Antepartum Fetal Testing

Antepartum Fetal Testing: Examining the Evidence
Presentation lecture by:Jay J Bringman, MD
University of Tennessee Health Sciences Center, Memphis

Objectives
* Understand physiology behind antepartum fetal testing
* Review evidence for antepartum fetal testing
* Indications for testing
* Review what test to use
* What to do with an abnormal test
* When to start and the frequency in which to test

Cerebral Palsy
* Case-control study of term infants weighing >2500g in Australia
* Case: neonate with diagnosed moderate or severe neonatal encephalopathy in first week of life
* Control: term neonate without diagnosis of neonatal encephalopathy
* Evaluated role of preconceptional, antepartum and intrapartum factors in neonatal encephalopathy
* Strongest antepartum risk factor for NE is IUGR; OR 38.2 (9.4-154.8)
* Other risk factors:

Physiologic basis for antenatal testing
* Fetal testing designed to assess for fetal hypoxia

Non-stress test physiology
* Afferent signals:
* When stimulated, send afferent impulses to brain to increase FHR
* Efferent signals increase FHR
* If movement and accelerations observed, reasonable to conclude the afferent and efferent limbs intact and cardioregulatory neurons adequately oxygenated

NST: How to do it
* Patient in lateral tilt position
* Tracing observed for 40 minutes
* Accelerations peak (but do not necessarily remain) at least 15 BPM above baseline
* Last for 15 seconds
* Reactive: 2 or more accelerations within 20 m period
* Nonreactive: one that lacks sufficient accelerations over 40 minute period
* No contraindications

The preterm fetus
* Frequently nonreactive
Evidence for use of NST
Randomized trials
Caveats
NST versus VAS
NST and nonrandomized data
Caveat for observational data
Contraction stress test
CST interpretation
Biophysical profile
What score tells you…

* Normal acute variables and AFI
* Normal pH and blood gases secondary to compensation
* Abnormal blood gases and normal AFI
* Abnormal acute and abnormal blood gases
* Goal is to recognize asphyxia and deliver prior to morbidity and mortality

Cesarean delivery
IOL for abnormal testing
Induction of labor
Nonrandomized data
Biophysical profile
Fetal movement assessment
Indications for antepartum monitoring
Maternal and Fetal Indications
Which test to use?
* Most evidence points to use of NST as first line test
* Imperative to remember that it should not be used a sole test
* Other tests should be used in situation of nonreassuring testing such as BPP or CST
* NST can be used in conjunction with Doppler studies in IUGR

What to do if test is abnormal?
* True false-positive test results not known
o Test introduced without rigorous evaluation of utility
* Abnormal result in context of clinical situation
o Did maternal condition change?
o Abnormal test usually followed by other test
+ 90% of NRNSTs followed by negative CST
o If NRNST followed by positive CST, delivery warranted in morphologically normal fetus

Abnormal BPP
When to start?
How frequently?

Antepartum Fetal Testing.ppt