During the pregnancy plasma volume increases by 50%, which increases preload. The maximum increase in plasma volume occurs during first two trimesters of gestation. The rise in preload will increase contractility of the heart and stroke volume increases by 30%.
Total peripheral resistance decreases due to the parallel connection of fetus. This will increase the heart rate by about 20%.
The rise in heart rate and stroke volume will cause an increase in cardiac output by approximately 50% (CO = HR * SV). This massive increase in cardiac output will cause systolic ejection murmur along the left sternal border and it is perfectly normal during pregnancy. Do not confuse this murmur with hypertrophic obstructive cardiomyopathy or aortic stenosis.
The inferior vena cavasyndrome is a positional hypotension that occurs due to the compression of inferior vena cava by the uterus when a pregnant woman lies in the supine position. This compression decreases venous return and also decreases cardiac output. Management of this syndrome is to ask a pregnant woman to lie on her left lateral position. However, diastolic murmurs are never normal, and they must be investigated further.
Central venous pressure is unchanged in pregnancy but femoral venous pressure increases by 2-3 times by the end of 2nd trimester. This increase in femoral venous pressure will cause varicose veins or hemorrhoids (very common) in a pregnant woman. This pathology resolves after the delivery.
Typically, blood pressure decreases during pregnancy by 10-20 mmHg. It is never elevated physiologically in pregnancy. Both systolic and diastolic blood pressure starts falling by the end of the first trimester of pregnancy. Lowest blood pressure in the pregnancy is at around 24th week. After 24 weeks, blood pressure increases again till delivery. Even though blood pressure increases, it does not go above the pre-pregnancy measurements. Gestational hypertension, pre-eclampsia, and eclampsia are three conditions where blood pressure pathologically increases to very high level. Eclampsia is defined as preeclampsia + seizures.
Other things that are considered normal for a pregnant woman is an increase in ESR, clotting factors (increased risk of deep venous thrombosis), WBC count, RBC mass and decrease in hematocrit (dilutional effect due to high plasma volume).
Adapted from: Fundamentals of Cardiology: Concise Review for USMLE and General Medical Boards To review any cardiac condition, just search on google followed by 'medrx education'. For example: Atrial fibrillation medrx education. You can also review all up-to-date materials in our book "Fundamentals of Cardiology".