OB Lecture 3 - NON–INVASIVE ANTEPARTUM FETAL SURVEILLANCE USTMED ’07 Sec C - AsM Antepartum Fetal Surveillance Definition - All methods to monitor fetal well being before labor Administered : 1. age of gestation when fetal survival possible 2. When neuro developmental center is already operative Antepartum Fetal Surveillance Methods Non-Invasive Invasive Fetal Movement Counting Amniocenteses Non-Stress Test Chorionic Villus Sampling Contraction Stress Test Fetal Blood Sampling Biophysical Profile Scoring Doppler Velocimetry
Non- Stress Test Basis : Fetus with good integration of PNS, SC , brain and autonomic NS and intact myocardium will respond to FM with accelerations -
Reactive – 2 FM in 20 min. , FHR accels. 15 bpm.,15 secs. , variability 6bpm. N baseline
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Non-Reactive – (-) FM, (-) acceleration w/ movement or stimulation, poor or (-)LTV, baseline N or abn. Uncertain Reactivity - < 2 FM in 20 min. or accels of < 15 bpm.,<15 secs., LTV < 6 bpm. Abn. Baseline
Basis :
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Fetal Movement Counting Simple Least Expensive Second half of pregnancy -
Interpretation:
Compromised fetus ↓ O2 requirements by reducing activity ( + ) correlation between maternal perception of fetal movements and movements by US scanning for 28-43 wks. Documented cessation of fetal activity warns of impending death
Method: Most attractive and convenient “ count to 10” Performed at any convenient time Patient Left lateral , concentrate on fetal activity Evening hours, recent meal not necessary Father help in charting promote family attachment and compliance
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Fetal Kick Count Chart Contact physician if >1 hr to feel 10 movements
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Limitations of Fetal Movement Counting 1. Patient Comprehension and Convenience Clear instructions mandatory Educational attainment and socioeconomic background Problem of compliance before advent of “ Count to 10 method” 2. Failure to anticipate certain stillbirths: No technique can anticipate stillbirths When FMC reassuring , still births may be due to acute hypoxic changes (abruptio placenta, umbilical cord compression) 3. Failure to detect growth abnormalities: Diminished activity only in the most severe cases of IUGR < 5h percentile ( Matthew,1975) 4. Failure to detect malformations: Most fetuses w/ congenital anomalies show normal fetal movement patterns
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Fetuses w/CNS anomalies (hydrocephalus) or restriction of the LE (congenital hip dysplasia) ↓ FM (Rayburn, 1985) Failure to distinguish bet multiple pregnancies: Technique cannot distinguish between twins on daily basis. Mother cannot determine which of the fetuses are less active. Drugs
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Depressant drugs: barbiturates, benzodiazepines, narcotics, methadone, alcohol ↓ FM
Reactive
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Non-reactive
Reactive Test - good fetal well being for 1 week or more in > 99% of cases. Non- Reactive Test – poor fetal outcome (perinatal death, Low 5 min. AS, late decels.) in < 20 % cases
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Uncertain Reactivity- repeat NST, back-up BPS, CST depending on clinical condition or OB judgement.
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Limitations of NST 1. Fetal Sleep State Fetal sleep state affects fetal cardioregulatory center, periodic variation in variability Periods of quiet sleep last for 1 hr. extend observation time to eliminate possibility of fetal sleep state OFFSET LIMITATION “10-20-40” rule Extension to 90 min. improve false (+) rate Fetal inactivity may be prolonged up to 1 hr. 2.
DRUGS Increase FHR Mechanism B-adrenergic stimulation Increase Metabolic rate CNS stimulants Vagal Blockade Paracatechol Stimulants A-adrenergic blockade
Example Ritodrine Terbulatline Isoxuprine Caffeine, Thyroxine Cocaine, Ketamine Atropine Ephedrine Phentolamine
Decrease FHR Mechanisms Vagal Stimulation/SA Myocardial depressants B-sympathetic blockade CNS depressants
Example Digoxin Lidocaine Propanolol General anesthetics
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Day2 of Bethamethasone administration FM ↓ 49% all values return to normal Day4 transient effect Smoking:
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Temporary ↓ in FM Because of increased maternal carboxyhemoglobin levels or direct effect of nicotine on Fetal CNS
Electronic Fetal Heart Rate Monitoring
Maternal Conditions: Thyrotoxicosis , Hypokalemia – baseline FHR variability Maternal dehydration - ↑ FHR
Maternal fever - ↑ fetal core temp.; ↑ FHR Fetal Conditions: Congenital Anomalies –heart block, anencephaly Gestational Age: “Physiologic non-reactivity” NST in preterm infant : 15bpm amplitude not typical < of organized fetal arousal states (state F) common quiet sleep states (state 1F)
Low amplitude decelerations seen with FM
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FHR ↓ in both rest and activity periods with↑ in AOG Extend testing time and modifying criteria to 10 bpm/accelerations reduce False (+) rate of NST. NICHD ,1997 Research Guidelines for Interpretation of FHR: < 32 weeks –accelerations in preterm fetus is >/= 10 bpm. , >/= 10 secs. Poor predictor of chronic asphyxia: non- visualization of Amniotic Fluid must be combined with BPS or AFV measurement Clinical Efficacy of NST
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FM (movement) FB (breathing) FHR (heart rate)
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Non-Reactive Test FURTHER EVALUATION (BPS , CST)
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Methodology: Same with NST , 20 min. recording of FHR and uterine activity. (-) Uterine contractions : 1. IV Oxytocin 3 cxns. In 10 mins. 2. Nipple stimulation ( cost-effective , shorter testing time. 1 nipple x 2 min. , rest 5 min.
Variable Fetal Breathing
Interpretation of CST
Fetal Movements
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Negative – (-) Late decelerations or significant variable decelerations Positive – Late decelerations ff. by 50% or > if frequency is < 3 in 10 min. Equivocal Suspicious – Intermittent late or significant VD present in one contraction Equivocal Hyperstimulatory – FHR decels. in cxns. > 2 min. or > 90 secs. Unsatisfactory - < 3 cxns. In 10 min. or uninterpretable trace
Fetal Heart Rate AFV
8/10 N AF 8/8
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Limitations of CST Same limitations as NST Limited application : Multiple Pregnancy Preterm Labor Hx. Of Uterine Rupture Placental Abnormalities Classical CS scar
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(+) CST poor predictive value < 35% Management depend on: 1. age of gestation – Preterm , BACK-UP BPS or Doppler. Term or Post term DELIVER 2. Maternal Condition
Biophysical Profile Scoring Basis: Hypoxia Cascade Fetal CNS centers FT Cortex/subcortical (tone) area
Embryogenesis
7.5-8.5 wks
Score 0 < 30 sec. Of fetal breathing movements in 30 mins. 2 or < gross body movements in 30 min. observation Semi or full limb extension w/ no return or slow return to flexion (-) accelerations or < 2 Of FHR in 20 min. AF pocket < 1 cm. In 2 planes
Management (-) indication for delivery weekly testing DM 2 x a week (-) indication for delivery Rpt. Test /protocol DELIVER AF abn. DELIVER <36 wks. N AF Cx favorable Deliver, if < 36 wks. LS ration<2 ,Cx unfavorable , rpt.test in 24 hrs. , rpt. Test < Deliver >6 Observe Rpt.test same day < 6 deliver DELIVER
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Modifications in BPS Selective use of NST when all other 4 variables are normal Substitution of AFI for vertical pocket NST/AFI – complete BPS for abn. NST or AFV BPS & Placental Grade – scoring 3 for intermediate variable VAS
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Timing and Frequency of BPS
Test Reliability of CST
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Interpretation Normal Nonasphyxiated Normal Nonasphyxiated Chronic fetal asphyxia suspect Possible fetal asphyxia
Possible fetal asphyxia Almost certain asphyxia
0 to 2
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Amniotic Fluid Volume
BPS Interpretation
BPS Score 10
6
CST (-)
Hypoxia
requires a period of time before alterations become visible Amniotic Fluid Volume – Fetal compensatory mechanism Blood flow directed to essential organs (Brain, Heart, Adrenals) non-essential organ (Kidney)
Score 2 30 sec. Sustained Breathing Movements In 30 min. 3 or > Gross Body Movements in 30 min. Simultaneous limb and Trunk movements 1 episode of motion of a limb fr. Position of flexion to ext. w/ return FHR accels 15/bpm. Lasting for 15 secs. W/ FM for 20 min. AF pocket 1 cm. In 2 planes
8/10 ↓ AF
CST (+)
20-21 wks 24 wks
Methodology: curvilinear scanner Initial survey: a. Fetal #,lie ,position b. Placenta c. Fetal morphometric data ( BPD,AC,FL) d. Gen. Survey Fetal Tone, Fetal Movement, Breathing, AFV combined with NST for Full BPS , (-) NST Modified Biophysical Profile Scoring
Fetal Tone
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4th ventricle Post. Hypothalamus medulla
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9 wks
Two categories: 1. Acute biophysical variables: altered immediately in the presence of fetal hypoxemia FB, FT,FM, HEART RATE (NST) 2. Chronic Biophysical Variables:
High False (+) Rate 80%
Contraction Stress Test Basis: Marginally compromised fetus w/ limited O2 reserve and limited placental function manifest w/ late decelerations when subjected to uterine contractions.
Cortex-nuclei
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Time and frequency variable Individualized approach “ Disease specific testing “ Testing not started at AOG where active intervention not possible More immature fetus more abnormal score to warrant delivery Take into consideration maturation of CNS centers
Limitations of BPS 1. Fetal rest activity cycles: Fetus variation in sleep states average 20-30 min. more pronounced with fetal maturity REM stage – FB present 30-75% of time, apnea pds. brief, GBM more frequent, FT diminished
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Maternal Glucose level:
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Non- REM –FB 14- 35% ,apnea pds. long so that if < 30 min. observation of absent FB may not be due to hypoxia FT increased, GBM diminished
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The average interval between last normal score and fetal death was 3.62 days (placental & cord accidents)
Doppler Velocimetry
↑ incidence of FB after meals.
↑ in FB in the 2nd. & 3rd hr. after a 800kcal. Meal during the last10 wks. of pregnancy No association with meals and incidence of GBM and FT. Gestational Age:
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FB seems to ↑ with advancing AOG 24-28 wks. –14% of time , 19 wks- 6%, 10 wks- 2% GBM & FT – move more often at earlier AOG , more sporadic and shorter Alcohol and Smoking: FB– inhibited by alcohol , 20 oz. Of alcohol in healthy pregnant women inhibit FBM x 3hrs not reversed by glucose Smoking –controversial
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Doppler Shift
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2 cigarettes ↓ FB ↓ in rate but not incidence Nicotine – effect on uterine vasculature causing fetal hypoxemia, direct effect on fetal respiratory drive GBM & FT – not affected by Smoking and Alcohol
Spectral analysis: 1. Quantification of flow – unreliable 2. Doppler wave form analysis – waveform from an arterial source represent arterial velocity waveform and is configured by upstream and downstream circulatory factors.
Labor:
FB – initial fall in the rate with Braxton Hicks cxns. With ↑ after
incidence ↓ during last 3 days prior to onset of labor and during latent phase, abolished during active phase GBM & FT – no effect
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Drugs ↓ FBM Anesthetics halothane, thiopental Barbiturates Narcotics – morphine Benzodiazepines Prostaglandin Pancuronium
↑ FBM Cathecolamines adrenalin, B mimetics Adenylcyclase inhibitors Prostaglandin synthetase inhibitors –indomethacin Doxapram
Drugs – Fetal Movement Drug Effect Inhalational anesthetics Abolition of FM (Halothane) Neuromuscular Blocking Abolition of FM Agents (pancoronium) Narcotics Reduced FM Neuroepileptics Variable effect Steroids Transient decrease Drugs – Effect on FT Drug Effect Neuromuscular Blocking Agents ↓ in flexor tone Phenobarbital & Benzodiazepines ↓ in flexor tone Narcotics to the mother (-) effect 7.
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Polyhydramnios Maternal Diseases w/ polyhydramnios (DM, Multiple Pregnancy, Hydrops) cannot be assessed because no score,only in oligohydramnios Inability to provide an estimate of fetal reserve
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Waxing and waning of BPS parameters in sustained hypoxemia indistinguishable fr. N BPS activities. This is because of fetal compensation & resetting of sensitivity. Sudden insult (abruptio), superimposition of 2nd insult ( uterine cxns.)
Wave Form Analysis Arterial Umbilical MCA Uterine Aorta Renal Artery Internal Carotid Artery
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Other Coronary sinus Coronary arteries Pulmonary artery
Limitations of Doppler Velocimetry 1. Use as a primary antepartum surveillance test limited ( IUGR, DM,SLE, APAS ) o ALERT signal of possibility of fetal compromise associated with placental pathology o Utilize other tests ( BPS, NST, CST) o Beginning of a spectrum NOT a pt. Where morbidity appears o Mean duration of Dx. Of AEDV to onset of fetal distress 6-8 days 2 High quality equipment and trained personnel 3 Inability to predict stillbirths related to acute changes in maternal fetal status (placental and cord accidents)
4 Drugs: Drug Terbutaline & Ritodrine MgSO4 Steroids: Dexamethasone Betamethasone
Effect ↓ S/D ratio UA, Uterine Artery ↓ MCA indices ↓ PI in MCA
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Interpretation and Management Guidelines o Umbilical Artery Doppler weekly o Abn. Doppler studies useful in determining frequency of other tests o Abn. Doppler studies < 32 weeks look for other evidences of fetal compromise o > 32 weeks, prior to term deteriorating Doppler studies (AEDV, REDF) may be indication for delivery. o *** Take into consideration ALL clinical factors
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Umbilical Artery
Test Reliability:
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Venous Ductus Venosus Inferior Vena Cava
Corrected Perinatal Mortality Rate: 0 – 26.4/1000 False (-) rate : 0.078-2.28
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CT Significant ↓ in CS for fetal distress (-) effect on perinatal mortality
Umbilical Artery Flows
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Cochrane Pregnancy and Childbirth Group, 2002 11 RCT’s N = 7000 HR with doppler vs. HR w/o Doppler Results:
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↓ perinatal deaths (OR .71, 95%CI 0.50 – 1.01) fewer induction of labor (OR .83 95% CI .74-. 93) • fewer hospital admissions (OR .56 95% CI .43 -.72) Conclusion: Use of umbilical doppler in HR pregnancies improve outcome and reduce perinatal deaths •
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Conclusion 1. Methods and Limitations 2. NO tests superior 3. INTEGRATE whole clinical picture !!
- fin AsM