Simultaneous acquisition of maternal and dual‐fetal electrocardiography with maternal haemodynamic monitoring in anaesthetized pregnant rats

Experimental approaches that acquire maternal haemodynamics together with direct cardiac signals from more than one fetus remain limited. We developed a standardized in vivo method for simultaneous acquisition of maternal ECG, maternal arterial blood pressure and ECGs from two fetuses in anaesthetized late-gestation Sprague-Dawley rats. The platform combines custom-fabricated needle electrodes with conventional cardiovascular instrumentation and PowerLab/LabChart acquisition. Stable, analysable maternal arterial blood pressure, maternal ECG and dual-fetal ECG were maintained for ≤5 h. The recordings supported beat-to-beat ECG interval and heart rate variability analyses. Fetuses had lower heart rates and longer R-R intervals than dams, and fetal root mean square of successive differences (RMSSD), high-frequency power and standard deviation of RR intervals (SDRR) were lower than maternal values. As proof of recording responsiveness, maternal noradrenaline and verapamil administration produced readily resolved maternal haemodynamic changes together with time-aligned fetal heart rate responses. This protocol does not by itself demonstrate maternal-fetal cardiac coupling; rather, it provides synchronized high-resolution signals suitable for future analyses of dynamic maternal-fetal cardiovascular relationships and pharmacological responses.