No abstract

The 'classical' concept that pregnancy-induced hypertension (PIH) and pre-eclampsia (PE) primarily originate from defective placentation in early pregnancy has been challenged recently. There is growing evidence that other factors, including maternal predisposing conditions, also play a significant role in the pathophysiology of PIH and PE. The aim of the present study was to test the hypothesis that PIH and PE with an early onset and poor pregnancy outcome is associated with defective placentation, e.g. inadequate spiral artery dilatation and subsequent reduced uteroplacental perfusion, whereas PIH and PE with normal pregnancy outcome is not. Using Doppler ultrasound, we measured the uterine artery pulsatility index (PI) in a population of 531 nulliparous women in the 22nd week of gestation. Uterine artery PI was used as an index of resistance to blood flow in the uteroplacental circulation. Outcome measures were PIH/PE with or without poor pregnancy outcome, preterm birth and intra-uterine growth restriction (IUGR). The results revealed a striking difference between PI values for PIH/PE with and without poor pregnancy outcome. Uterine artery PI in the 22nd week was increased significantly in pregnancies which developed early-onset (before 35 weeks) PIH/PE with a poor pregnancy outcome. In contrast, uterine artery PI values were normal in women who developed PIH/PE, but had a good pregnancy outcome. There was a significant correlation between 22nd week uterine artery PI and subsequent preterm birth or IUGR. Our results indicate that only PIH/PE with poor pregnancy outcome is associated with defective placentation, whereas PIH/PE with good outcome is not. These findings support the concept of heterogeneous causes of hypertensive disorders of pregnancy.

Objective The influence of the location of the sensor on reflectance pulse oximetry during fetal monitoring in labour was investigated using the newborn infant as a model.Methods Seven healthy infants were studied between 19 and 48 hours after term delivery. Recordings of reflectance pulse oximetry were obtained from eight different sites on the infant's head. The relative changes in red to infrared light (WIR) were determined. In pulse oximetry WIR values are converted to arterial oxygen values by means of an empirically derived calibration curve.Results Significantly lower R/IR values were found at the forehead compared with the fontanelle, the parietal and occipital position, and the temporal area. Conversion to oxygen saturation values revealed a difference of up to 13.4% in oxygen saturation between the forehead and the occipital area.Conclusion Assuming that the arterial blood oxygen saturation did not change substantially, our findings indicate that in reflectance pulse oximetry there is no unique relation between WIR and arterial oxygen saturation. The differences in reflectance pulse oximetry at the various sites are explained by differences in optical properties (scattering and absorption) of the tissue underneath the sensor. These will affect the red and infrared light reaching the detectors in a different way, and consequently WIR changes. Because during intrapartum monitoring exact positioning of the sensor on the fetal head is usually impossible, the accuracy of fetal reflectance pulse oximetry is impaired.

The NI offers the possibility to quantify the diastolic notch in uterine artery analysis. Compared to the PI, this does not lead to better predictive values for hypertensive disorders of pregnancy.

Uterine artery screening did significantly predict the recurrence of poor pregnancy outcome due to hypertensive complications in this high-risk group. In contrast, gestational hypertension and preeclampsia with normal pregnancy outcome were not significantly predicted by uterine artery screening.