INTRAPARTUM ASSESSMENT Ch. 14. INTRAPARTUM ASSESSMENT 부산백병원 산부인과 R1 손영실

INDEX 1. Periodic Fetal Heart Rate 2. Amnioinfusion 3. Second-stage Labor FHR Patterns 4. Fetal Scalp Blood Sampling 5. Complications From Electronic Fetal Monitoring

PERIODIC FETAL HEART RATE - Deviations from baseline that are related to uterine contractions ① Acceleration - increase in FHR above baseline ② Deceleration - decrease below baseline rate - early, late or variable type - the waveform of these deceleration is also significant for pattern recognition

PERIODIC FETAL HEART RATE - slope of FHR change early and late deceleration ⇒ gradual, resulting in a curvilinear and uniform or symmetrical waveform variable deceleration ⇒ abrupt and erratic, giving the waveform a jagged appearance ◎ Another system (based on the pathophysiological cause) • type Ⅰ : early type ⇒ head compression • type Ⅱ : late type ⇒ uteroplacental insufficiency • type Ⅲ : variable type ⇒ cord compression pattern

PERIODIC FETAL HEART RATE 1) Acceleration - abrupt increase (defined as onset of acceleration to a peak in <30 seconds) in FHR baseline - occur most commonly antepartum, in early labor, and in association with variable decelerations - proposed mechanisms • fetal movement • stimulation by uterine contraction • umbilical cord occlusion • fetal stimulation during pelvic exam • fetal scalp blood sampling & acoustic stimulation - can occur during labor without any apparent stimulus

PERIODIC FETAL HEART RATE 2) Early deceleration - gradual decrease and return to baseline associated with a contraction • drop in a heart rate with uterine contractions • related to cervical dilatation • physiological - generally seen in active labor between 4~7 cm dilatation Features of early fetal heart rate deceleration. Characteristics include gradual decrease in the heart rate with both onset and recovery coincident with the onset and recovery of the contraction. The nadir of the deceleration is 30 seconds or more after the onset of the deceleration.

PERIODIC FETAL HEART RATE - not associated with fetal hypoxia, acidemia, or low Apgar scores - head compression probably cause vagal nerve activation due to dural stimulation ⇒ mediate HR deceleration

PERIODIC FETAL HEART RATE 3) Late deceleration - FHR response to uterine contractions : an index of either uterine perfusion or placental perfusion - a smooth, gradual symmetrical decrease in FHR beginning at or after the peak of the contraction and returning to baseline only after the contraction has ended - the magnitude is rarely more than 30~40 bpm below baseline and typically not more than 10~20 bpm in intensity - usually not accompanied by acceleration - maternal hypotension (m/c), excessive uterine activity, or placental dysfunction ⇒ induce late deceleration

PERIODIC FETAL HEART RATE

PERIODIC FETAL HEART RATE 4) Variable deceleration - most common deceleration pattern encountered during labor (d/t umbilical cord occlusion) • labor progressed to 5cm dilatation ⇒ 40% • the end of 1st stage ⇒ 83% Features of variable fetal heart rate decelerations. Characteristics include abrupt decrease in the heart rate with onset commonly varying with successive contractions. The decelerations measure ≥ 15 bpm for 15 seconds or longer with an onset to nadir phase of less than 30 seconds. Total duration is less than 2 minutes.

PERIODIC FETAL HEART RATE ◎ two type of variable deceleration • A : seen with complete umbilical cord occlusion • B : different configuration because of the “shoulders” of acceleration before and after the deceleration component - the variation of variable decelerations was caused by differing degrees of partial cord occlusion Varying (variable) fetal heart rate decelerations. Deceleration B exhibits “shoulders” of acceleration compared with deceleration A.

PERIODIC FETAL HEART RATE ◎ physiological scheme ① only vein occlusion ⇒ reduce fetal blood return ⇒ triggering a baroreceptor -mediated acceleration ② subsequent complete occlusion ⇒ umbilical artery flow obstruction ⇒ result in fetal systemic hypertension ⇒ baroreceptor-mediated deceleration

PERIODIC FETAL HEART RATE ◎ significant variable deceleration decreasing to less than 70 bpm lasting more than 60 seconds ⇒ pathological ◎ saltatory baseline HR - rapidly recurring couplets of acceleration and deceleration causing relatively large oscillations of baseline FHR - related to cord occlusion - in the absence of other FHR finding, these do not signal fetal compromise

PERIODIC FETAL HEART RATE 5) Prolonged deceleration - isolated decelerations lasting 2 minutes or longer - but less than 10 minutes from onset to return - difficult to interpret (d/t many different clinical situations) - more common cause ① cervical exam ② uterine hyperactivity ③ cord entrapment ④ maternal supine hypotension - others : epidural, spinal analgesia, maternal hypoperfusion or hypoxia, placental abruption, umbilical knots or prolapse, maternal seizure, impending birth, maternal valsalva maneuver

PERIODIC FETAL HEART RATE - fetus may die during prolonged deceleration - thus, management can be extremely tenuous

AMNIOINFUSION ◎ infused saline through the intrauterine pressure catheter in laboring women who had either variable decelerations or prolonged deceleration attributed to cord entrapment ⇒ such therapy improved the heart rate pattern in half ◎ clinical areas of transvaginal amnioinfusion ① treatment of variable or prolonged decelerations ② prophylactically in cases of known oligohydramnios, as with prolonged rupture of membranes ③ in an attempt to dilute or wash out thick meconium ◎ protocol - 500~800 ml bolus warmed normal saline followed by a continuous infusion of approximately 3 ml/hr

AMNIOINFUSION Complication Centers Reporting No. (%) Uterine hypertonus 27 (14) Abnormal fetal heart rate tracing 17 (9) Amnionitis 7 (4) Cord prolapse 5 (2) Uterine rupture 4 (2) Maternal cardiac or respiratory compromise 3 (2) Placental abruption 2 (1) Maternal death [ Complications Associated with Amnioinfusion from a Survey of 186 Obstetrical Centers ]

SECOND-STAGE LABOR FHR PATTERNS ◎ only 1.4% of over 7,000 deliveries did not have FHR deceleration during 2nd stage labor (by Melchior & Bernard, 1985) ◎ both cord compression and fetal head compression have been implicated to cause decelerations and bradycardia during 2nd stage labor ◎ loss of beat-to-beat variability and baseline FHR less than 90 bpm were predictive of fetal acidemia

FETAL SCALP BLOOD SAMPLING ◎ measurement of the pH in capillary scalp blood ⇒ help to identify the fetus in serious distress ◎ procedure ① an illuminated endoscope is inserted through the dilated cervix after ruptured membranes so as to press firmly against the fetal scalp ② skin is wiped clean with a cotton swab and coated with a silicon gel ③ an incision is made through the skin to a 2mm depth with a special blade on a long handle ④ as a drop of blood forms on the surface, it is immediately collected into a heparinized glass capillary tube, and the pH of the blood is promptly measured

FETAL SCALP BLOOD SAMPLING ◎ protocol to try to confirm fetal distress ① pH > 7.25 ⇒ labor is observed ② 7.20 < pH < 7.25 ⇒ the pH measurement is repeated within 30 minutes ③ pH < 7.20 ⇒ another scalp blood sample is collected immediately mother is taken to an operating room and prepared for surgery delivery is performed promptly if the low pH is confirmed

FETAL SCALP BLOOD SAMPLING

ELECTRONIC FETAL MONITORING COMPLICATIONS FROM ELECTRONIC FETAL MONITORING ① injury to the fetal scalp or breech by the electrode - rarely a major problem - the eye in case of face presentation ⇒ serious ② fetal vessel in placenta may be ruptured by catheter ③ penetration of the placenta ④ uterine perforation ⑤ infection

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