The presence of sinus rhythm on the EKG of a pregnant woman is a normal physiologic condition and nothing to worry about. Sinus rhythm is a normal ECG manifestation, whether it is a pregnant woman or someone else. The normal human heart has a rhythm, and this rhythm is issued from the sinus node, and then through the conduction system of the heart, downward transmission. Normally it is initiated from the sinus node, so it is called sinus rhythm. If the initiating rhythm is irregular, sinus arrhythmia occurs. If it is initiated from a site other than the sinus node, it is called an ectopic rhythm. These are abnormal conditions. Pregnant women who experience panic attacks, chest tightness, etc., and who also have abnormal EKGs when examined need further cardiac ultrasound to clarify the cause.