Fetal heart rate measurements of twins using a single flexible transducer matrix

The increased use of assisted reproductive technology and increasing maternal age have led to a significant increase of twin births in Western countries. Twin pregnancies are associated with increased risk for fetal distress and, therefore, monitoring fetal health is crucial. Fetal well-being is typically assessed by measuring the fetal heart rate (fHR) using a Doppler ultrasound (US) transducer. In twin pregnancies, two independent US transducers need to be manually positioned on the maternal abdomen, which requires skill and experience. Common clinical problems are: 1) both hearts lie in the same sample volume (SV) of the same transducer, leading to erroneous fHR registration, 2) the heart locations change due to fetal movement hence moving out of the sample volume, 3) registration of the maternal heart rate and 4) both US transducers aim at the same heart and measure the same fHR. In this study, we propose twin-fHR measurements using a flexible US transducer matrix. The array aperture allows measuring the Doppler power from multiple SVs simultaneously to localize both fetal hearts in 3D. Furthermore, automated Doppler signal clustering enables unambiguous determination of the fHR of both fetuses.