Detection of Weak Foetal Electrocardiograms by Autocorrelation and Crosscorrelation of Envelopes

There is no general rule that abdominally recorded electrocardiograms of pregnant women reveal visible foetal R waves. In some stages of pregnancy the foetal electrocardiogram (FECG) is even smaller than a slightly noisy baseline. It is also possible that large muscle disturbance (electromyogram) makes the FECG invisible. On the one hand, there is a redundancy of information in the form of a long lasting FECG and, on the other hand, the human eye fails to survey this information stream.