Antepartum fetal monitoring

Question 1

What is the rate of fetal death antepartum and intrapartum and the etiologies?

Answer 1

Antepartum 80%, Intrapartum 20%
Etiologies: Chronic asphyxia, FGR, posterior, anomalies, complications (abruption, infection, Rh disease)

Question 2

What is the RR of stillbirth for a GA of 42 weeks

Answer 2

RR 12x risk of fetal death

Question 3

Fetal movements

Answer 3

• Fetal Movements
  o 30 movements / hour
  o Peaks at 2100 – 0100
  o Active states average 40 minutes
  o Inactive states average 20 minutes (75 min threshold)
  o Increased with maternal HYPOglycemia
  o Maternal glucose does not increase fetal activity
  o Fetal movements decrease in proportion to hypoxemia
• Decreased fetal movement
  o 60X RR of IUFD
  o Fetal movement does not decrease before delivery
• Fetal movement counting:
  o Less than 10 in 2 hours is 5SD below median
  o Median time to 10 movements is 21 minutes
  o 10 in 2 rule

Question 4

Breathing movements

Answer 4

o Begins as early as 10 weeks
o Present 30% of time in last 10 weeks of pregnancy
o Affected by:
 Time of day, glucose, hypoxemia, gestational age, etc

Question 5

CST definition and rate of cesarean delivery with positive CST

Answer 5

o Response to 3 contractions in 10 minute window
o Contraindications: PTL, previa, abruption, incompetent cervix
o Negative = absence of late decelerations in 10 minute window
o Positive CST = C/S rate 60%

Question 5

CST definition and rate of cesarean delivery with positive CST

Question 6

NST

Answer 6

o Hypoxia results in uncoupling of the FHR response to fetal movements
o Normal fetus may demonstrate lack of FHR accelerations for up to 80 minutes (fetal state F1)
o Low false negative rate
o FHR affected by CNS depressants, beta blockers, and smoking
o Reactive NST:
 2 FHR accels in 10-20 min; high NPV
o Manual stimulation and maternal glucose administration have no effect
o 24-28 weeks – 50% non-reactive
o NR NST:
 Persistent > 80 min requeirs BPP or CST
o FAS: sound 90-110 dB in utero; shorter testing time; comparable to spontaneously reactive NST
 Over fetal head with 3 separate stimuli 1 min apart
o Variable FHR:
 Abnormal cord position, oligo, Rh disease, placental compression, unknown

Question 7

UA Dopplers is the only test in RCTs that showed:

Answer 7

 Reduced perinatal mortality
 Reduced antenatal admissions
 Inductions of labor
 Cesarean section for fetal distress

Question 8

What are the venous dopplers and what do they show?

Answer 8

o DV, IVC, umbilical vein
o Venous Doppler abnormalities antedate FHR and BPP changes by days to weeks; may be better indicator of delivery timing that standard modes of fetal surveillance
o UV has triphasic wave form
 A wave: atrial contraction
 Backward flow during atrial contraction = abnormal