Antepartum Fetal Surveillance Flashcards
What techniques do we use for Antepartum Fetal Surveillanc?
- maternal perception of fetal movement
- contraction stress test (CST)
- nonstress test (NST), biophysical profile (BPP)
- modified BPP
- umbilical artery Doppler velocimetry
How to do fetal movement assessment?
- Lie on side and count distinct fetal movements
- 10 or more in up to 2 hours= reassuring
- Can stop counting once 10 movements perceived
- Mean time to 10 movements was 20.9 min - Count fetal movements for 1 hr 3x/week
- Reassuring if equal or exceeding previous baseline count
How to do NST? how to properly do Vibroacoustic stimulation? What’s the physiology behind NST? What’s reactive? What’s non reactive? What if you see decels (what kind of decels are ok)?
- At least 20min, but it may be necessary to monitor the tracing for 40 minutes or longer to take into account the variations of the fetal sleep–wake cycle
- A vibroacoustic stimulus is applied for 1–2 seconds. If vibroacoustic stimulation fails to elicit a response, it may be repeated up to 3 times for progressively longer durations of up to 3 seconds.
- Based on premise that FHR will temporarily accelerate w/ movement when fetus is not acidotic or neurologically depressed. Loss of reactivity can occur w/ any CNS depression
- Reactive: ≥ 2 (15x15) accels w/I 20 min
- For <32 weeks, 10x10 counts as accel
- Non-reactive: lack of sufficient accels over 40 min period
Vibroacoustic stim may be used up to 3 times for up to 3 seconds - Variable decels are seen in 50% of NSTs.
- -Nonrepetitive and <30 sec are not associated w/ fetal compromise
- -Repetitive variables, at least 3 in 20 min are associated w/ increased risk of CS
- -Decels that persist for ≥ 1 min are associated with increased risk of CS for nonreassuring FHT and fetal demise
- What’s the physiology behind CST?
- What defines an adequate CST?
- How do you stimulate for adequate contractions?
- What’s a negative CST?
- What’s a positive CST?
- What’s Equivocal–suspicious CST?
- What’s Equivocal CST?
- What’s unsatisfactory CST?
- uterine contractions –> transiently worsen fetal oxygenation. If the fetus is suboptimally oxygenated, the intermittent worsening in oxygenation from contractions will lead to the FHR pattern of late decelerations
- An adequate uterine contraction pattern is present when at least 3 contractions persist for at least 40 seconds each in a 10-minute period
- Nothing if spontaneous uterine contractions of adequate frequency.
- Nipple stimulation
- IV pitocin
Negative: no late or significant variable decelerations
Positive: late decelerations after 50% or more of contractions (even if the contraction frequency is fewer than three in 10 minutes)
Equivocal–suspicious: intermittent late decelerations or significant variable decelerations
Equivocal: FHR decelerations that occur in the presence of contractions more frequent than every 2 minutes or lasting longer than 90 seconds
Unsatisfactory: fewer than three contractions in 10 minutes or an uninterpretable tracing
- Name all 5 components of the BPP and state exactly what each entails.
Nonstress test––may be omitted without compromising test validity if the results of all four ultrasound components of the BPP are normal 35
Fetal breathing movements––one or more episodes of rhythmic fetal breathing movements of 30 seconds or more within 30 minutes
Fetal movement––three or more discrete body or limb movements within 30 minutes
Fetal tone––one or more episodes of extension of a fetal extremity with return to flexion, or opening or closing of a hand
Determination of the amniotic fluid volume––a single deepest vertical pocket greater than 2 cm is considered evidence of adequate amniotic fluid (MVP 2-8; AFI 5-24)
Which componenet of the BPP is the last to disappear in fetal distress?
Fetal HR reactivity > breathing movement > gross fetal movement > tone > amniotic fluid
What’s a normal BPP score?
8/10 unless it’s oligohydramnios and 10/10
What to do 6/10 BPP?
If ≥ 37w0d, consider delivery
If < 37w0d, repeat BPP in 24 hrs
If repeat test ≤ 6, deliver
If repeat test > 6, observe and repeat per protocol
What to do with 4/10 BPP?
Typically deliver
If same day repeat test is ≤ 6, deliver
if <32w0d, additional monitoring may be appropriate
What to do with 0-2/10 BPP?
Deliver
If delivery is not planned antenatal testing should not be performed because results will not inform management
What’s the components of modified BPP?
NST + MVP
- What fetus can you use Umbilical Artery Doppler Velocimetry for?
- What are you measuring with Umbilical Artery Doppler Velocimetry?
- what’s abnormal result?
- What’s abnormal flow correlated with?
- IUGR
- S/D ratio compares the maximal or peak systolic flow with end-diastolic flow to evaluate downstream impedance to flow
- Abnormal: S/D ratio >95% for GA, reversal or absent end-diastolic flow
- Abnormal flow is correlated w/ small artery obliteration in placental tertiary villi and w/ fetal hypoxemia and acidemia, morbidity and mortality
What’s the negative predictive value for NST, CST, BPP, modified BPP, umbilical artery Doppler velocimetry?
- 99.8% for the NST
> 99.9% for the CST, BPP, and modified BPP.
100% for umbilical artery Doppler velocimetry
Low false-negative rate of antepartum fetal surveillance, defined as the incidence of stillbirth occurring within 1 week of a normal test result.
List Indications for Antepartum Fetal Surveillance Testing
Maternal conditions
- Pregestational diabetes mellitus
- Hypertension
- Systemic lupus erythematosus
- Chronic renal disease
- Antiphospholipid syndrome
- Hyperthyroidism (poorly controlled)
- Hemoglobinopathies (sickle cell, sickle cell–hemoglobin C, or sickle cell-thalassemia disease)
- Cyanotic heart disease
Pregnancy-related conditions
- Gestational hypertension
- Preeclampsia
- Decreased fetal movement
- Gestational diabetes mellitus (poorly controlled or medically treated)
- Oligohydramnios
- Fetal growth restriction
- Late term or postterm pregnancy
- Isoimmunization
- Previous fetal demise (unexplained or recurrent risk)
- Monochorionic multiple gestation (with significant growth discrepancy)
When to start antepartum fetal surveillance?
32 0/7 weeks of gestation.
However, in pregnancies with multiple or particularly worrisome high-risk conditions (eg, chronic hypertension with suspected fetal growth restriction), testing might begin at a gestational age when delivery would be considered for perinatal benefit
