Antepartum testing


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Lecture for Basic Fetal Monitoring

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Antepartum testing

  2. 2. Antepartum Fetal Assessment Fetal movement counting Antepartum fetal heart rate testing Biophysical profile Doppler velocimetry
  3. 3. Which test to use? Nonstress test Biophysical profile, modified biophysical profile Contraction stress test Low incidence of unexpected fetal death Increase in time, cost and inconvenience Doppler velocimetry
  4. 4. Fetal Movement - Advantages Is a daily assessment Easy and Non-invasive Requires no special equipment Mom becomes more in tune with fetus and morelikely to recognize changes in behavior
  5. 5. Fetal Movement Counting
  6. 6. Purpose of NST Determine if: Inadequate delivery of oxygen and/or nutrition infetal tissue Inadequate placenta exchange due to decreasedblood flow, decreased surface area or increasedmembrane thickness. Inadequate maternal nutrients or oxygen to theplacenta
  7. 7. Nonstress Test (NST) FHR accelerations reflect CNS alertness and activity(fetal well being) Absence of FHR accelerations may reflect CNSdepression caused by hypoxia, drugs, fetal sleep, orcongenital anomalies. The endpoint of the NST is the presence orabsence of FHR accelerations within a specifiedperiod of time
  8. 8. Performing the NST Position patient in semi-fowler or left lateral tilt (tominimize supine hypotension) Apply external monitors for contraction and FHRmeasurement Mark tracing when fetal movement is felt or heard Fetal sound stimulation may be used to elicit a response.
  9. 9. Nonstress Test (NST) Accelerations of the FHR occur with fetalmovement, uterine contractions, or in response toexternal stimuli.
  10. 10. Nonstress Test (NST) Target criteria is 2 accelerations of at least 15 beatsper minute (BPM) for 15 seconds in a 20-minuteperiod A healthy fetus < 32 weeks’ gestation may use atleast 2 accelerations of 10 beats per minute (BPM)for 10 seconds in a 20-minute period The more remote from term, the more likely thatnonreactivity will be due to fetal prematurity.
  11. 11. Interpreting the NST Reactive: Presence of at least 2 accelerations in a 20minute period Non reactive: FHR does not accelerate to meetcriteria or the fetus does not move May extend the testing period to 40 minutes or perform aback-up test. Reactive or Nonreactive with decelerations:individualize management
  12. 12. Biophysical Profile (BPP) Biophysical activities that can be recordedwith real time ultrasound: Fetal movement (FM) Fetal tone (FT) Fetal breathing movements (FB) Amniotic fluid volume (AFV, also known as AFI)
  13. 13. Biophysical Profile (BPP) Assessment of umbilical blood flow providesinformation on blood perfusion of thefetoplacental unit. Activities that become active first in fetaldevelopment (FT, FM) are the last to disappearwhen asphyxia arrests all activities. Activities that become active later in gestation(NST, FBM) will be abolished 1stin cases ofhypoxia and acidosis.
  14. 14. Biophysical Profile (BPP) - Scoring Each assessment When normal: 2 When abnormal: 0 Highest Score: 10, Lowest Score: 0 Accuracy improved by increasing the number ofvariables assessed. Overall false negative rate: 0.6/1000
  15. 15. Biophysical Profile (BPP) - Scoring NST: reactive – as described earlier. FBM: present - at least 1 episode of at least 30seconds duration (within a 30 minute period). FM: present - at least 3 discrete episodes. FT: normal - at least 1 episode of extension ofextremities or spine with return to flexion. AFV: normal – largest pocket of fluid greaterthan 1 cm in vertical diameter.
  16. 16. Purpose of Contraction Stress Test A hypoxic fetus will manifest late decelerationswhen uterine blood flow is compromised Late decelerations correlate with stillbirth, IUGR,and low Apgar scores.
  17. 17. Contraindications to CST PROM Previous classical cesarean delivery Placenta previa Incompetent cervix History of premature labor in this pregnancy Multiple gestation
  18. 18. Performing the CST Uterine contractions in excess of 30 mm Hgcreate an intrauterine pressure that temporarilystops uterine blood flow. A well oxygenated fetus has reserve to toleratecontractions Contractions for CST can be achieved through: Oxytocin challenge test (OCT) Breast (nipple) stimulation
  19. 19. Interpretation of the CST Negative: no late decelerations and adequate FHRrecording Positive: Late decelerations present with themajority of contractions (without excessiveuterine activity) Equivocal test results: Suspicious,hyperstimulation, unsatisfactory.
  20. 20. Doppler Flow Studies In Normal conditions the placenta offers littleresistance to fetal and maternal blood flow, evenduring diastole (i.e., between heart beats) Useful in evaluation and management of pregnanciescomplicated by conditions such as Suspected fetal growth restriction Red blood cell isoimmunization Pre-eclampsia
  21. 21. Doppler Flow Studies The most commonly assessed Doppler flowstudy of the fetus is the umbilical arterySystolic flowDiastolic flowNormal blood flow
  22. 22. Doppler Flow Studies Waveform may show decreased/absent diastolicblood flow in the umbilical vessels of a fetus Decreased/absent blood flow indicates that thefetus may not be receiving enough blood,nutrients, and oxygen from the placentaSystolic flow No endDiastolic flow
  23. 23. QUESTIONS?