What should you know about anencephaly on ultrasound?

The examiner views the head from several angles and also checks the spine and other fetal anatomy. A specialist should interpret the full examination because acrania, evolving abnormal brain tissue and other rare conditions can overlap in appearance, particularly early in pregnancy.

Normal skull bones create a bright, continuous outline around the developing brain. With anencephaly, that protective vault is not formed and normal cerebral structures cannot be seen. The face and lower parts of the brain may still be visible. A fetal medicine clinician considers these features together with gestational age rather than diagnosing from a single still image.

An unclear view is not the same as an abnormal result. Fetal position, early timing, abdominal scarring or other technical factors may limit what can be seen. In that situation, the report may recommend another examination to complete the views. Clearly abnormal anatomy, however, warrants timely specialist review.

Keep the written report and ask whether the specialist will have access to the original images. At the appointment, request a plain-language explanation of the skull outline, brain tissue and any other findings. Ask the clinician to separate what is confirmed from what remains uncertain and to explain whether another scan or testing would add useful information.

If anencephaly is confirmed, you should be offered a sensitive discussion of pregnancy options and support services. Decisions do not need to be made while you are still unclear about the findings. A partner, relative, friend or interpreter can join the conversation if you choose.

Contact the maternity team promptly when a report mentions a missing cranial vault, absent skull ossification, exposed brain tissue or suspected anencephaly. Specialist review is needed even if you feel physically well. Separately, obtain urgent assessment for heavy bleeding, severe abdominal pain, fluid leaking from the vagina, fever, fainting, or a significant reduction in fetal movements after a regular pattern has developed.

Useful questions include which skull and brain features were visible, whether the views were technically complete, and how the pregnancy dating affects interpretation. Ask who will confirm the diagnosis, whether other abnormalities were seen, what further testing could clarify, and when you can meet a clinician who can explain pregnancy choices, birth planning and emotional support.