扬州大学：《妇产科学》课程教学课件（PPT讲稿）17 胎儿监护 Fetal Surveillance During Labor 1/3

Fetal Surveillancee During Labor

Fetal Surveillance During Labor

Contents in this classEpidemiology and Etiology of fetal distressMethods of monitoring fetal heart rateFetalheart ratepatternsStrategies for interventionMeconiumFetal blood samplingUmbilical cord blood samplingThe Apgar scoring systemNonstress testContractionstresstestUltrasonicassessmentBiophysical profile testing (BPS)

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（BPS）

EpidemiologyFetal surveillance during labor is an essentialelement of good obstetric care because of thefact that intrapartum hypoxia and avidosismay develop in any pregnancy.On the basis of antepartum maternal history,physical examination, and laboratory data,20% to 30% of pregnancies may bedesignated high risk ,and 50% of perinatalmorbidity and mortality occurs in this group

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

UterineconditionsTetanicUmbilical cordcontractions,conditionsHyperstimulationOneartery,Vasa previa,Hematoma,Shortcord,True knot,FetalconditionsNuchal cordAnemia,ProlapseInfarction.Twin-twinPlacentaltransfusionconditionsInfarctionAbruption,PostmatureplacentaMaternalconditionsHypertension,Hypotension,Severe anemia,Cardiacdisease,Seizures,Pulmonary diseaseFigure 10-2. Clinical conditions associated with fetal distress in labor

Mechanisms of fetal distress100Fetal arterial blood oxygentension is only 25±5mmHg80compared with adult values ofFETUSMOTHERabout 100 mmHg60The rate of oxygen4consumption is twice of theadult per unit weight, and its20oxygen reserve is only enoughto meet its metabolic needs200406080100for 1 to 2 minutes.PO,mm Hg

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

Uterine ArteryUmbilicalArteryP0,=100mmHgPo,=18mmHgBlood flow from the maternalCOz=15.2ml/dlCo,=8.0mldcirculation is momentarilySao2=95%Sao,=40%Pco, =32mm.HgPco,=55mmHginterrupted during aPH=7.42PH=7.21BE=-3.0mEqLBE=-9.0mEqLcontraction,Clinical and experimentaldataindicatethat fetaldeathoccurswhen50%ormoreofUterine blood fiowUmbilical blood fiow.transplacentaloxygen700ml/min500ml/minHb concentration:Hbconcentration:exchange is interrupted.12gm/d15gm/dlOxygen capacity.Oxygen capacity.16ml/dl2Hypoxia can easily occur.22mlldl(Total Qo,through(TotalQog,3.5kguterus:fetus:Anormalfetuscan withstand3.5ml/min)2.0ml/min)the stress of labor withoutsuffering from hypoxia becausesufficient oxygen exchangeUterine VeinUmbilical Veinoccurs during the intervalPo2=33mmHgPoz=28mmHgbetween contractions.CO,=10.5mldlCo,=15.0mldlSao,=60%Sao,=70%AfetuswhoseoxygensupplyisPoo,=40mmHgPcoz=45mmHgpH=7.30pH=7.32marginal cannot toleratetheBE#-6.0mEqLBE=-6.4mEqLstress of contractions and willFigure71Placentaltransferfoxygenandcarbondioxide.AdaptedfromBonicalbecome hypoxic.ObsttricAnagiaandnthsianddmterdamWodedrationfSocietiesAnesthesiologists,1980,p29

◼ 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

Changes under hypoxicconditionsBaroreceptors 压力感受器 and chemoreceptors inthe central circulation of the fetusinfluence the FHR by giving rise tocontraction-related or periodic FHRchanges.The hypoxia will also result in anaerobic厌氧的 metabolism. Pyruvate 丙酮酸盐 and lactic acidaccumulate, causing fetal acidosis

Changes under hypoxic conditions ◼ Baroreceptors 压力感受器 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 厌氧 的 metabolism. Pyruvate 丙酮酸盐 and lactic acid accumulate, causing fetal acidosis

Methods of monitoring fetal heart rateStraingaugeTranscervicalAuscultation 所诊 of thintrauterinepressureFetalmonitoringsystemcatheterfetal heart:bystethoscope orDopplerprobeDContinuousElectronicfetalHeartIntrauterineratepressuremonitoringExternal monitoringInternal monitoringScalpelectrodeFigure10-1.Techniqueforcontinuous electronicmonitoringoffetalheartrateandpressure of uterine contractions

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

Benificial points for Internalmonitoring"than “External one"Internal monitoring gives better FHR tracingsbecause the rate is computed from the sharplydefined R-wave peaks of the fetalelectrocardiogram.While in external monitoring,the rate is computed from the less preciselydefined first heart sound obtained with anultrasonictransducer.The internal uterine catheter allows precisemeasurement of the intensity of thecontractions in millimeters of merecury.Theexternal tocotranducer measures onlyfreguency and duration, not intensity

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

Auscultation of the fetal heart is performedevery 15 minutes after a uterine contractionduring the first stage of labor.Auscultation of the fetal heart is performedat least every 5 minutes after a uterinecontraction during the second stage of labor.By continuous electronic fetal monitoring,early recognition of changes in heart ratepatterns that may be associated with suchfetal conditions as hypoxia and umbilicalcord compression would serves as a warningand enable the physician to intervence toprevent fetal death in uterus or irrevessiblebrain injury

◼ 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