Regarding transabdominal ultrasound of the fetus:

1. (a) Doppler examinations impart less energy when compared with routine ultrasound.

2. (b) 18 to 20 weeks of gestation is the optimal time to confirm intrauterine location.

3. (c) Cardiac activity is seen at 5 weeks' gestational age.

4. (d) Crown rump length is a useful measurement of gestational age at 10 weeks.

5. (e) The fetal pole is discernible before cardiac pulsation.

Concerning ultrasound of the fetus from 18–20 weeks:

1. (a) The BPD is measured in the axial plane.

2. (b) The lateral ventricles are echobright structures.

3. (c) The medial walls of the lateral ventricles are formed by the septum pellucidum.

4. (d) The third ventricle is normally visualized.

5. (e) The cerebellar hemispheres are seen as round echopoor structures with a reflective vermis in the midline.

Regarding the fetus:

1. (a) The vertebra are visible as two ossification centres in the body and one in each lamina.

2. (b) Failure of fusion between the premaxillary part of the frontonasal prominence and the maxillary prominence gives rise to cleft lip.

3. (c) The four-chamber view during cardiac ultrasound is the primary screening view for cardiac abnormalities.

Obstetric anatomy

ANSWERS

1. (a) False – the opposite is true. In general, routine ultrasound is considered completely safe in pregnancy, though examinations should be performed only if clinically indicated and the duration should be kept optimal, particularly when using Doppler.

2. (b) False – it is the first trimester. During the second and third trimester ultrasound is used to estimate gestational age, to detect structural fetal anomalies, fetal lie and presentation and placental position.

3. (c) False – cardiac activity is visible at 5 to 6 weeks on transvaginal scanning and at 7 weeks on transabdominal scanning.

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