Cardiovascular changes

The heart

Increases in size as it pumps blood through the placenta, fetus, and the much larger uterus and abdomen.

The heart beats 15 beats per minute higher and the stroke volume is about 7ml larger per heart beat.

Blood volume 

The higher circulating blood volume-increased by 30-50% during pregnancy- is necessary to provide extra blood flow through the placenta, so nutrients and oxygen can be delivered to the fetus. 

Blood pressure 

As the muscular walls of the blood vessels relax slightly, the blood is circulating in slightly wider blood vessels and the blood pressure is reduced.

Exercise and blood flow

Steady, non-violent exercise is good for the mother because it prepares her body for labour.

Sudden, strong exercise, or working for too many hours may make her feel dizzy.

She should not exercise lying on her back as the weight of the uterus will press on the major blood vessels returning blood to her heart, and she will feel dizzy.


Oedema is the swelling of tissue caused by the build up of fluid in the body. The swelling can occur in the legs, feet, and hands after the first trimester.

Last modified: Wednesday, 8 October 2014, 11:50 AM