OBSTETRICAL CONDITIONS

What is fetal biometry primarily used to assess?

Intrauterine growth retardation

What else does fetal biometry help with?

Diagnosing anomalies

How does the chorionic cavity first appear?

Anechoic, later surrounded by an echogenic rim

When is the gestational sac detectable?

After the 14th day of conception

What is the GSD used for?

An important growth parameter in first-trimester pregnancies

How can gestational sac growth be assessed with improved accuracy?

Sac volume using transvaginal 3D ultrasound

What is the first element seen within the gestational sac?

The yolk sac

How does the yolk sac appear at the 5th gestational week?

Echoic ring-like structure

Yolk sac size by the 10th gestational week?

Increases to about 5 mm

Abnormal yolk sac diameter?

< 3 mm or > 7 mm

What is an abnormal yolk sac size associated with?

Higher risk of developmental anomalies

What does CRL measure?

Length of the baby from the top of the head (crown) to the bottom of the buttocks (rump)

When can CRL be measured?

From about 6 or 7 weeks up to 14 weeks

What is CRL useful for?

Calculating gestational age and estimating the due date

How does timing affect accuracy?

The earlier the first ultrasound, the more accurate the gestational age

CRL unit of measurement

Centimeters

What does BPD measure?

Diameter of the fetal skull, from one parietal bone to the other

What is BPD used to estimate?

Fetal weight and gestational age

When does BPD measurement begin?

12th gestational week

How does the choroid plexus appear?

Bilateral, echogenic structure

Correct orientation for BPD?

Parallel to the midline echo of the falx

What part of the femur is measured?

The ossified femoral diaphysis

Positioning of the upper leg?

As close as possible to the axis of the probe

What does femur length reflect?

Longitudinal growth of the fetus

Femur is which bone in the body?

The longest

FL usefulness compared with what?

Similar to BPD

Femur length at 14 weeks?

1.5 cm

Femur length at term

7.8 cm

What is AC used to assess?

Fetal size (a basic biometric parameter)

Which measurements are combined to estimate fetal weight?

AC, BPD, head circumference, and femur length

Reference plane for AC?

Level of the liver, ideally showing the dorsal third of the umbilical and portal veins

How should the ribs appear?

Bilateral ribs displayed symmetrically (confirms the section was not oblique)

Usual placental position?

Near the fundus of the uterus, along the anterior or posterior wall (top or side)

What is an anterior placenta?

Placenta attached to the front wall of the uterus

What is a posterior placenta?

Placenta attached to the back wall of the uterus, near the spine

What is placenta previa?

Placenta partially or totally covers the mother's cervix