Plasma volume increases by 40-50% as pregnancy progresses. The elevated diaphragm and increased blood volume displace the apical impulse upward and laterally. Innocent midsystolic murmurs are common, best heard at the upper left sternal border. Splitting of the second heart sound is normal. Occasionally, a systolic-diastolic bruit is audible over the breast or over the gravid uterus, signifying flow through a functional arteriovenous shunt. Blood pressure (especially diastolic) tends to fall in early pregnancy and rise to prepregnancy levels toward term.