10/12/2023 0 Comments Normal fetal heart rate at 6 weeks![]() claimed that 20% of term fetuses have signs of neurological depression at birth associated with non-reassuring CTG patterns, compared to 70–80% of preterm fetuses with the same type of FHR tracings. The evidence suggests that non-reassuring CTG tracings are of greater importance for adverse neonatal outcomes in preterm fetuses than in term fetuses. The sympathetic nervous system is activated in situations of stress accordingly, preterm fetuses will have a higher baseline FHR with an apparent reduction in variability, owing to the predominant action of the sympathetic nervous system and lesser opposition from the parasympathetic system. The FHR is regulated by the autonomous nervous system, and during fetal development the sympathetic nervous system develops much earlier than the parasympathetic system, which develops mainly throughout the third trimester. As a result, the classic characteristics of CTG tracings in healthy term fetuses exposed to hypoxic situations may not be observable in preterm fetuses. īecause they are less developed and less mature, preterm fetuses may respond to stress in anomalous ways, giving rise to situations of permanent hypoxia in the fetal brain at threshold values that may be lower than in term fetuses. This makes it imperative to understand these physiological characteristics in order to correctly interpret FHR patterns in preterm fetuses. Many characteristics of CTG tracings depend on gestational age and reflect the degree of development and maturity of regulatory centers in the central nervous system and cardiovascular system. In the particular case of preterm gestations, no clinical practice guidelines are currently available for EFM, and published studies on CTG in preterm fetuses are scarce. However, continuous CTG was associated with an increase in cesarean deliveries and instrumental vaginal births. The authors concluded that CTG during labor is associated with reduced rates of neonatal seizures, but no clear differences in cerebral palsy, infant mortality or other standard measures of neonatal wellbeing. updated a Cochrane review in 2017 in order to evaluate the effectiveness and safety of continuous CTG as a form of electronic fetal monitoring (EFM) for fetal assessment during labor, compared to intermittent monitoring. In an effort to determine the influence of CTG on perinatal outcomes, Alfiveric et al. This means that watchful waiting is advised when a CTG tracing is considered normal, whereas abnormal FHR tracings offer no certainties regarding the hypoxic status of the fetus or possible acidosis. As a tool with high sensitivity but very low specificity, the false positive rate of CTG findings approaches 60%. Conclusions: The main characteristics of FHR tracings changes as gestation proceeds, and it is of fundamental importance to be aware of these changes in order to correctly interpret CTG patterns in preterm fetuses.Ĭardiotocography (CTG) aims to identify fetal heart rate (FHR) patterns that may indicate a risk, so that clinicians can forestall problems with measures intended to improve perinatal outcomes. Transitory increases in FHR are less frequent and become more frequent and increase in amplitude as gestational age increases. Transitory, low-amplitude decelerations are more frequent during the second trimester. Heart rate is faster in more immature fetuses, and variability is lower and increases in more mature fetuses. Results: Compared to term fetuses, preterm fetuses have a slightly higher baseline FHR. Materials and Methods: A MEDLINE search was carried out, and the published articles thus identified were reviewed. The aims of this narrative review were to summarize the most relevant concepts in the field of CTG interpretation in preterm fetuses, and to provide a practical approach that can be useful in clinical practice. The lack of reference standards for CTG patterns in preterm fetuses can lead to misinterpretation of the changes observed in electronic fetal monitoring (EFM). A review of the available literature on fetal heart rate (FHR) monitoring in preterm fetuses shows that studies are scarce, and the evidence thus far is unclear. ![]() One tool frequently used to determine the degree of fetal wellbeing is cardiotocography (CTG). Optimizing the management of these pregnancies is of high priority to improve perinatal outcomes. Background and Objectives: Prematurity is currently a serious public health issue worldwide, because of its high associated morbidity and mortality.
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