Related Experiment Video
Updated: Jul 7, 2026

Semi-automated Optical Heartbeat Analysis of Small Hearts
Published on: September 16, 2009
Extracting fetal heart signals from Doppler using semi-supervised convolutional neural networks
Yuta Hirono1,2, Chiharu Kai1,3, Akifumi Yoshida3
1Major in Health and Welfare, Graduate School of Niigata University of Health and Welfare, Niigata, Japan.
Insights
Semi-supervised learning improves artificial intelligence (AI) classification of Doppler ultrasound (DUS) signals for fetal monitoring. This AI approach enhances fetal well-being assessment accuracy, even with limited data.
Area of Science:
- Biomedical Engineering
- Artificial Intelligence in Healthcare
- Fetal Monitoring Technologies
Background:
- Cardiotocography (CTG) is vital for fetal well-being assessment, requiring clear Doppler ultrasound (DUS) signals.
- Current fetal heart rate (FHR) algorithms struggle with signal differentiation, leading to monitoring gaps.
- Limited data availability hinders the application of artificial intelligence (AI) for DUS signal classification.
Purpose of the Study:
- To evaluate semi-supervised learning's effectiveness in improving DUS signal classification accuracy.
- To address the challenge of limited data in developing AI models for fetal monitoring.
- To enhance the reliability and accuracy of fetal well-being assessments using AI.
Main Methods:
- Developed an AI model using semi-supervised learning for classifying DUS signals (fetal heartbeat, artifacts, etc.).
- Utilized a dataset comprising 9,600 labeled and 48,000 unlabeled DUS signal data points.
- Compared the performance of the semi-supervised model against a supervised learning model.
Main Results:
- The semi-supervised learning model achieved an average classification accuracy of 80.9%.
- Semi-supervised learning consistently outperformed the supervised learning model in DUS signal classification.
- Demonstrated high generalization accuracy with a limited dataset.
Conclusions:
- Semi-supervised learning is effective in enhancing AI model accuracy for DUS signal classification.
- This AI approach can improve fetal monitoring quality and reduce development effort.
- The findings suggest a promising method for more reliable fetal well-being assessments.
Abstract:
Cardiotocography (CTG) measurements are critical for assessing fetal wellbeing during monitoring, and accurate assessment requires well-traceable CTG signals. The current FHR calculation algorithm, based on autocorrelation to Doppler ultrasound (DUS) signals, often results in periods of loss owing to its inability to differentiate signals. We hypothesized that classifying DUS signals by type could be a solution and proposed that an artificial intelligence (AI)-based approach could be used for classification. However, limited studies have incorporated the use of AI for DUS signals because of the limited data availability. Therefore, this study focused on evaluating the effectiveness of semi-supervised learning in enhancing classification accuracy, even in limited datasets, for DUS signals. Data comprising fetal heartbeat, artifacts, and two other categories were created from non-stress tests and labor DUS signals. With labeled and unlabeled data totaling 9,600 and 48,000 data points, respectively, the semi-supervised learning model consistently outperformed the supervised learning model, achieving an average classification accuracy of 80.9%. The preliminary findings indicate that applying semi-supervised learning to the development of AI models using DUS signals can achieve high generalization accuracy and reduce the effort. This approach may enhance the quality of fetal monitoring.
Related Concept Videos
Assessing Blood pressure using a doppler ultrasound
Pre-Procedural Guidelines for Doppler Ultrasound Blood Pressure Assessment:
Preparation of Equipment:
Fetal Circulation
Two umbilical arteries transport blood from the fetus to the placenta. At the placenta, the blood absorbs oxygen and nutrients while simultaneously eliminating waste products. This oxygen-enriched and nutrient-rich blood then returns to the fetus through one...

