Optimal fetal positioning: a theory in tatters-time to rewrite textbooks.

Abstract

Optimal Fetal Positioning, the theory that engagement of the fetus in left occipito-anterior position is advantageous and that maternal posturing such as hands and knees and left lateral be employed to encourage the fetus into this position, has been preached and practised extensively. Two midwives who impressed me most during my early years as a researcher, set out to test this theory scientifically. The theory had some basic assumptions: one diagnostic (one can tell the position by abdominal palpation) and another prognostic (initial position has a relation to birth outcome). If these could be proven, there would have been hope that the promoted maternal posturing theory could have a beneficial effect. Otherwise they were setting themselves up for criticism for bringing their profession in disrepute, as the theory was held in the greatest regard. In a prospective classical test accuracy study, using ultrasound as a reference standard administered blind to index text, Webb showed that abdominal palpation had poor accuracy for diagnosing position at onset of labour before the cervix was 4 cm dilated at term (Acta Obstet Gynecol Scand 2011;90:1259–66). Soon after this, her colleague Ahmad (Ultrasound Obstet Gynecol 2014;43:176–82), dropped a bombshell: follow up of over 1000 women in labour showed that objectively assessed initial position had no association whatsoever with the likelihood of spontaneous vaginal birth. Bang went the theory. I will be forever grateful to these bold midwives who, regardless of the outcome for themselves and their profession, sought to discover the truth about an entrenched belief using strong research methods. The above findings turned the theory on its head. We could no longer be sure whether what was said in the past (without ultrasound diagnosis of position) was the result of false diagnosis by palpation. We could now tell for sure that any purported link between spontaneous vaginal birth and initial fetal position was merely due to chance. Against this background, where the fundamentals are in question, it is hardly surprising that trials (BJOG 2016; doi 10.1111/1471-0528.13855; Am J Obstet Gynecol 2013;208:60.e1–8; BMJ 2004;328:490) have been negative. Let's get down to researching other more promising subjects and to writing the truth about optimal fetal positioning theories in textbooks. The author is a the BJOG Editor-in-Chief and his disclosure of interest can be found at BJOG.org.