Development of fetal cardiac intervals throughout 16 to 41 weeks of gestation

In this paper a new noninvasive method is proposed for automated estimation of fetal cardiac intervals from Doppler Ultrasound (DUS) signal and fetal electrocardiogram (fECG) as a reference. The proposed method is based on a combination of Wavelet analysis and hybrid Support Vector Machines- Hidden Markov Models (SVM/HMM). This method provides automated beat by beat identification of cardiac valves´ opening and closing which are used to estimate the fetal cardiac intervals. The range of these intervals in different gestational age from 16 to 41 weeks was evaluated in this study. The correlation between beat to beat intervals was also investigated. Results show a significant negative correlation between Pre-Ejection Period (PEP) and Ventricular Ejection Time (VET) (r = -0.61, p <;0.0001), a positive correlation between VET and Systolic Time Interval (STI) (r =0.51, p <;0.0001) and a significant correlation between PEP and Isovolumic Contraction Time (ICT) (r =0.67, p <;0.0001).