URR GYN 2D and Doppler Assessment in the 2nd/3rd Trimester

Where do you measure BPD?

At level of third ventricle, cavum septum pellucidum and thalamus

How do you measure BPD?

Widest part of skull from leading edge to leading edge of parietal bones

What is the most accurate biometric measurements for dating before 20 weeks?

Corrected BPD and HC

Where do you measure AC?

At level of portal vein and stomach with a single rib on each side

When can Femur length reliably be used?

After 14 weeks gestation

What does a proper femur length include?

Ossified diaphysis (not epiphyseal cartilage)

When attempting to assess interval growth, the optimal time for the follow up exam is?

An interval of 3 weeks

What is the least accurate as a predictor of age after 33 weeks?

BPD

What is corrected BPD formula?

BPDc = square of (BPD x OFD / 1.265)

Head Circumference should NEVER include?

Scalp/skin thickness

How to measure OFD?

From anterior skull to posterior skull on outer edges of cranium

What is normal measurements for Cephalic Index?

0.70 - 0.85

Cephalic index formula?

BPD/OFD x 100%

Measurement of Dolichocephaly?

CI <0.70

What is Dolichocephaly?

Elongated head, BPD shortened

Measurement for Brachycephaly?

CI >0.85

What is Brachyecphaly?

Rounded head, BPD elongated

Normal limit of Lateral ventricles?

<10 mm

How to measure Lateral ventricles?

Inner diameter of posterior ventricular horns

How to measure Cisterna Magna?

Measure largest AP diameter of the cavity posterior to cerebellum

Normal measurement of Cisterna Magna?

<10 mm

Label the Superior Intracranial Anatomy

1. Choroid Plexus

2. Lateral Ventricle

3. Falx Cerebri

Label the BPD intracranial anatomy

1. Thalamus

2. CSP

3. 3rd Ventricle

Label the Inferior Intracranial Anatomy

1. Cerebellum

2. Cisterna Magna

3. Hypothalamus

What Intracranial measurement is consistently with the week of gestation in millimeters?

Cerebellum

How to measure Nuchal Translucency?

Inner to inner dimension

Normal measurement for NT at 11-14 weeks?

<3 mm

Normal measurement of NSF at 15-21 weeks?

< 6mm

What should be documented with the Umbilical cord?

Cord insertion (abdominal and placental)

How are foot measurements taken?

From longest toe to tip of the heel

What part of the hand is measured when Trisomy 21 is suspected?

Middle phalanx of the 5th digit

Normal Ratio of HC/AC?

0.87-1.33

Normal ratio range of BPD/FL?

71 - 87%

Normal ratio range of FL/AC?

20 - 24%

Normal Ration range of CI?

70-85%

What is the most variable fetal measurement?

AC

Higher HC/AC and FL/AC ratios can indicate?

Asymmetric IUGR

Higher BPD/FL ratios can indicate?

Trisomy 21 or achondroplasia

Low CI values =

Dolichocephaly

High CI value =

Brachycephaly

Binocular diameter?

Outer to outer edge of orbits

Interocular diameter?

Inner to inner edge of orbits

Fetal MRI is preferred after?

22 weeks

The thalamic view is used to obtain what measurement?

BPD, OFD, HC

Formula for S/D ratio?

PSV / EDV

RI calculation?

PSV - EDV / PSV

Pulsatility Index calculation?

PSV - EDV / Mean flow velocity

What is the most common method for diagnosing fetal anemia?

PW Doppler of the MCA

Where should the MCA be sampled for PW Doppler?

Anterior to the thalamus and as close to the origin from the ICA as possible

What does IUGR do to the vessels in the circle of wills?

Significant increase in antegrade diastolic flow

Where should samples be taken of the Ductus Venosus?

At origin adjacent to the umbilical vein and at the junction with the IVC near the heart

Where are the uterine arteries best evaluated?

Level of the cervix

What is a characteristic sign of increased resistance to flow in the uterine arteries?

Early diastolic notching

Why is flow in the umbilical arteries evaluated?

Signs of placental insufficiency

What S/D ratio after 30 weeks of gestation is abnormal?

>3.0

What should the flow look like in the Umbilical Vein?

Continuous and non-pulsatile throughout pregnancy

Pulsatile flow in the umbilical vein later in pregnancy can indicate?

Congestive heart failure

Where should the fetal descending aorta be sampled at?

Level of the fetal diaphragm

Where should the sample of the fetal IVC be taken?

Proximal to the junction with the right atrium

What happens in the IVC with fetal hypoxia?

Pulsatility increases

What does IUGR cause in the umbilical artery?

Decreased or absent flow

What is head sparing?

Decreased PI in the MCA due to IUGR

What is Systemic Lupus Erythematosus associated with?

IUGR, pre-eclampsia and prenatal death

What does systemic Lupus erythematosus do to flow in the umbilical arteries?

Increased Resistance

What does fetal anemia do to MCA, descending aorta and umbilical vein?

Blood flow velocities increased

With twin pregnancies how are the uterine arteries affected compared to singleton pregnancies?

Flow resistance is lower

What is the preferred maternal position for Doppler evaluation of a fetus?

Semi-recumbent

What two values must be obtained from a Doppler tracing to calculate the resistive and pulsatility index?

Peak systolic and end diastolic velocities

What changes to the Doppler waveform of the ductus venosus occur with anemia and IUGR?

There is diastolic flow reversal during the atrial contraction

What normally increases as the pregnancy progresses?

The amount of antegrade diastolic flow

Pulsatile flow in the umbilical vein later in pregnancy can indicate

Congestive heart failure of the fetus

How is suspected fetal anemia evaluated by Doppler?

Serial evaluations of the MCAs