Fetal Biophysical Profile

Joyce Mwatonoka, MD5The University of Dodoma

April 2017

Introduction Parameters of biophysical profile Scoring and interpretation Other tests References

Contents

It is a technique employed to forecast fetal well-being focus on fetal biophysical findings that include heart rate, movement, breathing, and amniotic fluid production

It contains 5 parameters; nonstress test (NST), fetal breathing, fetal movements, muscle tone and amniotic fluid volume

Introduction

Modified Biophysical Profile consists of NST and ultrasonographically determined amniotic fluid index (AFI)

Modified BPP is considered abnormal (non reassuring) when the NST is non-reactive and/or the AFI is < 5

Cont…

Currently, nonstress test is the most widely used primary testing method for assessment of fetal well-being

It describes FHR acceleration in response to fetal movement as a sign of fetal health

Involved the use of Doppler-detected FHR acceleration coincident with fetal movements perceived by the mother

1. Nonstress test

As hypoxia develops, these fetal heart rate accelerations diminish

Normal results; two or more accelerations that peak at 15 bpm or more above baseline, each lasting 15 seconds or more, and all occurring within 20 minutes of beginning the test

Cont…

A 40-minute or longer tracing to account for fetal sleep cycles should be performed before concluding that there was insufficient fetal reactivity

Studies show 1 acceleration was just as reliable as 2 in predicting healthy fetal status

Also accelerations with or without fetal movements may be accepted

Cont…

Abnormal results;1) baseline oscillation of less than 5 bpm, 2) absent accelerations, and 3) late decelerations with spontaneous uterine

contractions

Cont…

Abnormal results were associated consistently with evidence of uteroplacental pathology eg;

IUGR placental infarction Oligohydramnios fetal acidemia and meconium

Cont…

Interval between testing set at 7 days; but more frequent testing is advocated for women with post-term pregnancy, multifetal gestation, type 1 diabetes mellitus, IUGR, or gestational hypertension

In these circumstances, twice-weekly tests, with additional testing is advised

Cont…

Passive unstimulated fetal activity commences as early as 7 weeks’ gestation and becomes more sophisticated and coordinated by the end of pregnancy

Between 20 and 30 weeks, general body movements become organized, and by 36 weeks behavioral states are established in most normal fetuses

2. Fetal movements

Four fetal behavioral states described: State 1F is a quiescent state; quiet sleep, with

a narrow oscillatory bandwidth of the FHR State 2F includes frequent gross body

movements, continuous eye movements, and wider oscillation of the FHR. It is analogous to REM or active sleep in the neonate

Cont…

State 3F includes continuous eye movements in the absence of body movements and no heart rate accelerations

State 4F is one of vigorous body movement with continuous eye movements and heart rate accelerations. This state corresponds to the awake state in newborns

Cont…

Fetuses spend most of their time in states 1F and 2F (>75% at 38 weeks)

Mean length of the quiet or inactive state for term fetuses was 23 minutes (up to 75min)

Cont…

Amnionic fluid volume is another important determinant of fetal activity

Perception of 10 fetal movements in up to 2 hours is considered normal

Cont…

Two types of respiratory movements; The first are gasps or sighs, which occurred at

a frequency of 1 to 4 per minute The second, irregular bursts of breathing,

occurred at rates up to 240 cycles per minute These latter rapid respiratory movements

were associated with REM sleep

3. Fetal breathing

Diurnal variation, because breathing substantively diminishes during the night

But, increases somewhat following maternal meals

Total absence of breathing was observed in some normal fetuses for up to 122 minutes, indicating fetal evaluation to diagnose absent respiratory motion may require long periods of observation

Cont…

Decreased uteroplacental perfusion may lead to diminished fetal renal blood flow, decreased urine production, and ultimately, oligohydramnios

Amniotic fluid index < 5 cm or a maximum deepest vertical pocket < 2 cm are acceptable criteria for diagnosis of oligohydramnios

4. Amniotic fluid volume

Normal; ≥ 1 pocket measuring 2 cm in two perpendicular planes (2 × 2 cm pocket)

Cont…

Normal; ≥ 1 episode of extension (limb or trunk) with return of flexion

5. Fetal muscle tone

Biophysical profile score

8-10; no fetal asphyxia, repeat weekly 6; suspected chronic asphyxia, if >36 weeks

deliver, if less repeat test in 4-6hours 4 and below; strongly suspect asphyxia, if

>36weeks deliver, if not repeat after 4-6 hours for 120minutes, persistent score <5 deliver regardless of GA

Interpretation of the score

Other tests…

Formerly known as oxytocin challenge test Intravenous diluted oxytocin was used to

stimulate contractions, and the FHR response was recorded

The criterion for a positive test result, that is, an abnormal result, was uniform repetitive late fetal heart rate decelerations (which could be the result of uteroplacental insufficiency)

Contraction stress test

Nipple stimulation to induce uterine contractions is usually successful for contraction stress testing

2-minute nipple stimulation ideally will induce a pattern of 3 contractions per 10 minutes, if not after 5 minutes, retry, if unsuccessful, diluted oxytocin

Cont…

Loud external sounds have been used to startle the fetus and thereby provoke heart rate acceleration

An acoustic stimulator is positioned on the maternal abdomen, and a stimulus of 1 to 2 seconds is applied

A positive response is defined as the rapid appearance of a qualifying acceleration following stimulation

Acoustic stimulation tests

Arterial Doppler waveforms are helpful to assess the downstream vascular resistance

Three fetal vascular circuits; umbilical artery, middle cerebral artery, and ductus venosus can be assessed to determine fetal health

Maternal uterine artery Doppler velocimetry has also been evaluated to predict placental dysfunction

Doppler Blood Flow Velocity/Doppler velocimetry

Venous Doppler parameter provide information about cardiac forward function (cardiac compliance, contractility and after load)

Fetuses with abnormal cardiac function show pulsatile flow in the umbilical vein (UV)

Normal UV flow is monophasic

Cont…

Williams Obstetrics 24e 2014 DC Dutta’s Text Book of Obstetrics 7E REVISED

2014

References

Thank you!