Many private sonographers are already qualified midwives or radiographers, and dedicated training courses are also available, although this is currently not a legal requirement.
Thompson says mums-to-be should ask a private clinic if their staff have been through a course accredited by the Consortium of Sonographic Education (CASE).
Patients can also carry out other basic checks – asking how long the clinic has been operating, for example, whether it has been registered with the Care Quality Commission (CQC) in England and when it was last inspected by the regulator.
Thompson also suggests checking reviews and asking around for advice and recommendations from friends, family, midwives and GPs.
Individual sonographers can decide to join the Register of Clinical Technologists, external, which the public can then search to see if certain standards have been met but, again, participation is voluntary.
The Professional Standards Authority for Health and Social Care recently carried out a public interest test of that register and has written to the government to say the “risks appear sufficiently high” that it should consider if stronger regulation of sonographers may be needed.
The CQC said many clinics were providing good quality care, but it “remains concerned that some are not” with worries over staff training, consent policies and procedures for escalating unusual findings.
Where its inspections identify concerns it said it would “hold providers to account and make clear that action is required to ensure staff are adequately trained”.
In a statement, the Department of Health said the safety of patients was paramount and the regulation of all healthcare professionals was kept under review.
“We will carefully consider any proposals from professional bodies regarding this,” added a spokesman.