeks)
 Why: test for maternal antibodies that could harm baby
 How: maternal blood during pregnancy
 Treatment?: Rhogam for mother if indicated
 Parameters to monitor: if titer > 1:8, do amnio to
check bili levels in amniotic fluid (titer also determines
severity of fetal hemolytic anemia)
 Direct Coombs:
 When: immediately after birth
 Why: determine if NB blood contains antibodies against
maternal O blood (1st infants can be affected by ABO
incompatibility)
 How: blood draw from newborn’s umbilical cord
 Treatment?: if titer is high (hyperbili), start
phototherapy
 Parameters to monitor: titer level indicates degree of
sensitization
 Percutaneous Umbilical Blood Sampling:
 When: second, third trimesters
 Why: to detect fetal anemia, infection,
thrombocytopenia, fetal mutations
 How: uses ultrasound to guide needle through
abdomen and retrieve blood sample from umbilical cord
 Treatment?: depends on outcome
 Parameters to monitor: depends on suspected
outcome
o MRI
 When: any point during pregnancy
 Why: evaluate fetal structures, overall growth, placenta,
quantity of amniotic fluid, gestational trophoblastic disease
 How: no contrast medium used
 Treatment?: N/A

, Parameters to monitor: fetal CNS, thorax, abdomen, GU,
musculoskeletal system, placental position and density
o Contraction Stress Test (Oxytocin test)
When: second, third trimesters

Why: earlier warning of fetal compromise than NST

How: oxytocin infusion to cause contractions

Treatment?: further evaluation may be required

Parameters to monitor: negative result (ideal)= no late or

variable decels
o Non-Stress Test
 When: second/third trimesters
 Why: monitor fetal wellbeing
 How: EFM—uses toco and ultrasound
 Treatment?: nonreactive result requires further monitoring
 Parameters to monitor: reactive= baseline of 110-160, no
decels and at least 2 accels
 Ultrasonography
o For nuchal translucency
When: 10-14 weeks
Why: identify possible fetal abnormalities
How: ultrasound
Treatment?: N/A
Parameters to monitor: fluid collection > 3mm is abnormal
and can indicate chromosomal abnormalities; trisomy 21
markers include absent nasal bone, shortened femur -/+
humerus, echogenic bowel, pyelectasis, brady/tachycardia
o Ultrasound
 When: transvaginal—1st trimester; abdominal—after 1st
trimester
 Why: transvaginal—ectopic pregnancy, monitor early on and
establish age, identify abnormalities; abdominal—standard
reveals presentation, fluid volume, cardiac activity, placental
position, number of fetuses; limited determines fetal
presentation during labor and fluid volume; specialized is
used if abnormalities are suspected or otherwise indicated
 How: transvaginal—probe inserted into vagina; abdominal—
over abdomen and displaces uterus upward to better view the
fetus, requires full bladder

, Treatment?: N/A

Parameters to monitor: fetus position, anatomical

markers/abnormalities
o Doppler studies
 When: second/third trimesters
 Why: monitor blood flow and indicate fetal
adaptation/reserve
 How: noninvasive ultrasound
 Treatment?: N/A
 Parameters to monitor: severe restriction to blood flow can
indicate IUGR
 Biophysical Profile
 When: second and third trimesters
 Why: assess physical characteristics of fetus, response to
stimuli (5 categories, 2 points each)
 How: ultrasound
 Treatment?: N/A
 Parameters to monitor: amniotic fluid, fetal breathing,
movements, tone, and reactivity/heart rate (with NST) (each
worth 2 points)
 Modified BPP: shorted version, combines NST with AFV;
ideal is reactive NST with deepest vertical pocket >2cm
 Prenatal Screening
o Amniotic Fluid Volume Index (AFV/I)
When: second/third trimesters

Why: evaluate amount of amniotic fluid; oligo=congenital

anomalies (Potter Syndrome, PROM), poly=GI and CNS
abnormalities, multi fetuses, fetal hydrops
 How: ultrasound around maternal umbilicus to determine
vertical depths of largest amniotic fluid pocket
 Treatment?: depends on outcome
 Parameters to monitor: oligohydramnios=<1-2cm
(index=<5cm), polyhydramnios=>8cm (index= ≥ 25cm)
o Amniocentesis
 When: after 14 weeks
 Why: genetic disorders that may harm mom/fetus; neural
tube defects

,  How: needle is used to obtain amniotic fluid and study the
fetal cells
 Treatment?: depends
 Parameters to monitor: depends
o Chorionic Villus Sampling
 When: 10-13 weeks
 Why: can provide earlier diagnosis and rapid results to
 How: ultrasound guides a biopsy catheter into placenta to
collect tissue specimen
 Treatment?: N/A
 Parameters to monitor: depends
o Assay screens
 Alpha feto protein (MSAFP)
 When: done between 15-20 weeks (*ideally, 16-18
weeks)
 Why: screen for neural tube defects (spina bifida,
anencephaly)
 How: uses maternal blood
 Treatment?: depends on defect
 Parameters to monitor: depends
 First trimester screening (triple screen)
 When: between 11-14 weeks
 Why: can provide early detection for trisomy 21
 How: maternal blood
 Treatment?: N/A
 Parameters to monitor: two maternal biochemical
markers—PAPP-A (pregnancy-associated plasma protein
A) and hCG (human chorionic gonadotropin) + these
results in conjunction with fetal NT
 Second trimester screening (quad screen)
 When: between 15-21 weeks
 Why: can detect trisomy 21 and 18
 How: maternal blood
 Treatment?: N/A
 Parameters to monitor: MSAFP, hCG, inhibin,
unconjugated estriol
o 21: lower MSAFP and estriol, elevated hCG and
inhibin