Why all of a sudden do you feel like it is 3 x harder to walk up a hill or a stairwell, or why has your iron levels dropped?
Blood volume increases significantly within the first few weeks of gestation and increases progressively throughout the pregnancy. The total blood volume increase varies from 20% to 100% above pre-pregnancy levels, usually close to 45% of average woman.
"A healthy woman bearing a normal sized foetus, with an average birth weight of about 3.3 kg, will increase her plasma volume by an average of about 1250 ml, a little under 50% of the average non-pregnant volume for white European women of about 2600 ml. There is little increase during the first trimester, followed by a progressive rise to a maximum at about 34-36 weeks, after which little or no further increase occurs." (National Library of Medicine) A non-pregnant woman has about 100ml of blood per minute flowing through the uterine artery, but in early pregnancy this increases to about 120 ml per minute. Once a woman is close to her due date, the blood flow has increased to about 350 ml per minute.
Interestingly enough the research shows that physically active women possess significantly greater vascular volumes than their sedentary counterparts.
WHY DO WE GET AN INCREASE
Pregnancy requires dramatic changes in blood flow, the most obvious being that which occurs in the uterus and the development of the placenta to make a baby grow.
WHAT OTHER THINGS HAPPEN AS A RESULT OF THIS INCREASE?
- Blood flow to the skin increases, making a newly pregnant woman feel warmer and perhaps sweat more, particularly from her hands and feet.
The increase boosts the body metabolism by about 20%, creating more body heat and making pregnant women less likely to feel the cold the body temperature will often rise to about 37.8 C degrees. (Normally 37)