Transmission of electric and magnetic foetal cardiac signals in a case of ectopia cordis: the dominant role of the vernix caseosa

Foetal electrocardiograms (fECGs) and foetal magnetocardiograms (fMCGs) wer e recorded in the 26th, 29th and 31st weeks of gestation from a foetus with ectopia cordis-a rare condition in which the heart lies outside the chest wall. This provided an opportunity to study foetal cardiograms uninfluenced by the insulating effects of the foetal skin and vernix caseosa. The fECG of the ectopia cordis foetus was striking. Unlike recordings from age-match ed normal foetuses, recordings from this subject had very high signal-to-no ise ratio and showed no anomalous signal transmission properties, In contra st, fMCGs recorded from the ectopia cordis foetus and normal foetuses were largely similar. Both showed high signal-to-noise ratio and signal transmis sion properties consistent with volume conduction. The findings corroborate the hypothesis that high foetal skin resistance due primarily to the verni x caseosa is responsible for the low amplitude and anomalous transmission p roperties of the normal fECG, and demonstrate that the fMCG is relatively i nsensitive to conductivity inhomogeneities.