Biophysical Profile & Color Doppler Ultrasound in the High Risk Pregnancy

Biophysical Profile and Color Doppler Ultrasound in the High Risk Pregnancy
Presented by: Dr. Farzad Afzali
Kasra Ultrasound Clinic

  • BPP is applying to detect prenatal asphyxia
• Doppler ultrasound is a modality for detecting fetal hypoxia and acidosis
• Doppler can also predict later pre- eclampsia at the 24-26 gestational weeks.

  • Hypoxia: Low oxygen tension
• Asphyxia: Low oxygen and high CO2
• Ischemia: Drop in blood flow

Comment
So, Doppler ultrasound can predict fetal distress sooner than BPP

  • Prediction of the effect of an asphyxial insult on the fetus requires a measure of:

Severity of the asphyxia
Duration of the asphyxia

  • 18-48 hours (Neuronal necrosis) 48-72 hours of white matter macroph. & Astrocy.)
> 4 days cavitation visible on head U/S

Comment
Fetal asphyxia may or may not be concomitant with clinical presentation (based on severity, duration & location of insult)

Comment
As you know, oligohydramnios may be:
Mild             AFI= 5-8cm
Moderate   AFI= 2-5cm
Severe       AFI<2cm
Only severe oligohydramnios is considered as an abnormal score.

  • Fetal movement and fetal tone develop between 7.5 and 9 weeks’ menstrual age
• Fetal breathing movements are detectable by, at least 17-18 weeks’ gestation
• The non-stress test is most reliable between 32 weeks and term (Ware, 1994).

Comment
So, BPP has a limited role for assessing fetal well being before 32 gestational weeks.

  • The non-stress test and fetal breathing movements are suppressed when the pH falls below 7.2.
• If the fetal pH falls below 7.10, fetal tone and fetal movements are abolished (Vintzileos, 1987).

  The biophysical profile score is continued for a maximum of 30 minutes Oligohydramnios is now defined as a pocket of amniotic fluid < 2.0 x 2.0 cm (Manning, 1995)

Perinatal Mortality and the Biophysical Profile Score

Comment
I think, if you are working in a center that peri natal mortality is 50/1000 for preterm delivered fetus (otherwise normal), if you visit a fetus with BPP= 4, you can wait until 35-37 gestational weeks cautiously. (perinatal mortality for BPP = 4 is 26/1000)

Color Doppler Ultrasound in the High Risk PregnancyDoppler ultrasound has three view of applying in the OB& GYN field.

1 – direct view for example in ovarian torsion or detecting vascularity of a fibroma.
2 – easy conceptional view for example to differentiating a benign ovarian mass from malignant one.
3- deep conceptional view for example in detecting fetal hypoxia and acidosis in pregnancy.

Uterine Artery 

  An early stage in fetal adaptation to hypoxemia

- central redistribution of blood flow ( brain-sparing reflex)
- increased blood flow to protect the brain, heart, and adrenals
- reduced flow to the peripheral and placental circulations

Doppler Wave Form of Early Stage of Fetal Hypoxemia

- increased end-diastolic flow in the middle cerebral artery (lower MCA pulsatility index or resistance index)
- decreased end-diastolic flow in the umbilical artery (higher umbilical artery RI or systole-to-diastole [S/D] ratio)

  Long term outcomes need to be examined:

Middle cerebral artery
Aorta
Umbilical artery
Uterine artery
IVC
Ductus venosus

Comment
• The first Doppler change is rising peak velocity in ductus venosum.
• It can not be measured by Doppler precisely because it is an angle related index.

The middle cerebral artery (MCA) in the fetal brain:

- normally high impedance
- most accessible to U/S imaging
- more than 80% of cerebral blood

MCA 

Comment
Average of both MCAs must be calculated for more precise result.

Fetal Aorta

Comment

• PI of thoracic aorta is sum of all branches PI below it, specially both umbilical and femoral arteries.
• It means that increased impedance against umbilical artery causes increasing PI of thoracic aorta.
• Placental insufficiency inhibits acid extraction from fetal body and causes acidosis.
continued

Comment
Acidosis causes peripheral arterial spasm & rises PI of femoral arteries, consequently increases thoracic aorta PI.
If fetal acidosis has an intrinsic cause, it will be expected that femoral artery PI will be effected more than umbilical PI.

The damage that obliterate small muscular arteries in placental tertiary stem villi

- flow or even reversed flow
-commonly associated with severe IUGR and oligohydramnios

Umbilical Artery 

Uterine Artery 

  • The best predictor of PIH is notch in the uterine artery and RI >58 % after 24 weeks of gestation.
• A/C ratio > 2.5 is considered pathologic.

Comment
I think that RI of uterine artery more than 75% (2 standard deviation above mean) must be considered as a limit for prediction of preeclampsia.

Uterine Artery

Pathological Changes in Venous Flows with FGR

Venous indices reflect:

• Ventricular function
• Fetal hypoxia
• Myocardial lactic acidosis

Decrease cardiac output secondary to myocardial dysfunction:

• Rise in CVP
• Increase in reverse flow in atrial systole
• Transmitted down venous system - the further from the heart the greater degree of cardiac dysfunction.

Pattern continued

DV ‘a’ wave decrease
Reverse EDF UA - Reverse ‘a’ wave
DV Pulsatile UV
Constriction of cerebral circulation
Death within 96 hours

Ductus Venosus - Normal

• Normal progression through pregnancy is for a decrease in proportion of blood flow from umbilical vein - 40 to 15% of total volume 2nd to 3rd trimester
• Leads to more flow to liver
• Increase in blood flow velocity with gestational age

Comment
We can find ductus venosum by rising color scale to 50 cm/sec at level of umbilical artery. It causes other vessels, except aorta ductus venosum, to disappear.

Ductus Venosum

Umbilical Vein
Umbilical vein displays pulsatility in first trimester but this disappears with advancing gestation in the pregnancy unaffected by FGR.

  The data on MCA PI on 5 year follow up is very worrying as the brain sparing effect commonly occurs before venous Doppler disturbances.

  In clinical practice, it is necessary to carry out serial Doppler investigations to estimate the duration of fetal blood flow redistribution.

The onset of abnormal venous Doppler results indicates deterioration in the fetal condition and iatrogenic delivery should be considered.

Comment

• It seems that arterial changes can lead directly to non-reactive NST, asphyxia and death because of brain damage.
• Venous changes are signs of fetal heart failure, so fetal death is due to heart damage.
• Therefore, fetal hypoxia and acidosis can end to fetal death, either by cardiac or brain failure.

Conclusion

The best predictor for fetal acidemia is PI of thoracic aorta.
The best predictor of fetal hypoxia is PI of MCA.

  • PI of MCA/PI of TA must be more than 0.9 before 30, less than 0.8 before the 34 and less than 0.75 before the 36 weeks of pregnancy.
• PI of MCA/ PI of UA must be >1.08 during pregnancy.
• The larger values are abnormal and termination may be considered after 35-37 weeks of pregnancy.

Comment
I think PI MCA/ PI umbilical artery is more reliable than PI MCA / PI Aorta

Reverse flow in the umbilical artery, along with pathologic waveform in the venous system are the best predictor of severe fetal distress, so termination of pregnancy must be considered as soon as possible.

Comment

It must be stressed that:

Delivered fetus with mild fetal hypoxia (only PI of MCA is lower than 1.5) has normal condition and apgar in the labor room, but in future it has higher risk for mean IQ be lower than non hypoxemic fetuses.

  Fetal biometry and arterial Doppler
- the early compensatory phase of IUGR

Venous Doppler, FHR analysis, and the biophysical profile
- data on the later stages (commonly associated with fetal acidosis and impending cardiovascular collapse)

When used in conjunction with other diagnostic tools, Doppler U/S improve outcomes in growth-restricted fetuses