The ultrasound approach for the known couple at risk of having a foetus with Hb Bart’s hydrops foetalis is as follows [24, 28]:
The mother should undergo serial foetal ultrasound scans starting from 12–14 weeks of pregnancy. The ultrasound is aimed to identify the pre-hydropic signs in the foetus: (a) an increase in foetal cardiac size, represented by cardio-thoracic diameter ratio: CTR or cardiac circumference; and (b) middle cerebral artery-peak systolic velocity (MCA-PSV). It is also used to identify hydropic signs such as ascites, pleural effusion, or pericardial effusion. It is important to note that MCA-PSV alone may underestimate the degree of tissue hypoxia and fail to identify hydrops early in pregnancy.
Serial ultrasound examination is to be scheduled every 2-4 weeks if there are no pre-hydropic signs.
In cases of absent pre-hydropic signs, serial ultrasound scans can be discontinued after 24 weeks of gestational age. An additional scan before labour may be performed.
If any pre-hydropic or hydropic signs is identified on serial ultrasound examinations, the invasive diagnosis is offered to obtain a definite diagnosis.
