doppler in iugr

Role of doppler in Intrauterine growth retardation

Presented byDr. Sandeep Garg (Resident)

Department of RadiodiagnosisCMS

3rd Nov, 2011

25 yrs female with 30 wks of POG and uncontrolled hypertension was referred from gynae/obsc dept for doppler.

USG and doppler findings include◦ >HC/AC ratio 1.32◦ Severe oligohydraminos (AFI 3 cm)◦ MCA PI 1.27◦ UA PI 1.39◦ MCA/UA PI ratio – 0.91

Impression: fetal hypoxia/ IUGR

IUGR: fetus with birth weight <10th percentile for gestational age due to pathologic process.

SGA: fetus with birth weight <10th percentile for gestational age in the absence of pathologic process

IUGR-definition

Aetiology

Maternal Fetal Placental

Constitutional Cong anomalies Abn Trophoblast Nutritional Chromosomal Velamentous cord Genetic Infections Circumvallate p Collagen vascular ds Multiple preg Pl Praevia Autoimmune disease Pl infarction HTN, Diabetes Tumors Renal disease Environmental

Symmetrical : Uniformly small, HC:AC,FL:AC-Normal seen in chromosomal anomalies

Asymmetrical : fetal abdomen is disproportionately small (Head sparing effect)

HC>AC HC:AC, FL:AC-Elevated

Types of IUGR

elevated HC/AC ratio (positive predictive value 62%)

elevated ratio of femur length to abdominal circumference (FL/AC)

presence of oligohydramnios without ruptured membranes

presence of advanced placental grade (Grannum grade 3)

Sonographic Criteria for Diagnosing IUGR

Fetal biophysical profile

Typically, scores of 6 or below are considered frankly abnormal, and scores of 7 and 8 are considered suspicious.

Reduced biophysical profile scores are found in growth restricted pregnancies that already demonstrate abnormal umbilical and fetal Doppler findings.

Fetal biophysical profile

Most of these fetuses are constitutionally small, and are not suffering from uteroplacental insufficiency.

An inter-twin growth discrepancy of 20–25% is considered to be significant.

Twin-to-twin transfusion syndrome (TTTS)- Color Doppler findings in the donor are usually typical of uteroplacental insufficiency

Growth in Multiple pregnancy

Doppler waveform analysisQuantitative analysis

◦ Pulsatility index (PI)◦ Resistance index (RI)◦ Systolic/diastolic ratio

Qualitative analysis◦ Uterine artery: presence

or absence of early diastolic notch

◦ UA : normal, with reduced diastolic flow, absent EDF, reversed EDF

Uterine arteries branch into arcuate arteries, leading to spiral arteries within myometrium.

With advancing pregnancy, due to trophoblastic invasion of uterine spiral arteries, it dilates and result in fall in resistance to blood flow.

Uterine blood flow in non pregnant women is 50 ml/min and increase to over 700 ml/min in 3rd trimester.

Hence, in normal pregnancy diastolic component is transformed from one of low peak flow velocity and early diastolic notch , to one of high flow and no diastolic notch by 18 to 22 wks, PI value <1.2

PI >1.45 with bilateral notches (abnormal) is s/o clinically significant uteroplacental vascular ischaemia.

Doppler of Uterine arteries(uteroplacental waveform)

Normal uterine artery at 22 wks gestation

IUGR at 26 wks gestation

Characteristic umbilical artery waveforms have also been correlated to various degrees of fetal hypoxemia and acidemia.

Absent end-diastolic frequencies◦ 75% of the placental vascular bed has been

obliterated◦ 85% chance that the fetus will be hypoxemic

and a 50% chance that it will also be acidemic. Reversed end-diastolic frequencies

◦ ten-fold increase in perinatal mortality

Umbilical artery doppler

Doppler umbilical artery

Pulsatility index of umbilical artery

Fetal arterial waveforms are acquired from the thoracic aorta and middle cerebral arteries.

With fetal hypoxemia, there is conservation (or increase) of blood flow to the fetal brain, heart and adrenal glands with concomitant decrease in flow to the splanchnic bed and extremities. This phenomenon is termed ‘arterial redistribution of blood flow’, and serves to deliver oxygen and nutrients to vital organs in the face of impaired placental function.

Hence, fetal arterial Dopplers can be used to monitor fetal compensatory responses to progressively deteriorating placental function.

Fetal arterial doppler

MCA can be easily demonstrated by color doppler in transverese fetal head position.

At 28-32 wks, MCA is characterized by high systolic velocities and minimal diastolic velocities, resulting in high PI values (>1.45).

In fetal hypoxia, vascular tone is increased in MCA resulting in increased diastolic velocity and reduced PI values.

Fetal middle cerebral artery

MCA location

NormalIUGR

With hypoxia there is cerebral vasodilatation, so initially the diastolic flow may be in the normal range ,when the vasodilatation ability is exhausted as with fetal acidosis the resistance starts increasing again.

Fetal thoracic aorta A longitudinal view of

the fetal thoracic aorta is obtained with color flow imaging.

The pulsed Doppler sample gate should be placed on the linear portion of the descending thoracic aorta, above the level of the diaphragm

The ductus venosus is the main vessel through which oxygenated blood returning from the placenta is directed to the fetal heart and circulation.

With worsening fetal hypoxemia, abnormal umbilical artery waveforms and severe fetal arterial redistribution develop.

In addition, there is also increased redistribution of highly oxygenated umbilical vein blood through the ductus venosus to the fetal heart.

When the fetal condition becomes critical, abnormal ductus venosus flow waveforms are seen.

Fetal venous doppler

Ductus venosus location

Ductus venosus waveform

Normal Abnormal

Biometry◦ EFW 640 g (<10th centile)◦ HC/AC ratio 1.35 (normal <1.2)◦ AFI 7 cm (normal 10-20 cm)

Doppler◦ Uterine arteries- B/L early diastolic notch◦ Lt uterine artery PI 1.97, Rt PI 1.65◦ UA- absent EDF in both◦ Smooth umbilical venous cord flow, peak vel 16cm/sec◦ MCA- PI 1.12 (redistribution)◦ Ductus venosus – positive A wave 32 cm/sec (normal)

Biophysical profile score- 8/8 normal Anatomic evaluation- short femurs, mildly

echogenic bowel

USG findings in Early onset severe IUGR at 28 wks

Gramellini et al (1992) studied that in 30-41 wks POG, MCA/UA PI ratio (cerebro-umbilical flow) <1.08 is better predictor of fetal insufficiency than MCA PI or UA PI alone. Diagnostic accuracy for the cerebral-umbilical ratio was 90%, compared with 78.8% for the middle cerebral artery and 83.3% for the umbilical artery.

MCA doppler and fetal anaemia

1990 G.Mari proposed the use of MCA dopplers for the diagnosis of anemia

The sensitivity of the peak systolic velocity for the prediction of moderate anemia and severe anemia in the fetuses without hydrops was 100 percent , with a false positive rate of 12 percent. The positive and negative predictive values were 65 percent and 100 percent, respectively.

The risk of anemia was high in fetuses with a peak systolic velocity of 1.50 times the median or higher. Fetuses with values below 1.50 either did not have anemia or had only mild anemia.

the MCA PSV is effective for accurate diagnosis of fetal anemia and can avoid about 70% of invasive procedures.

Thank you