Normal ranges for fetal electrocardiogram values for the healthy fetus of 18–24 weeks of gestation: a prospective cohort study

Abstract

BackgroundThe fetal anomaly ultrasound only detects 65 to 81 % of the patients with congenital heart disease, making it the most common structural fetal anomaly of which a significant part is missed during prenatal life. Therefore, we need a reliable non-invasive diagnostic method which improves the predictive value for congenital heart diseases early in pregnancy. Fetal electrocardiography could be this desired diagnostic method. There are multiple technical challenges to overcome in the conduction of the fetal electrocardiogram. In addition, interpretation is difficult due to the organisation of the fetal circulation in utero. We want to establish the normal ranges and values of the fetal electrocardiogram parameters in healthy fetuses of 18 to 24 weeks of gestation.Methods/DesignWomen with an uneventful singleton pregnancy between 18 and 24 weeks of gestation are asked to participate in this prospective cohort study. A certified and experienced sonographist performs the fetal anomaly scan. Subsequently, a fetal electrocardiogram recording is performed using dedicated signal processing methods. Measurements are performed at two institutes. We will include 300 participants to determine the normal values and 95 % confidence intervals of the fetal electrocardiogram parameters in a healthy fetus. We will evaluate the fetal heart rate, segment intervals, normalised amplitude and the fetal heart axis. Three months postpartum, we will evaluate if a newborn is healthy through a questionnaire.DiscussionFetal electrocardiography could be a promising tool in the screening program for congenital heart diseases. The electrocardiogram is a depiction of the intimate relationship between the cardiac nerve conduction pathways and the structural morphology of the fetal heart, and therefore particularly suitable for the detection of secondary effects due to a congenital heart disease (hypotrophy, hypertrophy and conduction interruption).

Feasibility of non-invasive Foetal electrocardiography in a twin pregnancy

“…A foetus in cephalic orientation should have a vectorcardiogram that is rotated by 180 degrees compared to a foetus in breech presentation. Assuming both twins to have a normal vectorcardiogram with normal electrical heart axis the orientation of the foetus within the uterus can be estimated [14,15]. This estimation was blinded from the orientations that were determined by ultrasonic examination during the measurement.…”

Enhancement of low-quality fetal electrocardiogram based on time-sequenced adaptive filtering

“…The sequence number at each regeneration time is (re)set to 1 and increases by 1 for each data sample. Since the fetal PR interval is approximately 100 ms [ 37 ], the regeneration times are chosen to occur 160 ms before the detected R peaks. In such a way, the start of the sequence occurs before the P wave starts.…”

Deep Convolutional Encoder-Decoder Framework for Fetal ECG Signal Denoising

“…The signals are denoised and resampled at half frequency to resemble fetal ECG. Afterwards, noise is added to the signals using a set of abdominal measurements of an ongoing study of which the study protocol is described in [10]. In some of these measurements, the fetal ECG was impossible to be detected either because of the shielding of the fetus by the vernix caseosa or because some electrodes were far from the fetal heart.…”

“…Finally, the signals are separated in training and test data, ensuring that there is no overlapping between them. The real fetal ECG was recorded on 6 channels by the Nemo Healthcare fetal monitor, operating at 500 Hz sampling rate, as described in [10]. The signals of all datasets were pre-processed before entering the network, either for training or for testing.…”