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Stretching the belly and the heart

Updated: May 27, 2021

Pregnancy can be emotional, tiring and infuriating but sometimes it’s forgotten how fascinating and mind-boggling the whole progress is.

With mother not only having to keep themselves healthy but also keep the human being inside them growing.

There are many ways in which the maternal body adapts to pregnancy. The blood is supplied to the foetus from the placenta through the two umbilical arteries into the baby and then returned back to the placenta through the umbilical vein.

The foetus puts extra demand on the circulatory system to provide this rapidly growing life with oxygen and nutrients whilst also taking away the waste products. During pregnancy, there is an increase in the hormone Progesterone. This hormone decreases the vascular resistance leading to a decrease in the diastolic blood pressure (pressure in the blood vessels when the heart is relaxed). The bodies response to this is to increase the cardiac output of the mother heart by 30-50% more than non-pregnant women. This occurs due to an increase in both the heart rate and the stroke volume (the amount of blood being pumped out of the heart with each beat).

During pregnancy the renin-angiotensin system within the kidneys is activated, the role of this is to increase blood pressure. This system when activated causes an increase in sodium and water retention leading to an increased total blood volume. This increased blood volume can cause oedema and 90% of women produce a heart murmur due to this, this is normal.

Due to the increased blood volume and increased cardiac output pregnancy basically acts as an exercise test on the heart. Some women’s hearts might not be able to cope with this extra stress, this is why the cardiac disease is one of the leading causes of maternal death in the UK. During pregnancy, the change of acute myocardial infarction (heart attack) increases by 3-4 times the normal risk. However simple lifestyle factors can be put in place during pregnancy or even whilst planning conception to reduce this risk. These include healthy eating (to reduce cholesterol), exercise to increase the strength of the cardiac muscle and its blood supply and quitting smoking. This is why chest pain in pregnant women is taken very seriously.


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