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OB ultrasound

33 studies11 challenges

Where is the pregnancy, how old is it, is it well: the questions each image answers, in the order the clinic asks them. Every image opens with how to read it; switch to Practice when you are ready to be tested.

Ultrasound of a fetal trunk at nineteen weeks with dark fluid within the abdomen and skin thickening around the bodyTransabdominal, transverse trunk · 19 weeks

OB ultrasound · Fetal wellbeing

Nineteen-week fetus with fluid collections

Diagnosis

Fetal hydrops (uploader's description: 19-week fetus with hydrops)

Normal against abnormal

The plane, and which way is up

The planes of the anatomy scan and the Doppler waveforms: the umbilical artery in a free loop of cord, the middle cerebral artery, the ductus venosus, and the biometry that plots growth.

Look for, in order

  1. Fluid collections where there should be none: skin oedema, pleural or pericardial effusion, ascites; two or more compartments is hydrops.
  2. Growth against the dates and against the previous scan; the abdominal circumference falls first in placental insufficiency.
  3. Umbilical artery Doppler: is end-diastolic flow present, absent or reversed?
  4. Movements, tone and breathing over time; the fluid volume.

What normal looks like

Growth along its centile, positive end-diastolic flow, a normal fluid pocket and no effusions.

Trap. A single measurement is a size, not growth; growth needs two scans at least two weeks apart.

Describe it in this order

  1. The plane and the approach (transabdominal or transvaginal)
  2. Location of the pregnancy: in the uterus or not
  3. Number: singleton or multiple, and chorionicity
  4. Viability: cardiac activity
  5. Dating or growth: the measurement that fits the stage
  6. Fetal anatomy, placenta, cord, fluid, cervix, as the stage allows
  7. Adnexa and free fluid
  8. Then, and only then, the impression

Findings

  • Fluid within the fetal abdomen (ascites)
  • Skin oedema around the trunk

What it means for the patient

Hydrops is fluid in two or more fetal compartments: skin oedema, ascites, pleural or pericardial effusion, or placental thickening. Immune hydrops follows maternal alloimmunisation; non-immune hydrops has a long list of causes headed by cardiac, chromosomal, infectious (parvovirus) and anaemic ones. The maternal antibody screen and the middle cerebral artery Doppler come first.

Framework: Cunningham et al., Williams Obstetrics, 26th edition (maternal physiology, labour mechanics, placental anatomy) (2022).

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