1 2009 Fetal Surveillance During Labor


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1 2009 Fetal Surveillance During Labor

  1. 1. Fetal Surveillance During Labor Du Xue , PHD Department of Obstetrics & Gynecology General Hospital of TianJin Medical University
  2. 2. Fetal Surveillance During Labor ---- Epidemiology <ul><li>To be an essential element of good obstetric care because intrapartum hypoxia and acidosis may develop in any pregnancy. </li></ul><ul><li>On the basis of prenatal care </li></ul><ul><li>----20% to 30% :high risk </li></ul><ul><li>----and 50% of perinatal morbidity and mortality occurs in this group </li></ul><ul><li>----50% normal </li></ul>
  3. 4. Mechanisms of fetal distress <ul><li>Fetal arterial blood oxygen tension is only 25±5mmHg compared with adult values of about 100 mmHg. </li></ul><ul><li>The rate of oxygen consumption is twice of the adult per unit weight, and its oxygen reserve is only enough to meet its metabolic needs for 1 to 2 minutes. </li></ul>
  4. 5. <ul><li>Blood flow from the maternal circulation is momentarily interrupted during a contraction. </li></ul><ul><li>Clinical and experimental data indicate that fetal death occurs when 50% or more of transplacental oxygen exchange is interrupted. </li></ul><ul><li>Hypoxia can easily occur. </li></ul><ul><li>A normal fetus can withstand the stress of labor without suffering from hypoxia because sufficient oxygen exchange occurs during the interval between contractions. </li></ul><ul><li>A fetus whose oxygen supply is marginal cannot tolerate the stress of contractions and will become hypoxic. </li></ul>
  5. 6. Changes under hypoxic conditions <ul><li>Baroreceptors and chemoreceptors in the central circulation of the fetus influent the FHR by giving rise to contraction-related or periodic FHR changes. </li></ul><ul><li>The hypoxia will also result in anaerobic metabolism. Pyruvate and lactic acid accumulate, causing fetal acidosis. </li></ul>
  6. 7. <ul><li>Methods of monitoring fetal heart rate </li></ul><ul><li>Meconium </li></ul><ul><li>Fetal blood sampling </li></ul><ul><li>Umbilical cord blood sampling </li></ul><ul><li>The Apgar scoring system </li></ul><ul><li>Nonstress test </li></ul><ul><li>Contraction stress test </li></ul><ul><li>Ultrasonic assessment </li></ul><ul><li>Biophysical profile testing </li></ul>Fetal Surveillance During Labor ----methods
  7. 8. Methods of monitorin fetal heart rate <ul><li>Auscultation of the fetal heart :by stethoscope or Doppler probe </li></ul><ul><li>Continuous Electronic fetal monitoring </li></ul><ul><li>External monitoring </li></ul><ul><li>Internal monitoring </li></ul>
  8. 9. <ul><li>Auscultation of the fetal heart is performed every 15 minutes after a uterine contraction during the first stage of labor. </li></ul><ul><li>Auscultation of the fetal heart is performed at least every 5 minutes after a uterine contraction during the second stage of labor. </li></ul><ul><li>By continuous electronic fetal monitoring , early recognition of changes in heart rate patterns </li></ul><ul><li>that may be associated with such fetal conditions as hypoxia and umbilical cord compression </li></ul><ul><li>would serves as a warning and enable the physician to intervene to prevent fetal death in uterus or irreversible brain injury. </li></ul>
  9. 10. Methods of Electronic Fetal Monitoring <ul><li>External </li></ul><ul><ul><li>Noninvasive method </li></ul></ul><ul><ul><li>Utilizes an ultrasonic transducer to monitor the fetal heart </li></ul></ul><ul><ul><li>Utilizes the tocodynamometer (toco) to monitor uterine contraction pattern </li></ul></ul><ul><ul><li>Application directly impacts results of data received </li></ul></ul>
  10. 11. Methods of Electronic Fetal Monitoring <ul><li>Internal Fetal Monitoring </li></ul><ul><ul><li>Invasive </li></ul></ul><ul><ul><li>FHR is monitored via a fetal scalp electrode (IFSE) </li></ul></ul><ul><ul><li>Uterine activity is monitored by an intrauterine pressure catheter (IUPC) </li></ul></ul><ul><li>A combination of external and internal fetal monitoring is common practice </li></ul>
  11. 12. <ul><li>continuous reporting of FHR-UC on a two-channel strip chart recorderby means of a monitor that prints results </li></ul><ul><li>----uterine contractions(UC): stress for the fetus </li></ul><ul><li>----FHR: alteration in FHR correlates with fetal oxygenation </li></ul><ul><li>In the clinical setting, internal and external techniques are often combined </li></ul><ul><li>----FHR: by using a scalp electrode for precise heart rate recording </li></ul><ul><li>----UC:the external tocotransducer for contractions to avoid or minimize possible side effects from invasive internal monitoring </li></ul>Electronic fetal monitoring
  12. 13. Fetal Heart Rate Patterns <ul><li>Baseline Assessment </li></ul><ul><li>Periodic Fetal Heart Rate Changes related to UC </li></ul>
  13. 14. Fetal Heart Rate Patterns Basline Assessment <ul><li>Fetal Heart Rate (in beats per minute) </li></ul><120 Bradycardia >160 Tachycardia 120-160 normal Beats/min Rate
  14. 15. Fetal Heart Rate Patterns Basline Assessment <ul><li>Baseline variability </li></ul><ul><ul><li>Short-time variability /beat-to-beat variability : short-term variability reflects the interval between either successive fetal electrocardiogram signals or mechanical events of the cardiac cycle </li></ul></ul><ul><ul><li>Long-term variability :Long-term variability reflects the frequency and amplitude of change in the baseline rate </li></ul></ul>
  15. 16. Short-time variability beat-to-beat variability Long-term variability
  16. 17. Short-time variability /beat-to beat variability <ul><li>Normal short-time variability fluctuates between 5 and 25 bpm </li></ul><ul><li>Variability below 5 bpm is considered to be potentially abnormal </li></ul><ul><li>When associated with decelerations a variability of less than 5 beats/minutes usually indicates severe fetal distress </li></ul>
  17. 18. Long-term variability <ul><li>The normal long-term variability is 3 to 10 cycles per minute. </li></ul><ul><li>Variability is physiologically decreased during the state of quiet sleep of the fetus,which usually lasts for about 25 minutes until transition occurs to another state. </li></ul>
  18. 19. Fetal Heart Rate Patterns Periodic Fetal Heart Rate Changes Three kinds of responses to uterine contractions <ul><ul><li>No change : The FHR maintains the same characteristics as in the preceding baseline FHR. </li></ul></ul>
  19. 20. Fetal Heart Rate Patterns Periodic Fetal Heart Rate Changes Three kinds of responses to uterine contractions <ul><ul><li>Acceleration : The FHR increases in response to uterine contractions. this is normal response. </li></ul></ul>
  20. 21. Fetal Heart Rate Patterns Periodic Fetal Heart Rate Changes Three kinds of responses to uterine contractions <ul><li>Deceleration : The FHR decreases in response to uterine contractions. Decelerations may be early, late, variable or mixed . All except early decelerations are abnormal. </li></ul>
  21. 22. Types of deceleration Patterns <ul><li>Early deceleration (head compression): </li></ul><ul><li>Late deceleration ( uteroplacental insufficiency </li></ul><ul><li>Variable deceleration (cord compression) </li></ul><ul><li>Combined or mixed patterns </li></ul><ul><li>Decreased beat-to-beat variability </li></ul>
  22. 23. Types of deceleration Patterns--1 Early deceleration :(head compression) <ul><li>Definition : The onset, maximum fall, and recovery that is coincident with the onset, peak, and end of the uterine contraction. </li></ul><ul><li>Significance : This pattern is seen when engagement of the fetal head has occurred. Early decelerations are not thought to be associated with fetal distress. </li></ul><ul><li>Mechanism : The pressure on the fetal head leads to increased intracranial pressure that elicits a vagal response </li></ul>
  23. 24. Types of deceleration Patterns--1 Early deceleration :(head compression)
  24. 25. Types of deceleration Patterns--1 Early deceleration :(head compression)
  25. 26. <ul><ul><li>Definition : </li></ul></ul><ul><ul><li>---onset </li></ul></ul><ul><ul><li>---maximal </li></ul></ul><ul><ul><li>---decrease </li></ul></ul><ul><ul><li>---recovery that is shifted to the right in relation to the contraction. </li></ul></ul>Types of deceleration Patterns--2 Late deceleration (uteroplacental insufficiency)
  26. 27. <ul><ul><li>Significance : </li></ul></ul><ul><ul><li>---The severity is graded by </li></ul></ul><ul><ul><li>the magnitude of the decrease </li></ul></ul><ul><ul><li>and the nadir of the deceleration </li></ul></ul><ul><ul><li>---Fetal hypoxia and acidosis </li></ul></ul><ul><ul><li>are usually more pronounced </li></ul></ul><ul><ul><li>with severe decelerations </li></ul></ul><ul><ul><li>---generally associated with low scalp blood PH values and high base deficits, indicating metabolic acidosis from anaerobic netabolism </li></ul></ul>Types of deceleration Patterns--2 Late deceleration (uteroplacental insufficiency)
  27. 28. Types of deceleration Patterns--3 Variable deceletation (cord compression) <ul><ul><li>Definition: This pattern has a variable time of onset and a variable form and may be nonrepetitive </li></ul></ul>
  28. 29. <ul><ul><li>Significance : </li></ul></ul><ul><ul><li>caused by umbilical cord compression. The severity is graded by their duration. </li></ul></ul>Types of deceleration Patterns—3 Variable deceletation (cord compression)
  29. 30. <ul><li>Partial or complete compression of the cord causes a sudden increase in blood pressure in the central circulation of the fetus. </li></ul><ul><li>The bradycardia is mediated via baroreceptors </li></ul><ul><li>Fetal blood gases indicate respiratory acidosis with a low PH and high CO 2. When cord compression has been prolonged, hypoxia is also present, showing a picture of combined respiratory and metabolic acidosis in fetal blood gases </li></ul>Types of deceleration Patterns—3 Variable deceletation (cord compression)
  30. 31. <ul><li>A flat baseline can be the result of several conditions: </li></ul><ul><ul><ul><li>Fetal acidosis </li></ul></ul></ul><ul><ul><ul><li>Quiet sleep state </li></ul></ul></ul><ul><ul><ul><li>Matermal sedation with drugs </li></ul></ul></ul>Types of deceleration Patterns—4 Decreased beat-to beat variability
  31. 32. Strategies for intervention--1 Attentions <ul><li>A normal FHR pattern on the electronic monitor indicates a greater than 95 % probability of fetal well-being </li></ul><ul><li>Abnormal patterns may occur, however, in the absence of fetal distress. The false-positive rate (i.e., good Apgar scores and normal fetal-acid-bade status in the presence of abnormal FHR patterns) is as high as 80 % </li></ul><ul><li>Electronic fetal monitoring is a screening rather than a diagnostic technique, because of the high false-positive rate </li></ul>
  32. 36. Have A Rest
  33. 37. <ul><li>the clinical circumstance </li></ul><ul><li>the maternal condition </li></ul><ul><li>the stage of labor </li></ul>Strategies for intervention--1 general considerations
  34. 38. <ul><li>A change in maternal position can relieves fetal pressure on the cord </li></ul><ul><li>100 % oxygen by face mask to the mother </li></ul><ul><li>Oxytocic infusion should be discontinued </li></ul><ul><li>Elevating the presenting part by vaginal examination </li></ul><ul><li>placing the mother in the trendelenburg position if the pattern is persistent </li></ul><ul><li>Use tocolytic agent to diminish uterine activity </li></ul>Strategies for intervention--2 Variable Decelerations
  35. 39. <ul><li>during the second stage of labor </li></ul><ul><li>aminioinfusion can decrease both the frequency and severity of variable decelerations </li></ul><ul><li>The benefit of aminioinfusion results in reduced cesarean deliveries for fetal distress and fewer low Apgar scores at birth without apparent maternal or fetal distress </li></ul>Strategies for intervention--2 Variable Decelerations
  36. 40. <ul><li>The safest intervention to deliver the fetus with cord compression is often low or outlet forceps. </li></ul><ul><li>When progressive acidosis occurs , as determined by serial scalp blood PH determinations, cesarean section should be performed if vaginal delivery is not imminent </li></ul><ul><li>Prolonged deceleration requires </li></ul><ul><li>immediate intervention (FHR </li></ul><ul><li>falls to 60 to 90 bpm for </li></ul><ul><li>more than 2 minutes) </li></ul>Strategies for intervention--2 Variable Decelerations
  37. 41. <ul><li>Need further evaluation because it may be assosiated with fetal acidosis </li></ul><ul><li>acoustic stimulation can be used to try to induce FHR-accelerations </li></ul><ul><li>A response of greater than 15 bpm lasting at least 15 seconds can ensures the absence of fetal acidosis </li></ul><ul><li>The chance of acidosis occurring in the fetus who fails to respond to such stimulation is about 50 % </li></ul>Strategies for intervention--3 Nonreactive fetal heart rate tracing
  38. 42. <ul><ul><li>Change the maternal position from supine to left or right lateral </li></ul></ul><ul><ul><li>Give oxygen by face mask, this can increase fetal Po 2 by 5 mmHg </li></ul></ul><ul><ul><li>Stop any oxytocic infusion </li></ul></ul><ul><ul><li>Inject intravenously a bolus of tocolytic drug to relieve uterine tetany. </li></ul></ul><ul><ul><li>Monitor maternal blood pressure </li></ul></ul><ul><ul><li>Operative delivery should be considered for fetal distress when fetal acidosis is present or when late decelerations are persistent in early labor and the cervix is insufficiently dilated </li></ul></ul>Strategies for intervention--4 Late Decelerations
  39. 43. <ul><li>Prolonged periods of tachycardia are usually associated with elevated maternal temperature or an intrauterine infection, which should be ruled out. </li></ul><ul><li>The acid-base status is usually normal </li></ul><ul><li>In general, fetal tachycardia occurs to improve placental circulation when the fetus is stressed. </li></ul><ul><li>Not a reliable change of the fetal distress </li></ul>Strategies for intervention--4 Fetal Tachycardia
  40. 45. Meconium <ul><li>The presence of meconium in the amniotic fluid may be a sign of fetal distress </li></ul><ul><li>Classification </li></ul><ul><li>----Early passage </li></ul><ul><li>----Late passge </li></ul><ul><li>----Management </li></ul>
  41. 46. Meconium ---- Early passage <ul><li>occurs any time prior to rupture of the membranes and is classified as light or heavy, based on its color and viscosity </li></ul><ul><li>light meconium : Light meconium is lightly stained yellow or greenish amniotic fluid. It is not associated with poor outcome </li></ul><ul><li>Heavy meconium : Heavy meconium is dark green or black and usually thick and tenacious. It is associated with lower 1- and 5- minute Apgar scores and is associated with the risk of meconium aspiration </li></ul>
  42. 47. Meconium ----Late passge <ul><li>Late passage usually occurs during the second stage of labor, after clear amniotic fluid has been noted earlier </li></ul><ul><li>Late passage, which is most often heavy, is usually associated with some event </li></ul><ul><li>----umbilical cord compression </li></ul><ul><li>----uterine hypertonus </li></ul><ul><li>----fetal distress. </li></ul>
  43. 48. Meconium ---- Management <ul><li>Amnioinfusion: it can decrease in meconium-related respiratory complications perhaps as a result of the dilutional effect of the infused fluid </li></ul><ul><li>Manner: </li></ul><ul><ul><li>Infuse a bolus of up of up to 800 ml of normal saline at a rate of 10-15 ml/minute over a period of 50 to 80 minutes. This is followed by a maintenance dose of 3 ml/minutes until delivery </li></ul></ul><ul><ul><li>Overdistention of the uterine cavity can be avoided by maitaining the baseline uterine tone in the normal range and at less than 20mmHg </li></ul></ul>
  44. 49. Fetal Blood Sampling PH :7.25-7.30 <ul><li>Indication : </li></ul><ul><li>clinical parameters </li></ul><ul><li>suggesting fetal distress: </li></ul><ul><li>----heavy meconium </li></ul><ul><li>----moderate to severely abnomal FHR patterns </li></ul><ul><li>Fetal Blood PH predicts neonatal outcome 82% of the time , as measured by the Apgar score. </li></ul><ul><li>The false-positive nate is about 8%, and the false-negative about 10% </li></ul>
  45. 50. Umbilical cord blood sampling <ul><li>If there have been problems during the delivery or concern with the infant’s condition,obtain an umbilical atery blood specimen for PH and acid-base determination is a syringe flushed with heparin. </li></ul><ul><li>If a specimen cannot be obtained from the umbilical artery ,obtain a specimen from an atery on the chorionic surface of the placenta. </li></ul>
  46. 52. Ultrasonic Doppler velocimetry <ul><li>For blood flow measurements in umbilical and fetal blood vessels, and percutaneous umbilical bolld sampling (PUBS) have been used antepartum but are generally not feasible methods for labor management. </li></ul><ul><li>Attention: Newborn cerebral dysfunction, manifested as seizures and attributable to true birth asphyxia, does not seem to occur unless the Apgar score at 5 minutes is 3 or less, the umbilical artery blood PH is less than 7,and resuscitation is necessary at birth. </li></ul>
  47. 53. The Apgar scoring system <ul><li>The Apgar score is an excellent tool for assessing the overall status of the newborn soon after birth (1 minute) and after a 5 minutes period of observation. </li></ul><ul><li>A normal Apgar score is 7 or greater at 1minute and 9 or 10 at 5 minutes. </li></ul><ul><li>Conditions result in low scores include </li></ul><ul><ul><li>Asphyxia (implies hypoxia of sufficient degree to cause metabolic acidosis) </li></ul></ul><ul><ul><li>Prematurity </li></ul></ul><ul><ul><li>maternal drug administration </li></ul></ul>
  48. 55. Questions <ul><li>The methods of monitoring the fetal heart rate </li></ul><ul><li>Fetal heart rate patterns </li></ul><ul><li>Classification of meconium </li></ul><ul><li>Normal level of fetal blood PH </li></ul>