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Maternal Changes

by Thad Wilson, PhD
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    By having this large amount of blood going to the placenta, what does this do to overall cardiovascular control for the mom? Well, if you would plot out the weeks of gestation versus the percent change in a particular variable, systemic vascular resistance plummets. In fact, over the first about 15 weeks, it is almost a linear drop as those spiral arteries have now engorged and it become wider you have little ability to resist flow. As systemic vascular resistance decreases, what has to happen? You have to have an increase in cardiac output. So the mother's heart is tasked more because of this vascular bed that is new to the system and is open wide and doesn't constrict. Therefore, you have increases in heart rate and stroke volume so this is almost like a sympathetic stimulatory stress most of the time during those first number of weeks of gestation. Interesting though, her mean arterial pressure stays fairly constant. So that decrease in systemic vascular resistance which she cannot control is accommodated by the increase in cardiac output. Now what changes happen in the cardiovascular system besides those of cardiac output and systemic vascular resistance? The big one is is there is a change in blood volume. So the renin-angiotensin-aldosterone system is engaged to a great extent and you retain fluid and as you bring in fluid to the body as you're drinking and so forth, you're not urinating out as much fluid. So you start to really retain fluids. This has an interesting effect on some of the blood components and the most interesting one is it's effect on hematocrit. You will get a decrease in percent hematocrit as gestation moves along to about week 30 and then it flattens out. What does a decrease in hematocrit mean? Did...

    About the Lecture

    The lecture Maternal Changes by Thad Wilson, PhD is from the course Reproductive Physiology.


    Included Quiz Questions

    1. Plasma volume
    2. Hematocrit
    3. Systemic vascular resistance
    4. Placental vascular resistance

    Author of lecture Maternal Changes

     Thad Wilson, PhD

    Thad Wilson, PhD


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