Antenatal Testing

1
Antenatal Testing A Review of the current
Recommendations

• Sarah Waller, MD
• MFM Fellow
• Department of OB/GYN
• University of Washington Medical Center
• October 22, 2010

2
Objectives

• To review the background for the origin of
  antenatal testing
• Learn the appropriate response for test results
  based on procedures and policies established
• To learn the various indications and recommended
  surveillance for specific maternal and fetal
  conditions
• Evaluate the benefits of testing

3
Background

• In both animals and humans, fetal heart rate
  pattern, level of activity, and degree of
  muscular tone are sensitive to hypoxemia and
  acidemia
• Redistribution of fetal blood flow in response to
  hypoxemia may result in diminished renal
  perfusion and oligohydramnios

4
Background

• In humans, the range of normal umbilical blood
  gas parameters has been established by
  cordocentesis performed in pregnancies in which
  the fetus ultimately proved to be healthy, and
  ranges vary by gestational age
• Manning et al (1993)
• Fetuses with a non-reactive nonstress test (NST)
  were found to have a mean umbilical vein pH of
  7.28.
• Cessation of fetal movement appears to occur at
  lower pH levels fetuses with abnormal movement
  were found to have an umbilical vein pH of 7.16
  0.08

5
Etiology of Antenatal Deaths

• 33

• 66

• Unexplained

• Maternal
• Acute chorioamnionitis
• Diabetes mellitus
• Rheumatologic disorders
• Placental
• Abruption
• Large chorioangiomas
• Hypertensive disorders of pregnancy
• Fetal
• Structural defects
• Genetic syndromes
• Growth restriction

6
When and How often do Babies die?

• Fetal Deaths
• Incidence 6.2/1000 total births (2005)
• 25-75 of these may be avoided
• Early stillbirth 20-27 weeks per 1000 total
  births
• Late stillbirth 28 weeks per 1000 total births
• Neonatal Deaths
• Incidence 4.5 of all live births (2000)
• Early death lt7 days of life per 1000 total live
  births
• Late death 7-27 days of life per 1000 total live
  births

7
Etiology of Neonatal Deaths
Cause Percentage
Congenital malformations or chromosome abnormalities 20
Low birth weight or prematurity 17
Sudden infant death syndrome (SIDS) 7
Neonatal death due to maternal complications 6
Neonatal death from complications of the placenta, cord, or membranes 4
Unintentional injuries 4
8
NEED FOR ANTENATAL TESTING

• Adverse Perinatal Outcomes
• Cerebral Palsy 2/1000 live born infants
• Neonatal encephalopathy 1.9-3.8/1000 live births
  
• May result in permanent neurologic disability

9
UTEROPLACENTAL INSUFFICIENCY

• Implies an inadequate nutritive or respiratory
  supply to the fetus secondary to inadequate
  exchange between the maternal-fetal unit as a
  consequence of maternal, uteroplacental, or fetal
  disorders

10
What Tests areAvailable?
11
History of Fetal Monitoring
1980s Continuous fetal monitoring is widely used
in labor
12
Antepartum Testing

• Any test of fetal well-being typically has a low
  false-negative rate and a high false-positive rate

13
Antepartum Testing

• Electronic fetal monitoring
• Contraction stress test
• Nonstress test
• Ultrasound
• Fetal biometry
• Biophysical profile
• Amniotic fluid index
• Doppler velocimetry
• Maternal monitoring of fetal activity

14
Nonstress Test (NST)

• Reactive
• 2 accelerations within 20 min (may be extended to
  40 min)
• Nonreactive
• lt2 accelerations in 40 min
• False Negative 0.2-0.65
• False Positive 55-90

15
Advantages of a NST as compared to CST

• Faster
• Simpler
• Nursing not required
• Less expensive
• Easier to interpret
• No contraindications

16
Causes of a Nonreactive NST

• Fetal

• Maternal

• Hypoxia
• Sleep cycle
• CNS anomalies
• Cardiac anomalies

• Fever with fetal tachycardia
• Administration of narcotics or sedatives

17
Contraction Stress Test (CST)

• False Negative 0.04
• False Positive 35-65

18
Amniotic Fluid Volumes
19
Decreased Amniotic Fluid

• Uteroplacental insufficiency
• PROM
• Congenital anomalies
• Chromosomal abnormalities
• All are associated with adverse perinatal outcomes

20
Measurement of Amniotic Fluid

• Direct measurement
• Dye-dilution
• Aspiration at delivery
• Ultrasound
• Single deepest pocket
• Amniotic fluid index
• 2 x 2 cm pocket technique
• Subjective assessment

21
Assessment of Amniotic Fluid Measurement by U/S

• Sensitivity for detecting
• Normal fluid is high
• Oligohydramnios 10-25
• Polyhydramnios 30-45
• No technique is significantly better than another
  in predicting abnormal fluid or adverse outcome
• AFI is 2-3 times more likely to diagnose
  oligohydramnios and lead to intervention

22
Amniotic Fluid Assessment in Twins

• Use single deepest vertical pocket for each twin
• Membrane must be visible
• gt2cm is normal
• Subjective assessment is just as accurate

23
Biophysical Profile (BPP)

• Acute variables subject to immediate change
• Fetal muscle tone
• Fetal movements
• Fetal breathing
• Fetal reactivity
• Chronic variable - take several days to change
• Amniotic fluid level

24
Biophysical Profile (BPP)

• Normal expression requires signals from the
  central nervous system
• Neurons highly sensitive to hypoxemia
• Presence of biophysical variables implies the
  absence of clinically significant CNS hypoxia at
  the time of testing
• Biophysical variables may also be lost with fetal
  sleep cycles, transplacental passage of maternal
  sedatives and glucocorticoids

25
Biophysical Profile (BPP)

• Variables are lost in the reverse order of their
  development as hypoxia worsens
• Reactivity / breathing
• Movement
• Tone
• Testing may be initiated as early as 26 weeks
• More common at 32-34 weeks
• Approximately 80 of late stillbirths will
  demonstrate abnormal biophysical variables

26
Biophysical Profile (BPP)

• False negative tests (rare)
• NPV 99.9
• False positive tests (common)
• PPV 50

27
Biophysical Profile (BPP)
Fetal movements 3 or more discrete body or limb movements within 30 minutes of observation. An episode of active continuous movement is counted as one movement.
Fetal tone 1 or more episodes of extension of a fetal extremity or fetal spine with return to flexion
Fetal breathing movements 1 or more episodes of rhythmic breathing movements of 30 seconds within a 30 minute
Amniotic fluid volume Single pocket of fluid is present measuring 2 cm in 2 perpendicular planes
Non-stress test At least 2 episodes of FHR accelerations of at least 15 bpm and at least 15 seconds duration from onset to return associated with fetal movement within a 30 minute observation period
28
BPP and Perinatal Mortality
Score Interpretation Perinatal Mortality (per 1000 live births)
8-10 Normal 1.86
6 Equivocal 9.76
4 Abnormal 26.3
2 Abnormal 94.0
0 Abnormal 285.7
The perinatal mortality is 0.8/1000 for
structurally normal fetuses with a normal test
within 7 days.
29
BPP and Risk of Cerebral Palsy
30
Doppler Ultrasound

• Measures placental resistance to fetal perfusion

31
Dopplers in Pregnancy

• 1977 First use of Doppler ultrasonography to
  study flow velocity in the fetal umbilical artery
• Volume of flow in the UAs increases with
  advancing gestation
• Increased vascular impedance detected in the 1st
  trimester gradually decreases due to
• Growth of placental unit
• Increase in the number of the functioning
  vascular channels

32
Umbilical artery Dopplers
33
Umbilical artery Dopplers
34
Uses for Dopplers

• If Doppler is available, it may be used for the
  following reasons
• To identify a fetus with IUGR who registers later
  and you are uncertain of the gestational age
• Under further investigation to identify patients
  at risk for pre-eclampsia

35
Fetal movement assessment

• Approximately 10 of women complain of decreased
  fetal movement (DFM)
• Near-term fetuses spend approximately 25 of
  their time in a quiet sleep state and 60-70 in
  an active sleep state
• Longest period without fetal movements in a
  normal fetus is about 75 minutes
• Fetal movement appears to peak between 9pm and
  1am
• Hypoglycemia is associated with increased fetal
  movement
• 3rd trimester DFM is associated with a 10 fold
  increase in perinatal mortality
• Over 50 of the perinatal mortality in these
  patients is diagnosed at presentation

36
Fetal Movement

• DFM may be a compensatory mechanism with
  hypoxemia
• Fetal paralysis decreases p02 by 30
• Decreased pO2 causes bradycardia and transient
  hypertension
• Other causes of DFM include
• Decreased amniotic fluid
• Maternal drug sedation
• Uterine anomaly
• Placental position
• Maternal obesity
• Smoking

37
Evidence for Kick Counts

• Neldam et al (1983)
• Randomized trial conducted in Denmark
• Fetal movement counting was associated with a 73
  reduction in avoidable stillbirths
• RR 0.27, 95 CI 0.08-0.93
• Grant et al (1989)
• N 68,654
• Results no significant difference in potentially
  avoidable late fetal deaths between women who
  were instructed to count routinely and controls
• Mangesi et al (2007)
• Completed a systematic review which concluded
  insufficient evidence to recommend routine fetal
  movement counting to prevent stillbirth

38
Diagnosis of DFM

• No standard method of diagnosis
• Wide physiologic variation among fetuses
• Use as a primary means of fetal surveillance has
  not been verified in controlled prospective
  studies

39
Who should we test antenatally?
40
Indications for Testing

• Maternal

• Fetal

• Diabetes Mellitus
• Hypertension
• SLE
• Renal Disease
• AMA
• Thrombophilias

• Multiples
• Oligohydramnios
• Growth restriction
• Decreased fetal movement

41
Diabetes Mellitus

• 1993 Lagrew et al.
• Reviewed 13 studies using NST weekly for fetal
  surveillance
• Results Among the 23 stillbirths reported within
  a week of a reactive NST which did not result
  from acute clinical events 10 women had IDDM
• Conclusions Frequency of testing for women with
  diabetes increased to twice per week
• 1995 Kjos et al.
• Analyzed 2134 women with GDM who had twice weekly
  NST and weekly AFIs
• Results No stillbirths within 4 days of the last
  test
• Overall corrected stillbirth rate for the group
  was 1.4/1000

42
Hypertension of Pregnancy

• Includes chronic hypertension, pregnancy-induced
  hypertension and pre-eclampsia
• Pathophysiology
• Vasoconstriction affecting the uteroplacental
  circulation, intervillous space blood flow may be
  compromised and this can result in interruption
  in the supply of oxygen to the fetus
• Chronic fetal compromise resulting from
  uteroplacental insufficiency caused by these
  various hypertensive disorders may result in
  intrauterine growth restriction (IUGR) and
  abnormal fetal heart rate patterns

43
Hypertension of Pregnancy

• 1993 Sibai et al. recommended testing all
  chronic hypertensives
• 2007 Sibai and colleagues recommend testing only
  those hypertensive patients with pre-eclampsia
  and/or IUGR
• ACOG Practice Bulletin
• Does not recommend antepartum fetal testing in
  patients with mild to moderate blood pressure
  abnormalities on no medications and in the
  absence of preeclampsia and/or IUGR

44
Multiples

• NST is the primary method for fetal heart rate
  testing in twins
• Initial reports used independent electronic fetal
  monitoring systems for each fetus and reported
  failure rates of 2-15 in successfully capturing
  both fetuses
• Studies found that reactive NSTs conferred a good
  prognosis with no perinatal deaths and rates of
  growth restriction ranging from 8-28
• Nonreactive NSTs were associated with rates of
  fetal growth restriction of 55-100 and perinatal
  mortality rates of 50 or higher

45
Multiples

• Knuppel et al assessed the impact of initiating
  routine NSTs on all twins after 31 weeks
  gestation.
• Compared a historical group of 129 twin pairs not
  receiving routine NSTs to a subsequent group of
  90 twin pairs receiving routine weekly NSTs.
• 6/258 fetuses (2.3) in the control group had
  perinatal deaths, while there were no deaths in
  the routine NST group.

46
Growth Restriction

• Incidence Affects 15 of pregnancies
• Defined as lt10ile for gestational age in most
  studies
• Pathophysiology reduction of uterine perfusion
  decreases fetal glucose and amino acid delivery
  which leads to down-regulation of both the
  insulin and the insulin-like growth factor-1
  endocrine axis and hepatic glucose metabolism.
• Glycogenolysis with a decrease in liver size,
  redirection of gluconeogenic amino acids from
  endogenous protein breakdown, and eventually,
  delayed longitudinal growth

47
Growth Restriction

• 2000 McGowan et al.
• Pilot trial of 167 woman with U/S identified IUGR
  were randomized to 2x weekly testing versus every
  2 week testing
• Results No different in maternal morbidity if
  emergent C/S and unable to assess fetal primary
  outcome of combined morbidity
• Women in 2x weekly group had more testing, higher
  rates of IOL (25) and earlier deliveries (4
  days)
• 2004 Odibo et al. constructed a decision
  analysis model to determine best antenatal
  testing strategy for IUGR fetuses
• Compared with the other options, biophysical
  profile was the best strategy to guide physicians
  on the timing of the delivery of the preterm
  growth-restricted fetus
• Individual tests have a limited ability to
  distinguish between physiologic and pathologic
  variation in fetal status

48
Postdates

• Incidence 4-19 of pregnancies reach or exceed
  42 weeks gestation
• Divon et al. evaluated fetal and neonatal
  mortality rates in 181,524 accurately dated term
  and prolonged pregnancies
• Study showed a small but significant increase in
  fetal mortality in accurately dated pregnancies
  that extend beyond 41 weeks gestation and
  demonstrated that fetal growth restriction is
  independently associated with a large increase in
  perinatal mortality in these pregnancies

49
Postdates

• 2004 Caughey et al. showed several maternal and
  fetal complications evaluated in a large (n
  45,673) retrospective, cohort study
• Conclusion risks to both mother and infant
  increase as pregnancy progresses beyond 40 weeks'
  gestation, and that antenatal fetal testing
  should begin sooner than current recommendation
  of 42 weeks of gestation
• 2007 Cochrane Database of Systematic Review
• 26 trials of variable quality were included
• Routine induction of labor after 41 weeks
  gestation appears to reduce perinatal mortality
• Not enough evidence to evaluate the effects of
  antenatal testing on fetal wellbeing.

50
History of stillbirth

• Women who have suffered one stillbirth are at
  increased risk for perinatal mortality in
  subsequent pregnancies
• The National Institute of Neurological Diseases
  and Stroke determined that patients with previous
  stillbirths had a perinatal mortality rate of
  73/1000 in subsequent pregnancies and nearly 2
  of their surviving children were neurologically
  abnormal at 1 year of age
• UK study reported that the risk of poor outcomes
  in subsequent pregnancies was more than doubled
  among women with previous stillbirths

51
History of Stillbirth

• Freeman et al. reported on 337 women with
  histories of stillbirth who were followed with
  antenatal testing
• No increased risk of positive contraction stress
  test results even though the stillbirth only
  group probably had more tests per patient than
  the general antepartum surveillance population
• Antenatal testing has the potential to increase
  the risk of premature delivery.
• Mothers with medical or obstetrical problems and
  past stillbirths were more likely to have labor
  inductions and cesarean sections and their
  neonates were more likely to have respiratory
  distress syndrome.

52
History of Stillbirth

• 1991 Weeks et al. showed a cohort of 300 women
  whose sole indication for antepartum testing was
  a past history of stillbirth
• Included patients seen at two institutions in
  southern California between 1979-1991
• Results Otherwise healthy women with histories
  of a previous stillbirth were followed with
  antepartum fetal testing
• Stillbirth recurrence risk was low (1/300).
• National rate 7-9/1000
• Conclusions fetal testing can avert recurrent
  stillbirths

53
Management of Abnormal Testing
54
Abnormal Testing

• Must be tailored to the clinical scenario
• Maternal reports of decreased fetal movement
  should be evaluated by an NST, CST, BPP, or
  modified BPP
• If normal, no further testing required
• Nonreactive NST or an abnormal modified BPP
  generally should be followed by additional
  testing
• Positive CST with NST nonreactivity
• Consequence of hypoxia-induced acidosis and
  indicates that delivery is warranted
• Negative CST with NST nonreactivity
• Results from prematurity, maternal exposure to
  certain drugs or medications, fetal sleep cycle,
  or preexisting neurologic complications

55
Abnormal Testing

• Biophysical profiles less than 4 should result in
  expeditious delivery
• Oligohydramnios requires further evaluation

56
Does AntepartumTesting Work?
57
Perinatal Mortality Rate
58
Fetal Mortality Rate
59
Benefits and Costs of Antenatal Testing

• Economic analysis remains an important part of
  health care secondary to the fact that resources
  are limited and overall health care costs are
  rising quickly.
• Miller et al. identified 15,482 high-risk
  obstetric patients who underwent modified
  biophysical profile testing
• Results
• 54,617 exams were performed
• The cost of a modified biophysical profile was
  estimated by assessing the professional and
  technical fees at our own institution and then
  applying a costcharge ratio of 0.6.
• Total cost for this testing program was
  17,192,661.
• If one calculates that 158 stillbirths were
  potentially prevented by antepartum testing, the
  cost per stillbirth averted is 108,814.

60
Guidelines for Outpatient Antenatal Surveillance
Primary Condition Gestational Age to initiate testing Testing Modality Frequency
Antiphospholipid antibody syndrome (One or more episodes of venous, arterial, or small vessel thrombosis and/or morbidity with pregnancy) 26-28 wk NST Biweekly with weekly AFI
Postdates pregnancy 41 wk NST/AFI Weekly
Cholestasis of Pregnancy At diagnosis NST Weekly
Decreased Fetal Movement At diagnosis NST If reactive with no decels, no repeat
Gestational Diabetes (A1) well controlled with normal growth Not indicated Not indicated Not indicated
Diabetes Mellitus including A2, B, C and D without HTN or renal disease 32-34 wk NST Biweekly
Diabetes Mellitus including any class with HTN, renal disease, and R-F 28-32 wk NST AFI Biweekly (AFI weekly)
Elevated AFP (gt3.0 MoM)/HCG 30-32 wk U/S for growth Only if FGR
Major Fetal Anomaly (Gastroschisis and others at discretion of MD) 34 wk NST Weekly
Growth Restriction (rec. MFM consult for specific plan) At diagnosis (or 26 wks) NST/AFI Biweekly, Weekly
61
Guidelines (cont)
Primary Condition Gestational Age to initiate testing Testing Modality Frequency
Chronic HTN well controlled with normal growth 32-34 wk NST Weekly
Chronic hypertension poorly controlled (on gt1 medication) 28-32 wk NST Biweekly, weekly AFI
Chronic HTN well controlled with normal growth At diagnosis NST Biweekly, weekly AFI
Hyperthyroidism (on meds) 34-36 wk NST Weekly
Hemoglobinopathies (hemoglobin SS, Sc or S-thalassemia) 32-34 wk NST Biweekly
Maternal Age at Delivery (35) 36 wk NST Weekly
Multiples Di/Di Twins - Normal Growth - Growth Restriction 34 wk At diagnosis NST NST/AFI Weekly Biweekly, MFM consult
Multiples Mono/Di Twins - Normal growth - Growth Restriction 32 wk At diagnosis NST NST/AFI Weekly Biweekly, MFM consult
Oligohydramnios (AFI lt5cm) 28 weeks or at diagnosis NST, AFI Biweekly, weekly AFI
Previous IUFD 34 wk or 1 wk prior to previous IUFD NST Weekly
Renal Disease/Transplant 32 wk NST Weekly
SLE without comorbidy 32 wk NST Weekly
62
References

• 1. American College of Obstetricians and
  Gynecologists. Antepartum Fetal Surveillance.
  ACOG Practice Bulletin 9, American College of
  Obstetricians and Gynecologists, Washington DC
  1999.
•  2. Signore, Caroline MD MPH et al. Antenatal
  Testing A Re-evaluation. Semin Perinatol
  200832(4) 231-322.
•  3. Signore C, Freeman RK, Spong CY. Antenatal
  testing a re-evaluation executive summary of a
  Eunice Kennedy Shriver National Institute of
  Child Health and Human Development Workshop.
  Obste Gynecol. 2009 Mar 113(3)687-701.
•  4. Neilson JP, Alfirevic Z. Doppler ultrasound
  for fetal assessment in high risk pregnancies.
  The Cochrane Database of Systematic Reviews 2000,
  Issue 2. Art. No. CD000073
•  5. Pregnancy outcomes in the Diabetes Control
  and Complications Trial. Am J Obstet Gynecol
  1996174134353
•  6. Lagrew DC, Pircon RA, Towers CV, Dorchester
  W, Freeman RK. Antepartum fetal surveillance in
  patients with diabetes when to start? Am J
  Obstet Gynecol 199316818205.

63
References

•  7. Devoe LD, Ware DJ. Antenatal assessment of
  twin gestation. Semin Perinatol 19951941323.
•  8. Management of Postterm Pregnancy. ACOG
  Practice Bulletin No. 55. American College of
  Obstetricians and Gynecologists. Obstet Gynecol
  200410463946.
•  9. Reddy UM. Prediction and prevention of
  recurrent stillbirth. Obstet Gynecol
  2007110115164.
•  10. Spong CY. Antenatal fetal monitoring. In
  Queenan JT, editor. Management of high-risk
  pregnancy. 4th ed. Malden (MA) Blackwell
  Science 1999.
• 11. Kendall-Hunt, (2003). Fetal Heart Monitoring
  Principles and Practices. (3rd edition)  Dubuque,
  IA
• 12. Association of Womens Health, Obstetrical
  and Neonatal Nursing
• 13. National Institute of Child Health and Human
  Development (NICHHD) Research Planning Workshop
  (1999).  Electronic fetal heart rate monitoring
  Research guidelines for interpretation.  Journal
  of Obstetric, Gynecologic and Neonatal Nursing,
  26. 635-640.
•  14. Reece EA, Coustan DR and Gabbe SG (2004).
   Diabetes in Women Adolescence, Pregnancy and
  Menopause.  3rd Ed.  Lippincott, Williams and
  Wilkins

64
Questions?