Reference range for tissue oxygen saturation in pregnancy using near-infrared spectroscopy

To estimate the reference range of tissue oxygen saturation (StO2) values in pregnancy. Near-infrared spectroscopy-derived StO2 is a noninvasive continuous measure used to predict hypoperfusion. Normal StO2 values have not been established in pregnant women.

We enrolled 154 healthy pregnant women from an obstetric and gynecology resident clinic. Three sequential measurements were taken after securing the StO2 probe to the thenar eminence of one hand. One-way ANOVA was used to test for differences between trimesters and non-parametric methods to establish a reference range with 95% CI on the limits.

The reference interval for the entire cohort of pregnant women is 73% (95% CI 72-75) to 92% (95% CI 89-93), similar to the normal range in the general population. We found no statistically significant difference in StO2 measurements between trimesters. Due to inadequate sample sizes we could not estimate a valid reference range for each trimester.

We estimated a reference range for StO2 values in normal pregnant women. This information may contribute to the study of StO2 monitoring to predict impending shock in the obstetric patient.