Clinical impact of Doppler reference charts to manage fetal growth restriction: need for standardization.

OBJECTIVE: To assess clinical variability in the management of fetal growth restriction according to published Doppler reference values for the umbilical artery (UA), middle cerebral artery (MCA) and cerebroplacental ratio (CPR).

METHODS: We performed a systematic search of MEDLINE, EMBASE, CINAHL, and the Web of Science databases between the years 1954 and 2018, and selected studies with the sole aim of creating fetal Doppler reference values for the UA, MCA and CPR. Variations between clinically relevant pulsatility index (PI) cut-off values were assessed. Simulation analysis was performed on a cohort of small-for-gestational-age (SGA) fetuses (n=617) to evaluate the impact of this variability on clinical management.

RESULTS: The 10 most cited articles for each index (UA-PI, MCA-PI and CPR) from a total of 40 studies that met the inclusion criteria were analyzed. Wide discrepancies in reported Doppler reference values were found. MCA-PI showed the greatest variability in clinically relevant cut-off values (MCA-PI<5th ) of up to 51% at term. However, the differences between the UA-PI (UA-PI>95th ) and CPR (CPR <5th centile) cut-off values at each gestational age were from 20-40% and 15-35%, respectively. As expected by a simulation analysis, these differences showed great variability in the clinical management of SGA fetuses despite using the same protocol.

CONCLUSIONS: Selection of Doppler reference values can result in significant variability in the clinical management of intrauterine growth-restricted fetuses that may lead to suboptimal outcomes and inaccurate research conclusions. Therefore, an attempt to standardize fetal Doppler reference ranges is mandatory. This article is protected by copyright. All rights reserved.