Résumé
Pregnancy induces changes in the endocrinal and neural regulatory mechanisms affecting the cardiovascular system. The endocrinal manifestations of increased steroid hormone causes volume overload, which ultimately puts stress on the autonomic activity. Orthostatic dysregulation leads to spontaneous abortion, low birth weight infant and still birth. In the orthostatic test, reloading of the baroreceptors causes an increase in the blood pressure along with a rapid decrease in the heart rate within 30 seconds of standing up, which stabilizes by the end of 3 minutes. The haemodynamic changes of increased blood volume, increased cardiac output, decreased peripheral resistance and manifestations of endocrinal functions causing volume overload are maximal in the mid term pregnancy. In our study comparison of 30 mid term pregnant women with an equal number of non pregnant (purposive) control subjects was made by measuring instantaneous increase in heart rate (IIHR); heart rate difference (HRDiff.); orthostatic blood pressure at 30 seconds (OSBP 30); orthostatic blood pressure at the end of 3 minutes (OSBP 3) and Maximum (Max.)/ Minimum (Min.) ratio. The statistical analysis was done by students unpaired ‘t’ test. The percentage difference of Max./Min. ratio among pregnant as compared to non pregnant was significant (p<0.017) though it remained within physiological limits.