Placenta Previa: Who Changed the Definition

Considering that all our Assistant Professors gave varied answers to the question about the distance of the lower edge of the placenta from the internal os to be called previa, I did a survey of a number of postgraduate text books of obstetrics. I realized there was no consensus on what was placenta previa. For unknown reason some books have changed the definition and classification of placenta previa, while a few have stuck to the old definition and types (I to IV). A summary of my findings is as follows. Williams Obstetrics: new classification in the form of total, partial, marginal and low lying (the last one in close proximity to the internal os, but no specific distance), no sonographic criterion for the last type. Obstetric & Gynecologic Emergencies: Pearlman et al: somewhat similar to Williams, but the distance for the last type is < 2 cm. Current Obstetric & Gynecologic Diagnosis and Treatment: 2 cm. Current Clinical Strategies: Chan Johnson: 2 cm. Some books mention that if the edge of the placenta is more than 2 cm from the internal os, there will not be antepartum hemorrhage (e.g. Obstetrics & Gynecology: An Illustrated Color Text: Pitkin et al.) Some books mention that if the edge of the placenta is more than 2 cm from the internal os, there will not be difficulty with vaginal delivery (e.g. Clinical Obstetrics: The Fetus and Mother: Reece – Hobbins.) Obstetrics & Gynecology at a Glance: Norwitz - Schorge: no mention ABC of Antenatal Care: Chamberlain - Morgan: no mention Management of High Risk Pregnancy: An Evidence Based Approach: Queenan Best Practices in Labor & Delivery: Warren - Arulkumaran Anesthetic and Obstetric Management of High-Risk Pregnancy: Sanjay Datta: no mention Clinical Protocols in Obstetrics & Gynecology: Iforma Practical Obstetric Problems: Ian Donald: 3 inches or 7 cm. Unfortunately someone edited this book after Dr Donald passed away and removed all such information and released the book for distribution in our and perhaps nearby countries only. I hope he does not come to know about it, wherever he is (may his soul rest in peace). I found that in some books the sentences in this connection were identical. It is difficult to decide if they copied one single source, or someone copied one book, then someone else copied this copier, and then a chain reaction started. What emerges from all this is that someone made a non-evidence based change, which many copied, and finally the science has changed.