Evidence-based fetal assessment

Antepartum cardiotocography (CTG) is the most frequently used method for fetal surveillance during labor. In highrisk-pregnancies antepartum fetal heart rate assessment can be used to predict fetal compromise. However, the false-positive rate can be as high as 60 % for various reasons. Higher sensitivity might be achieved either by longer recording (fetal deep sleep phase) or by adding ultrasound Doppler. Another approach would be to quantify single parameters to determine a score. Extensive knowledge of the physiology and pathophysiology of the fetal cardiovascular regulation is essential for correct interpretation of fetal heart rate patterns.The preliminary warning by CTG for fetal decompensation is with 0-3 days, very short. Therefore, additive methods (Doppler ultrasound, amniotic fluid volume, kineto-CTG) for better preliminary warning should be used for high-risk pregnancies. Continuous electronic fetal heart rate monitoring during labor leads to a significant reduction in perinatal mortality due to fetal hypoxia and neonatal morbidity (neonatal seizures). However, it is also associated with an increase in operative deliveries. Errors of judgement can be reduced by teaching programs for intrapartum fetal monitoring, standardization of the criteria of quantitative design, and defining the need for action by non-reassuring CTG. Using fetal blood analysis (FBA) in labor following non-reassuring CTG may reduce the high false-positive rate of fetal heart rate patterns.The use of CTG in combination with FBA leads to a reduction of avoidable operative deliveries.The development of online-analysis of fetal heart rate patterns with quantification of the parameters by electronic systems leads to a more reproducible interpretation.The implementation of such systems is recommended.The effectiveness of additive methods for fetal monitoring during labor, fetal pulse oximetry with continuous information about oxygen saturation, and ST-waveform analysis of fetal ECG warning in cases of fetal hypoxia and metabolic acidosis, are currently being evaluated in clinical trials. Introduction Antepartum cardiotocography (CTG) provides information on the prevailing status of fetal oxygen supply.The monitoring of fetal heart signals, and their electronic processing and recording as fetal heart frequency (cardiogram), were introduced in the middle of the 1960s.The procedure was then enhanced by the recording of uterine contractions (cardiotocogram).The CTG was quickly put to use for surveillance of the unborn child, replacing sporadic auscultation of the fetal heart beat. CTG recording enabled impressive monitoring of alterations in fetal heart frequency (FHR) during contractions and movements of the child, thus providing reliable documentation for the first time. The initial aim was, and still is, to recognize conditions that present a potential risk to the fetus at an early stage, and to take appropriate action before fetal damage occurs.The main target is to recognize heart frequency patterns associated with deficient fetal oxygen supply.The main problem in CTG monitoring with regard to this target is that heart patterns that are very often classified as pathological correspond to physiological alterations. As a result of such false-positive CTG assessments, the numbers of induced births and operative deliveries have increased.The main causes of misinterpretation are insufficient knowledge of the fetal physiological behavioral conditions and influences depending on gestational age, inadequate training in CTG assessment, and the lack of use of additional diagnostics to assess fetal well-being.The accepted advantage of CTG tracing is that if heart frequency patterns are normal, it can be assumed that the fetus is in a good condition. Fetal oxygen supply is controlled, under physiological conditions, via neuronal regulation of the heart, under the superordinate influence of the medullary centers, which are regulated by pressoand chemoreceptors as well as by local metabolic processes. Various disruptive factors and influences, which may be of maternal, fetoplacental, fetal or exogenous origin, cause alterations in the FHR, such as accelerations, decelerations, variability, tachycardia, and bradycardia. Any assessment of these very complex fetal reactions must take all facets of such influences into consideration. Misinterpretation of FHR patterns can only be reduced to a minimum by intensive instruction and training, accompanied by constant reference to the results of fetal monitoring.