How maternal position affects umbilical and middle cerebral artery Doppler indices: insights from a scoping review

Background: During pregnancy, the maternal supine position may reduce uterine and placental perfusion due to compression of the aorta and inferior vena cava by the gravid uterus, potentially impairing maternal and fetal oxygenation. Objective: This scoping review aimed to summarize the available evidence on the impact of maternal positioning during ultrasound examinations on fetal Doppler indices of the umbilical artery (UA) and middle cerebral artery (MCA). Methods: Studies were eligible if they included pregnant women undergoing fetal Doppler assessment in at least two different maternal positions and reported outcomes related to UA and/or MCA indices. Only studies published in English in the past 20 years were included. Sources of evidence: A comprehensive literature search was conducted in the PubMed/MEDLINE, Web of Science, and Scopus databases between September and October 2023. Charting methods: Two independent reviewers conducted the initial screening for relevance, with conflicts resolved by consensus or by a third reviewer. Results: Thirteen studies were initially identified. After applying the eligibility criteria, six observational prospective studies were included. These studies assessed changes in UA-PI, MCA-PI, and/or the cerebroplacental ratio (CPR) in response to different maternal positions during Doppler ultrasound. Conclusions: Evidence suggests that maternal positioning during fetal Doppler ultrasound can influence arterial indices, particularly when comparing supine and lateral decubitus positions. However, variability in methodology and small sample sizes limit the generalizability of findings. Further standardized studies are needed to guide clinical recommendations.