Reference ranges for the intra-amniotic umbilical cord vein diameter, peak velocity and blood flow in a regional NSW population

Aim: To construct gestational age (GA)-related reference ranges of the intra-amniotic umbilical cord vein (UCV) diameter, peak velocity (PV) and blood flow (Qucv) using a Central West New South Wales population.
Materials and Methods: This was a prospective, quasi-experimental study of low risk, singleton pregnancies (n = 321) between 16 and 42 weeks of gestation. Participation was voluntary following informed consent. The UCV diameter and PV were measured using B mode and duplex Doppler respectively, and Qucv calculated. Percentile values and reference range graphs were established using quantile regression modelling in R statistical software. Intraclass correlation coefficients (ICCs) were calculated to assess the intra and intersonographer reliability.
Results: Reference ranges for the UCV diameter, PV and Qucv were established and graphed. All three UCV measurements increased with advancing GA, with both diameter and Qucv exhibiting a decline in the late third trimester. The intrasonographer and intersonographer ICCs for the UCV diameter and PV showed almost perfect agreement within and between sonographers. Conclusion: Gestational age-related reference ranges for the UCV diameter, PV and Qucv were developed using quantile regression from a cohort of low risk, singleton pregnancies in Central West NSW. These reference ranges have the potential to assist in the diagnosis and monitoring of fetal growth restriction.