Solving the Obstetrical Paradox: The FETAL Technique—A Step toward Noninvasive Evaluation of Fetal pH

Every year, about 85 percent of the approximately 5 million births in North America are evaluated with the electronic fetal monitoring (EFM). Clinicians use the EFM as a proxy to assess fetal oxygenation status, fetal well-being, and potential compromise. Despite the widespread use of this technology, neonatal hypoxia and acidosis continue to make up a high proportion of neonatal morbidity at term. Indeed, though the fetal heart rhythm is inextricably linked to fetal acid-base status, EFM has not been shown to reliably predict neonatal pH status nor has it reduced adverse maternal or neonatal outcomes. As a consequence, the high false-positive rate of EFM for predicting adverse neonatal outcomes has led to an increase in the rate of operative vaginal and cesarean delivery, with elevated rates of associated maternal and neonatal morbidity. This fact invariably leads to a paradox we have henceforth defined as the “obstetrical paradox.” Herein, we explore the potential solutions to this paradox and introduce a novel noninvasive technique to assess fetal acid-base status in utero known as the “FETAL technique” (Fourier Evaluation of Tracings and Acidosis in Labour). The FETAL technique, currently under investigation, applies the discrete Fourier transformation to EFM tracings to determine the spectral frequency distribution of the fetal heart rate. These specific frequency distributions correlate with specific umbilical pH values and may provide the missing link between fetal heat rate patterns and acid-base status at birth. As we work toward realizing the full potential benefits of EFM, finding the best assessment strategies to evaluate fetal pH in real time remains a key goal in obstetrics.

Fetal cerebral-umbilical Doppler ratio in prediction of fetal distress in patients with preeclampsia

Bacground/Aim. The use of color Doppler ultrasonography provides noninvasive observation, confirmation and quantification of pathophysiological processes in fetoplacental circulation in pregnant patients. By blood vessel mapping and the obtained waves spectral analysis it is possible to evaluate vascular resistency of the fetus blood vessels. The aim of the study was to evaluate cerebral-umbilical pulsatility index ratio in fetal circulation in prediction of fetal distress in patients with preeclampsia. Methods. By measurement of pulsatility indices in medial cerebral and umbilical arteries in 400 patients with uncomplicated pregnancy, normal values were calculated for fetuses from 15-40 weeks. In our study group 70 patients with preeclampsia were included. Cerebralumbilical (C/U) ratio was calculated after pulsatility indices in medial cerebral artery and umbilical artery determining by the spectral Doppler analysis of flow velocity waveforms in these vessels. Fetal outcome was analyzed by measurement of the Apgar score at the 5th minute and fetal pH at birth. Results. The mean C/U ratio values in the third trimester of normal pregnancy were between 1.8 and 1.9. The mean C/U ratio values in the patients complicated with preeclampsia were significantly lower comparing to normal pregnancies (ANOVA, p < 0.05). The mean 5th minute Apgar score in the study group was 6.35 ? 1.58, and the mean fetal pH at birth was 7.16 ? 0.15. Linear regression test showed a highly significant correlation between low C/U ratio and fetal pH at birth in patients with preeclampsia (r = 0.49, p < 0.01). Conclusion. The C/U ratio values obtained from spectral Doppler analysis in fetal vessels showed a highly significant correlation with fetal pH at birth in the patients with preeclampsia. The results of our study confirmed the reliability of C/U ratio in estimation of fetal condition in preeclamptic patients. Very low C/U ratio values in patients with preeclampsia indicate that in these fetuses fetal acidosis and fetal distress may be expected.