1. Fetal Surveillance During Labor Zhangxiulan, PHD Department of Gynecology and Obstetrics,Gerneral Hospital, TianJin

2. Contents in this class Epidemiology and Etiology of fetal distress Methods of monitoring fetal heart rate Fetal heart rate patterns Strategies for intervention Meconium Fetal blood sampling Umbilical cord blood sampling The Apgar scoring system Nonstress test Contraction stress test Ultrasonic assessment Biophysical profile testing

3. Epidemiology Fetal surveillance during labor is an essential element of good obstetric care because of the fact that intrapartum hypoxia and avidosis may develop in any pregnancy. On the basis of antepartum maternal history, physical examination, and laboratory data, 20% to 30% of pregnancies may be designated high risk,and 50% of perinatal morbidity and mortality occurs in this group.

5. Mechanisms of fetal distress Fetal arterial blood oxygen tension is only 25±5mmHg compared with adult values of about 100 mmHg. 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.

6. Blood flow from the maternal circulation is momentarily interrupted during a contraction. Clinical and experimental data indicate that fetal death occurs when 50% or more of transplacental oxygen exchange is interrupted. Hypoxia can easily occur. A normal fetus can withstand the stress of labor without suffering from hypoxia because sufficient oxygen exchange occurs during the interval between contractions. A fetus whose oxygen supply is marginal cannot tolerate the stress of contractions and will become hypoxic.

7. Changes under hypoxic conditions Baroreceptors and chemoreceptors in the central circulation of the fetus influence the FHR by giving rise to contraction- related or periodic FHR changes. The hypoxia will also result in anaerobic metabolism. Pyruvate and lactic acid accumulate, causing fetal acidosis.

8. Methods of monitoring fetal heart rate Auscultation of the fetal heart:by stethoscope or Doppler probe Continuous Electronic fetal monitoring External monitoring Internal monitoring

9. Benificial points for “ Internal monitoring ” than “ External one ” Internal monitoring gives better FHR tracings because the rate is computed from the sharply defined R-wave peaks of the fetal electrocardiogram.While in external monitoring, the rate is computed from the less precisely defined first heart sound obtained with an ultrasonic transducer. The internal uterine catheter allows precise measurement of the intensity of the contractions in millimeters of merecury. The external tocotranducer measures only frequency and duration, not intensity.

10. Auscultation of the fetal heart is performed every 15 minutes after a uterine contraction during the first stage of labor. Auscultation of the fetal heart is performed at least every 5 minutes after a uterine contraction during the second stage of labor. By continuous electronic fetal monitoring, early recognition of changes in heart rate patterns that may be associated with such fetal conditions as hypoxia and umbilical cord compression would serves as a warning and enable the physician to intervence to prevent fetal death in uterus or irrevessible brain injury.

11. Electronic fetal monitoring allows continuous reporting of the FHR and uterine contractions(FHR-UC) by means of a monitor that prints results on a two-channel strip chart recorder. Uterine contractions represent a stress for the fetus, and the alteration in FHR correlates with fetal oxygenation. In the clinical setting, internal and external techniques are often combined by using a scalp electrode for precise heart rate recording and the external tocotransducer for contractions to avoid or minimize possible side effects from invasive internal monitoring.

12. Fetal Heart Rate Patterns Basline Assessment Periodic Fetal Heart Rate Changes

13. Fetal Heart Rate Patterns Basline Assessment Rate Beats/min normal 120-160 abnormal Tachycardia >160 Bradycardia <120 Fetal Heary Rate (in beats per minute)(see table 10-1)

14. Fetal Heart Rate Patterns Basline Assessment Baseline variability 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 Long-term variability :Long-term variability reflects the frequency and amplitude of change in the baseline rate

16. Short-time variability /beat-to beat variability Normal short-time variability fluctuates between 5 and 25 bpm Variability below 5 bpm is considered to be potentially abnormal When associated with decelerations a variability of less than 5 beats/minutes usually indicates severe fetal distress

17. Long-term variability The normal long-term variability is 3 to10 cycles per minute. 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.

18. Fetal Heart Rate Patterns Periodic Fetal Heart Rate Changes Three kinds of responses to uterine contractions No change: The FHR maintains the same characteristics as in the preceding baseline FHR.

19. Fetal Heart Rate Patterns Periodic Fetal Heart Rate Changes Three kinds of responses to uterine contractions Acceleration: The FHR increases in response to uterine contractions. this is normal response.

20. Fetal Heart Rate Patterns Periodic Fetal Heart Rate Changes Three kinds of responses to uterine contractions Deceleration: The FHR decreases in response to uterine contractions. Decelerations may be early, late, variable or mixed. All except early decelerations are abnormal.

21. Types of Patterns Early deceleration (head compression): Late deceleration ( uteroplacental insufficiency Variable deceleration (cord compression) Combined or mixed patterns Decreased beat-to-beat variability

22. Early deceleration (head compression) Definition: The onset, maximum fall, and recovery that is coincident with the onset, peak, and of the uterine contraction. Significance: This pattern is seen when engagement of the fetal head has occurred. Early decelerations are not thought to be associated with fetal distrss. Mechanism: The pressure on the fetal head leads to increased intracranial pressure that elicits a vagal response similar to the valsalva maneuver in the adult.

23. Late deceleration (uteroplacental insufficiency) Definition: The onset, maximal decrease, and recovery that is shifted to the right in relation to the contraction. Significance: The severity of late decelerations is graded by the magnitude of the decrease in FHR an the nadir of he deceleration. Fetal hypoxia and acidosis are usually more pronounced with severe decelerations. Mechanism:Late decelerations are generally associated with low scalp blood PH values and high base deficits, indicating metabolic acidosis from anaerobic netabolism

24. Mechanism of Late decelerations The degree of fetal acidosis can be measured by sampling blood from the presenting part. The PH of fetal scalp blood normally varies between 7.25 and 7.30.Values below 7.20 are considered to be abnormal but not necessarily indicative of fetal compromise Late decelerations are generally associated with low scalp blood PH values and high base deficits, indicating metabolic acidosis from anaerobic netabolism The patial pressure of carbon dioxide (Pco 2 ) in the fetal blood is usually in the normal range, and the fetal blood oxygen partial pressure (Po 2 ) is only slightly below normal because of the Bohr effect-the shift to the left of the oxygen dissociation curve caused by the acidosis

25. Variable deceletation (cord compression) Definition: This pattern has a variable time of onset and a variable form and may be nonrepetitive Significance: Variable decelerations are caused by umbilical cord compression. The severity of variable decelerations is graded by their duration. when the FHR falls below 80 beats/minute during the nadir for the deceleration, there is usually a loss of P-wave in the fetal electrocardiogram, indicating a nodal rhythm or a second-degree heart block

26. Variable deceletation (cord compression) Machanism Partial or complete compression of the cord causes a sudden increase in blood pressure in the central circulation of the fetus. The bradycardia is mediated via baroreceptors 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

27. Decreased beat-to beat variability A flatbaseline can be the result of several conditions: Fetal acidosis Quiet sleep state Matermal sedation with drugs

28. Attentions: A normal FHR pattern on the electronic monitor indicates a greater than 95% probability of fetal well-being 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 % Electronic fetal monitoring is a screening rather than a diagnostic technique, because of the high false-positive rate

33. Strategies for intervention as general rules Depend on the clinical circumstance Depend on the maternal condition Depend on the stage of labor

34. Variable Decelerations A change in maternal position to the right or left side generally relieves fetal pressure on the cord and abolishes the decelarations 100% oxygen should be given by face mask to the mother Oxytocic infusion should be discontinued Elevating the presenting part by vaginal examination or placing the mother in the trendelenburg position if the pattern is persistent Use tocolytic agent to diminish uterine activity When severe degree of variable deceleration are seen during the second stage of labor, aminioinfusion can decrease both the frequency and severity of variable decelerations.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

35. Variable Decelerations The safest intervention to deliver the fetus with cord compression is often low or outlet forceps. Attention: the condition is in the second stage of labor, and the cervix must be fully dilated, membranes ruptured, and the fetal head engaged into the pelvis. The bladder should be emptied. If progress of the fetal head is not obtained with appropriate traction, cephalo pelvic disproportion should be suspected and the procedure should be abandoned in favor of a cesarean section When progressive acidosis occurs, as determined by serial scalp blood PH determinations, cesarean section should be performed if vaginal delivery is not imminent When the FHR falls to 60 to 90 bpm for more than 2 minutes, it requires immediate intervention, too.

36. Nonreactive fetal heart rate tracing Placing an artificial larynx with 120 dB of sound on the maternal abdomen in the vicinity of the vertex, acoustic stimulation can be used to try to induce FHR- accelerations A response of greater than 15 bpm lasting at least 15 seconds can ensures the absence of fetal acidosis The chance of acidosis occurring in the fetus who fails to respond to such stimulation is about 50%

37. Late Decelerations Change the maternal position from supine to left or right lateral Give oxygen by face mask, this can increase fetal Po 2 by 5 mmHg Stop any oxytocic infusion Inject intravenously a bolus of tocolytic drug to relieve uterine tetary. Monitor maternal blood pressure 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

38. Fetal Tachycardia Prolonged periods of tachycardia are usually associated with elevated maternal temperature or an intrauterine infection, which should be ruled out. The acid-base status is usually normal In general, fetal tachycardia occurs to improve placental circulation when the fetus is stressed.

40. Meconium The presence of meconium in the amniotic fluid may be a sign of fetal distress Early passage Late passge Management

41. Early passage Early passage occurs any time prior to rupture of the membranes and is classified as light or heavy, based on its color and viscosity A. light meconium: Light meconium is lightly stained yellow or greenish amniotic fluid. It is not associated with poor outcome B. 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

42. Late passge Late passage usually occurs during the second stage of labor, after clear amniotic fluid has been noted earlier Late passage, which is most often heavy, is usually associated with some event, e.g: umbilical cord compression or uterine hypertonus, late in labor that causes fetal distress.

43. Management Amnioinfusion: it can decrease in meconium-related respiratory complications perhaps as a result of the dilutional effect of the infused fluid Manner: 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 Overdistention of the uterine cavity can be avoided by maitaining the baseline uterine tone in the normal range and at less than 20mmHg

44. Fetal Blood Sampling Manner: Blood is obtained from the fetus by placing an amnioscope transvaginally against the fetal skull. Cervical mucus is removed with cotton swabs. Silicone grease is applied to the skull for blood bead formation. A 2Х2- mm lancet is used for a stab incision, and a drop of blood is aspirated into a long heparinized glass capillary tube Fetal blood PH correctly predicts neonatal outcome 82% of the time, as measured by the Apgar score. The false-positive nate is about 8 %, and the false-negative about 10%

45. Umbilical cord blood sampling If there have been problems during the delivery or concern with the infant ’ s condition,obtain an umbilical atery blood sqecimen for PH and acid-base determination is a syringe flushed with heparin. If a specimen cannot be obtained from the umbilical artery,obtain a specimen from an atery on the chorionic surface of the placenta.

47. Ultrasonic Doppler velocimetry 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. 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 resuseitation is necessary at birth.

48. The Apgar scoring system The Apgar score is an excellent tool for assesing the overall status of the newborn soon after birth (1 minute) and after a 5 minutes period of observation. A normal Apgar score is 7 or greater at 1minute and 9 or 10 at 5 minutes. Conditions result in low scores include Asphyxia (implies hypoxia of sufficient degree to cause metabolic acidosis) Prematurity maternal drug administration

50. Nonstress test Left lateral supine position,20 minutes 2 fetal motion Fetal heart beat response to fetal motion (degree and time) 15 fetal heart rate acceleration for at least 15 senconds. Basic fetal heart beat Basic Fetal heart beat variation

51. Contraction stress test Uteroplacental function The diluted oxytocin is infused to induce the uterine contraction at least 3 times in 10 minutes. Uterine contraction leading to the uteroplacental perfusion decreased, to examine the fetal tolerance to the transient ischemia or transient hypoxia. The positive: each contraction with a late deceleration The suspicious: only one deceleration is observed.

52. Real-time Ultrasonography To determine the adequacy of amniotic fluid volume Fetal breathing and fetal movements

53. Ultrasonic assessment The amniotic fluid index (AFI) is represents the total of the linear measurements in centimeter of the largest amniotic fluid pockets noted on the ultrasonic inspection of each of the four quadrants of the gestational sac. Oligohydramnios: AFI less than 5 Polyhydramnios: AFI more than 23 Fetal breathing and fetal movements (30 breathing movements in 10 minutes and 3 body movements in 10 minutes) Placenta maturation (calcification)

54. Biophysical profile testing NST Amniotic fluid Muscle movement Respiratory movement Fetal tone

55. THANKS FOR YOUR ATTENDANCE GOOD LUCK