Aim: To investigate the reference values of Doppler indices for umbilical artery and Middle Cerebral Artery as well as Cerebro-placental Ratio and specifically, to evaluate the quality of methodology used on which these reference values are grounded, with the help of already established quality standards for research design, statistical analysis as well as methods of results reporting.

Methodology: The methodological quality of the full-text versions of eligible studies was assessed independently by the same reviewers and a medical statistician (E.S.U.). Disagreements were resolved by consensus or consultation with two other reviewers (A.T.P. and E.F.). Quality criteria for evaluation methodologies of the published articles was developed which was based on the already available research publication25,36,37. The methodology evaluation criteria was segregated into two levels, one is study design and the other one is statistics used as well as its reporting methods. Total no. of criteria of quality were 24 to be evaluated.

Results: Generally, methodological quality score was parallel for the research articles designed to evaluate umbilical artery range (median 42%; range 13.8–63.8%). For the studies focusing on middle cerebral artery range showed a median of 48% with a Class interval of 22.1–72.1% whereas the median score of cerebroplacental ratio was 47.1% with a Class interval of 34.6–55.5%.

Conclusion: Rigorous methodology of this review study is the major strength, which is consisted of a standard and well developed methodology of scoring the quality of studies according to their methodology selection as well as the statistical analysis and the level of its interpretation.

Keywords: Umbilical artery, Middle Cerebral Artery, Cerebro-placental Ratio, Doppler indices