: There is a growing evidence linking the autonomic nervous system with various physiological and pathological states. The changes in heart rate (HR) rely on a balance between the influence of the parasympathetic and the sympathetic branches of the autonomic nervous system (ANS) on the heart. There are few researches on effect of BMI and heart rate variability (HRV). A case-control study (120 participants; 60 preelamptic and 60 control) were conducted at Omdurman Maternity Hospital and Saad Abul Ela Maternity Hospital - Sudan, during the period from June 2015 to December 2016. Medical, obstetrics history and clinical examination were performed to all studied women guided by prearranged questionnaires. Cardiac autonomic modulation (CAM) of the heart was examined in both studies based on HRV indices, namely, the natural logarithm (Ln) of the standard deviation of the NN intervals (LnSDNN), the square root of the mean squared differences of successive NN intervals (LnRMSSD), total power (LnTP), very low frequency (LnVLF), low frequency (LnLF) and high frequency (LnHF). Also, normalized low frequency (LF Norm) and high frequency (HF Norm) and LnLF/HF ratio were measured. The study demonstrated that in the normal weight group, women with preeclampsia had significantly higher LnSDNN, LnVLF and LnLF [P > 0.05]. Also, there was no significant difference in the HRV measurements between overweight and obese groups of the women with preeclampsia as well as the controls. The study revealed that preeclampsia could occur in the absence of obesity.