Nonlinear Analysis of Biomagnetic Signals Recorded from Uterine Arteries.

> Objective: To investigate the hemodynamics of uteroplacental circulation in normal and preeclamptic pregnancies using the biomagnetometer SQUID. Methods: Fifteen pregnancies complicated with preeclampsia and 37 normal pregnancies were included in this study. All women were near term. The biomagnetic signals (waveforms) were recorded with the SQUID from the uterine arteries in normal and preeclamptic pregnancies. Using nonlinear analysis we attempted to differentiate these two types of magnetic activity. Results: Applying nonlinear analysis to the biomagnetic activity recorded from the uterine arteries in preeclamptic pregnancies and using dimensionality calculations we observed a clear saturation value for the preeclamptic pregnancies and nonsaturation for the normal pregnancies. These findings were statistically significant and were correlated with fetal heart rate monitoring, pH, and the Apgar score at 1 and 5 min. High amplitude cases were related to normal fetal heart rate patterns, pH > 7.25, and an Apgar score > 7; low amplitude recordings correlated with abnormal fetal heart rate patterns, pH < 7.25, and an Apgar score < 7. Conclusions: It is suggested that biomagnetic measurements with the SQUID in the uterine artery flow and the application of nonlinear analysis are promising procedures in assessing fetal health, especially in high risk pregnancies.