1968 – Commercially available 1972 – First scalp electrode 1970’s – Coins deceleration terms 1975 – 20 % of labors used EFM
EFM – Antepartum Testing Reactivity translates to a fetal death rate of < 5 /1000 Non-reactivity = fetal mortality rate of 40/1000 False positive rate 50-97(!) % Unless ominous, requires a confirmatory test
“Abnormal” “Predictive of abnormal acid-base status” Requires prompt intervention or delivery
MANAGEMENT OF Cat III Discontinued oxytocin Begin oxygen 5-6 L/min Correct maternal hypotension Trendelenberg position Increase IV fluids Vasopressor (ephedrine 15 mg IV) Assess maternal oxygenation and acid/base status Terbutaline 0.25 mg SQ for in-utero resuscitation
Lungs Heart Vasculature Uterus Placenta Cord Fetus Hypoxemia Hypoxia Metabolic acidosis acidemia Hypotension Environment Potential Injury Oxygen transfer Fetal response Oxygen transfer can be disrupted at any of these points and can manifest as FHR deceleration (variable, late, prolonged) The degree of oxygen disruption is the important factor, not the point in the pathway at which oxygen transfer is disrupted
DECREASED UTEROPLACENTAL OXYGEN TRANSFER TO THE FETUS Chemoreceptor Stimulus Alpha Adrenergic Response Fetal Hypertension Baroreceptor Stimulus Parasympathetic Response DecelerationDeceleration With Acidemia Without Acidemia Myocardial Depression
Category II “Everything that not categorized as either Category I or III” Examples : Tachycardia, bradycardia with normal variability Absent variability, marked variability Lates + variability, unusual variables
Category II FHR tracings are considered “indeterminate” Not predictive of abnormal fetal acid-base status but inadequate evidence to classify as Category I or III Requires evaluation and in-utero treatment if appropriate Requires continued surveillance and re-evaluation in context of clinical circumstances
Variability Moderate FHR variability is HIGHLY predictive of the absence of metabolic acidemia at the time it is observed Parer JT J Maternal Fetal Neonatal Med 2006; 19:289-94 Low JA Obstet Gynecol 1999; 93:285-91 Williams KP Am J Obstet Gynecol 2003; 188:820-3 Elimian A Obstet Gynecol 1997; 89:373-6
MINIMAL OR ABSENT FHR VARIABILITY CNS depressants: Narcotics, Barbiturates, Benzodiazapines, Sedatives, Alcohol Parasympatholytics: Phenothiazines, Atropine General anesthetics Magnesium sulfate Fetal tachycardia due to maternal fever or fetal infection Preexisting neurological injury Fetal acidosis/acidemia
NICHD 2008 - Pros Simple Better than 1998 More widely adopted ACOG buy-in
NICHD 2008 - Cons No evidence the system is actually better Lack of actionable recommendations Category II ?? Does not fix problems of EFM
A word about contractions Normal ≤ 5 contractions / 10 m Tachysystole ≥ 5 contractions / 10 m No hyperstimulation!
How About < 32 weeks? No clear recommendations < 28 weeks, 50 % will be non-reactive 28-34 weeks, 15 % “10 x 10”?
VAS? Artificial larynx used to stimulate the fetus Shortens time to reactivity 9.9 minutes 88 dB in the uterus Appears to be safe Reactive NST is just as reliable ?
What’s New? It’s clear we need something better Fetal Pulse-Oximetry STAN
Fetal Pulse Oximetry Same technology Oxygen saturation Mechanical problems
FPO – Cochrane Review 2007 5 trials 7424 subjects Overall no decrease in cesarean rate, seizures Fetal scalp sampling? East CE, Cochrane Database 2007
STAN ST Waveform Analysis Automated analysis of ST segments Uses EFM + ST FDA approved - 2005
2001 Lancet - STAN Sweden RCT 4966 subjects STAN vs EFM alone Decrease in acidosis [RR 0.47 0.25-0.81] Decrease in OVD [RR 0.83 0.69-0.99] Amer-Wehlin, Lancet 2001
2006 BJOG - STAN RCT 1493 subjects Similar design No difference in acidosis No difference in cesarean section or OVD Ojala K, BJOG 2006
STAN – Cochrane Review 2006 4 trials, 9829 subjects No difference in C/S, OVD Decreased acidosis [RR 0.64 0.41 – 0.99] Decreased HIE [RR 0.33 0.11-0.91] Insufficient evidence to recommend Neilson, JP Cochrane Database 2006