Physiology-based interpretation of CTG reflects a journey back to the very foundation of clinical medicine taught in the first few years of medical school. This includes taking a good history, performing relevant clinical examination and investigations to arrive at a diagnosis (or a differential diagnosis), and then formulating an individualized management plan based on the diagnosis. Obstetric and medical history is the most crucial aspect of physiological interpretation of CTG traces which would entail scrutiny of the CTG trace for specific features to ensure timely and appropriate interventions. Clinical examination is vital as derangements of the maternal environment (e.g. pyrexia, hypoxia, dehydration, ketoacidosis, hypotension, abruption) may result in specific fetal heart rate changes. Timely and appropriate management depends on the specific diagnosis, and this invidualization of care is the key principle of physiology-based CTG training and interpretation. Therefore, it differs from most CTG guidelines that treat all human fetuses the same by recommending the same management for ‘suspicious’ or ‘pathological’ CTG traces.

It is very much hoped that this book, which has moved away from the illogical, unscientific and potentially dangerous ‘nNormal, suspicious, pathological’ classification from its first publication in 2017, and is based on the principles of physiological interpretation of CTG, in line with the International Expert Consensus Statement published by more than 50 CTG experts from over 20 countries in 2024, will continue our journey to reduce avoidable harm to women, birthing people, their babies and the families. We owe this to women, birthing people, their babies and families who have placed in their trust in us to provide evidence-based clinical care, which is based on scientific foundations and the application of the knowledge of fetal pathophysiology.