9.2d Antepartum Assessment using Electronic Fetal Monitoring

Question 1

Antepartum Assessments

Answer 1

• 1st and 2nd trimester goal is to diagnose fetal anomalies

- 3rd trimester goal is to determine if intrauterine environment can still support the fetus

Question 2

Primary Tests

Answer 2

• NST (Non Stress Test)

- mBPP (Modified Biophysical Profile)

Question 3

Follow Up Evaluations

Answer 3

• Complete BPP
• CST (Contraction Stress Test)
• Used if patient has consistent abnormal mBPP or non-reactive NST
• Done at 32-34 weeks and earlier for women with risk factors
• Preformed 1-2 times weekly

Question 4

Non-Stress Test

Answer 4

• The basis is that fetus has characteristic heart rate patterns in response to fetal movement, uterine contractions or stimulation.
• Accelerations in heart rate is mostly associated with movement
• Absence of accelerations means the fetus is asleep but can also be caused by CNS depression medications, chronic smoking, fetal malformations

Question 5

NST

Answer 5

• Easy to preform and has no contraindications

Disadvantages

• Requires testing twice a week
• High false-positive and negative rate
• Less reliable than BPP and CST

Question 6

NST Procedure

Answer 6

• FHR and Contractions are recorded with doppler and tocodynamometer
• Fetal activity is detected via concurrent accelerations in FHR
• If fetal movement cannot be detected, a women will be asked to push a button when she feels fetal movement
• Movement does not need to be recorded for the test to be considered reactive
• Test usually takes 20-30 minutes or longer if fetus is in sleep state (drinking orange juice can help stimulate fetus in sleep states to increase blood sugar levels)

Question 7

Vibroacoustic Stimulation (VAS)

Answer 7

• Helps to change fetus from sleep to wake state if initial test is non-reactive
• At 26 weeks gestation it shortens the amount of time required to complete the test

Question 8

Interpretation of NST

Answer 8

• Can be either reactive or non-reactive
• Reactive is normal
• Non-reactive requires further evaluation (extended by 20 minutes)
• Non-reactive longer than 40 minutes requires CST or BPP
• Test is done 1-2 times a week

Question 9

Vibroacoustic Stimulation (FAST)

Answer 9

• Preformed in conjunction with NST
• Monitor fetus for 5 minutes before stimulation to establish baseline FHR
• If FHR is non-reactive, sound is used for 3 seconds on the maternal abdomen over fetus head
• Accelerations in FHR should be seen within 3 minutes
• If still non-reactive repeat for 3 times in 1 minute intervals
• Safe for babies

Question 10

Hypoglycemia from Diabetes

Answer 10

• Risk is higher in pregnancy because symptoms may go unnoticed
• Risk is highest in 1st trimester
• Pregnancy can also increase risk of DKA. You can test it with ketones in urine

Question 11

NST Reactive Vs Non-Reactive

Answer 11

Reactive - 2 accelerations in 20 minutes lasting 15+ seconds at least 15 bpm above baseline.
(Before 32 weeks, acceleration can be 10+ seconds at least 10 bpm above baseline)

Non-reactive - Does not have 2 accelerations in 20 minutes

Question 12

Contraction Stress Test (CST)

Answer 12

• Also called oxytocin challenge test (OCT)
• Identify jeopardized fetuses that are stable at rest but show compromise with stress
• Uterine contractions decrease placental blood flow and perfusion. This can cause hypoxia and decelerations
• Produces fewer false positives than NST
• Cannot predict acute fetal compromise such as placental abruption, umbilical cord accidents
• Invasive procedure that requires oxytocin stimulation
• Cannot be preformed on women who cannot give vaginal birth at the time the test is done

Question 13

CST CONTRAINDICATIONS

Answer 13

• Preterm labor
• Placental previa
• Vasa previa
• Cervical Insufficiency
• Multiple gestations
• Previous c-section birth

Question 14

CST Procedure

Answer 14

• Monitored with fetal ultrasound transducer and uterine tocodynamometer
• Observed 10-29 minutes to establish baseline and variability

Question 15

Nipple-Stimulated Contraction Test

Answer 15

• Massage nipples to release oxytocin
• One way to stimulate nipple is applying warm washcloth to both breasts for a few minutes and then massaging nipples for 10 minutes
• Another way is to massage nipples through clothes for 2 minutes, rest for 5 minutes, then repeat until uterine contractions occur.
• Hyperstimulation (uterine contractions lasting more than 90 seconds or 5 or more contractions in 10 minutes) - once this occurs stimulation should stop

Question 16

Oxytocin Stimulated Contraction Test

Answer 16

• IV oxytocin is given until 3 uterine contractions of moderate intensity lasting 40-60 seconds occurs over a 10 minute period

Question 17

CST Results

Answer 17

Negative - No late decelerations
Positive - Repetitive late decelerations

Positive CST Test Results are Associated With

• Intrauterine fetal death
• Late FHR decelerations in labor
• IUGR
• Meconium stained amniotic fluid

Question 18

CST Results IN DETAIL

Answer 18

Negative - 3 uterine contractions in 10 minute period with no late or significant variable decelerations

Positive - Late decelerations occur in 50%+ contractions even if there is fewer than 3 contractions in 10 minutes. Hospitalization

Suspicious (Equivocal) - Prolonged/Variable/Late Decelerations occurring in less than 50% of contractions. Further evaluation and test is repeated next day.

Equivocal Hyperstimulatory - Decelerations that occur with contractions more than every 2 min or last longer than 90 seconds. Repeat test the next day

Unsatisfactory - Failure to produce 3 uterine contractions within 10 minutes