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Antenatal Testing

by Veronica Gillispie, MD, FACOG
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    00:01 Now we will discuss antenatal testing.

    00:06 So the purpose of antenatal testing is to ensure fetal well being.

    00:10 And when we say reassure us or ensure fetal well being, we mean that there are no signs of fetal asphyxia.

    00:18 So let's first talk about the non-stress test.

    00:22 So the non-stress test is performed by doing the external fetal monitoring to look at the fetal heart rate.

    00:29 We then determined if the fetal heart rate is reactive which means fetal well being is reassured or is it non-reactive.

    00:37 Meaning there is additional testing needed to be done to assure fetal well being.

    00:42 Reactive and this is very important, means that there is two accelerations of greater than 15 beats per minute lasting at least 15 seconds over a 20 minute time period.

    00:54 So again you are looking at a 20 minute time period on the external fetal monitor and you're looking to find two accelerations of greater than 15 beats per minute each lasting for at least 15 seconds.

    01:05 So the next type of antenatal testing is the biophysical profile.

    01:10 Now with the biophysical profile, you're looking at 5 different categories expecting to see certain things in this category.

    01:20 Patients are given a two if the fetus performs the maneuvers that we're looking for and 0 if they do not perform the maneuvers.

    01:28 Again give 30 minutes to observe it.

    01:30 So we're looking at fetal movement, we're looking at fetal tone, fetal breathing, the amniotic fluid and again the non-stress test.

    01:40 So with the fetal movement we're looking to see three growth movements within that 30 minute time period.

    01:46 Fetal tone is looking for 5 movements, like the hands moving, the fingers, opening and closing the palm.

    01:53 Fetal breathing we're looking for sustained breathing for 30 seconds over that 30 minute time period.

    01:59 Amniotic fluid volume, we're really just looking at the maximum vertical pocket and we want that to be at least 2 centimeters and then we've already discussed the non-stress test.

    02:08 So if we had a score of 8 that is reassuring.

    02:13 That means that the fetus is doing well and there is no signs of fetal asphyxia.

    02:17 If there is a score of 6, this is considered equivocal.

    02:21 So it doesn't mean that we are reassured.

    02:23 But it also doesn't mean that the baby is concerning for asphyxia.

    02:28 However, if the patient is term, meaning 37 weeks that means we need to deliver that fetus.

    02:33 At a score of 4, it is a little bit concerned as far as asphyxia and we do need to deliver at that point.

    02:40 So the bio-physical profile can be used when the non-stress test is not reactive as a confirmation that the baby is doing okay.

    02:50 However, you can do a modified bio-physical profile when you're just looking that the fetus.

    02:56 And you take out the non-stress test as one of those components.

    02:59 So then you're score is out of 8 instead of out of 10.

    03:05 So the next antenatal testing that we use is a contraction stress test.

    03:09 So with a contraction stress test we induce contractions and that can either be through nipple stimulation or can be induced by given pitocin.

    03:19 And we're looking to see that a patient has contractions over a 10 minute time frame.

    03:25 Now this test we do not want to be positive.

    03:29 So it's a little different than a non-stress test.

    03:31 If the test is positive, that means that more than 50% of the contractions are associated with a late deceleration.

    03:39 The test is equivocal when there is intermittently decelerations but less than 50%.

    03:46 And the test is negative when there is less than 50% of the contractions associated with late decelerations.

    03:52 Again for the contraction stress test we want a negative result to reassure that the fetus can tolerate labor.

    04:00 Pay attention to this slide because this is high yield.

    04:05 And then the final test is the umbilical artery Doppler.

    04:07 Now this is a test that is performed by doing an ultrasound looking at the Doppler of the umbilical artery.

    04:15 And we do this when we are suspecting fetal growth restriction.

    04:19 Now our results can show a normal SD, systolic diastolic ratio.

    04:24 Or it can show absent or even worse it can show reversal flow.

    04:29 If it is -- if the flow is absent or reversal then that indicates that there is an increased resistance in the placenta.

    04:36 So let's look at a question.

    04:39 A 27 year old gravida 1 para 0 female at 28 weeks and 3 days of gestation with a history of chronic hypertension presents for an antenatal visit.

    04:50 She has had no issues this pregnancy.

    04:52 All antenatal testing has been within normal limits.

    04:55 She takes labetol for her chronic hypertension.

    04:58 On physical exam, blood pressure is 140 over 95.

    05:02 Her heart rate --excuse me the fetal heart rate, is a 150 beats per minute.

    05:07 And the fundal height for the mom is 23 centimeters.

    05:10 Now when we think about that 23 centimeters, at 28 weeks gestation, that sounds a little small to me.

    05:18 So the next best step in her management is A.

    05:22 A fetal ultrasound B. Fetal Doppler of the umbilical artery.

    05:26 C. Contract stress test or D. Biophysical profile.

    05:32 So in this case, we first want to do fetal ultrasound.

    05:35 Now there's lot of reasons, like the fundal height maybe small.

    05:38 It could be because there is decreased amniotic fluid.

    05:41 It could be because the baby is small or it could be our measurements are not that great.

    05:45 So we want to confirm that the measurement is small, first by fetal ultrasound.

    05:49 If the fetus is indeed small, then the fetus will warrant, a fetal Doppler of the umbilical artery.

    05:54 But the next best step in her management, is to perform the fetal ultrasound.


    About the Lecture

    The lecture Antenatal Testing by Veronica Gillispie, MD, FACOG is from the course Antenatal Care. It contains the following chapters:

    • Antenatal Testing
    • Non-Stress Test
    • Biophysical Profile
    • Contraction Stress Test

    Included Quiz Questions

    1. 2 accelerations of over 15 beats per minute from the baseline fetal heart rate, each lasting over 15 seconds, are seen on a 20 minute strip.
    2. 2 accelerations of 10 beats per minute from the baseline fetal heart rate, each lasting 15 seconds, are seen on a 20 minute strip.
    3. 2 accelerations of 15 beats per minute from the baseline fetal heart rate, each lasting over 15 seconds, are seen on a 30 minute strip.
    4. 1 acceleration of 15 beats per minute from the baseline fetal heart rate lasting 15 seconds is seen on a 10 minute strip.
    5. 1 acceleration of 20 beats per minute from the baseline fetal heart rate, lasting 30 seconds, is seen on a 20 minute strip.
    1. Umbilical artery doppler
    2. Fetal tone
    3. Fetal breathing
    4. Amniotic fluid volume
    5. External fetal heart rate monitoring
    1. 4/8, plan to deliver immediately
    2. 6/8, further testing recommended
    3. 6/10, plan to deliver
    4. 4/10, further testing required
    5. 8/10, fetal reassurance.
    1. If more than 50% of induced contractions are associated with late decelerations in the fetal heart rate over 10 minutes.
    2. If less than 50% of induced contractions of associated with late decelerations in the fetal heart rate over 10 minutes.
    3. If no accelerations are noted over a period of 20 minutes of monitoring.
    4. If greater than 2 accelerations are noted over a period of 20 minutes of monitoring.
    5. If there are no decelerations observed over 20 minutes.
    1. That there are no signs of fetal asphyxia
    2. That there are is normal fetal movement
    3. That there are no signs of fetal growth restriction
    4. That there is enough amniotic fluid
    5. That there is normal umbilical artery flow
    1. Perform an umbilical artery doppler to evaluate for increased resistance in the placenta
    2. Perform a non-stress test
    3. Perform a contraction stress test
    4. Perform a biophysical profile
    5. Advise the patient to quit smoking immediately

    Author of lecture Antenatal Testing

     Veronica Gillispie, MD, FACOG

    Veronica Gillispie, MD, FACOG


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