Estimation of fetal oxygen uptake in human term pregnancies

Abstract

Objective. Umbilical oxygen (O₂) uptake is a parameter of basic physiologic interest. It has been extensively studied in chronically catheterized animals but very few data have been obtained acutely in humans. Recent developments in ultrasound technology allow the estimation of umbilical venous blood flow in utero.

Methods. In all, 26 normal term pregnancies were studied at the time of elective cesarean section in order to evaluate fetal O₂ uptake as the product of umbilical blood flow and umbilical O₂ veno-arterial difference. An ultrasound evaluation was performed within 1 h from delivery: umbilical vein area and flow velocity were recorded to calculate umbilical vein volume flow (Q_umb). Blood samples from the umbilical vein (uv) and artery (ua) were obtained at the time of fetal extraction for respiratory gases and acid–base evaluation.

Results. Umbilical O₂ uptake was calculated as Q_umb • (uv-ua)O₂ content: an average value of 0.84 ± 0.40 mmol/min was obtained. Umbilical O₂ uptake per kg was 0.25 ± 0.12 mmol/kg/min, significantly related to fetal O₂ delivery.

Conclusions. We estimated umbilical blood flow by ultrasound and we measured umbilical O₂ uptake at term obtaining a value of umbilical O₂ uptake/kg similar to what previously reported in human pregnancies and chronically catheterized animals.

Keywords::

• Fetal oxygenation
• umbilical doppler ultrasound
• umbilical vein blood flow
• fetal oxygen delivery
• fetal oxygen extraction

Acknowledgments

This research was supported by A.S.M., CARIPLO (being Dr Cozzi Veronica a recipient of a Cariplo fellowship) and by EU R&D Project Pregenesys (# 037244). The authors are grateful to Giorgio Pardi for the scientific design and strong interest in this study and for his continuous mentoring.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.