New Beginnings Doula Training

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Monday, September 19, 2011

How a fetus promotes oxygenation and the fetal heart rate

This is something that I find truly amazing: The ability of the fetus to adjust to various environmental decreases in oxygen.  I'm going to try and show this in an easy to understand way and hopefully it'll make sense.

First off, the two parts of the nervous system work together to keep the heart rate between 110-160.  The parasympathetic nervous system will decrease the heart rate while the sympathetic nervous system increases the fetal heart rate(fhr).

Normal fhr characteristics are due to the interaction between these two.  This includes the normal baseline rate and accelerations from the baseline.  This indicates that the fetus has an intact and well oxygenated brainstem, autonomic nervous system and heart.

Here's an idea of how different receptors and hormones work along with the nervous system.

An increase in blood pressure causes the baroreceptors to respond.  This stimulates the parasympathetic nervous system which then causes the heart rate to drop and then a decrease in blood pressure.

Chemoreceptors respond to changes in oxygen, CO2 or pH levels.  These changes stimulate the parasympathetic nervous system which then leads to a decrease in heart rate and lowered blood pressure.  It may also lead to a increase in heart rate and an increase in blood pressure.

Low oxygen levels or pH level also lead to the release of epinephrine and norepinephrine.  These increase the fhr as well as shunt blood to the most important organs: the brain, the heart, and the adrenal glands.  This also causes an increase in blood pressure.

Low blood pressure and oxygen will also release vasopressin.  This increases your blood volume and constricts your blood vessels which then increase blood pressure.

The kidneys will excrete renin and angiotensis when the blood pressure is low.  This causes the blood vessels to constrict by retaining salt and fluid.

The placenta and umbilical cord even get in on the act.  When a baby has low oxygen levels, they secrete prostacyclins and thromboxane.  This cause the blood vessels of the placenta and umbilical cord to dilate, allowing more blood through and thus more oxygen.

Again, I think this is all pretty amazing.  This little babies are pretty well equipped to deal with labor pretty well.

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Birth is a Journey: Does it have to be life changing?

  • One woman might have to climb on an overfilled boat, risking her life and nearly dying as she escapes over the ocean to come to this land. This experience could certainly be life altering. It may very well color the rest of her life, positively or negatively. (I overcame this amazing struggle and here I am triumphant! OR Holy crap, that was SO hard I don’t know if I can go on! By the way, neither response is “right”. No one would judge the woman with the 2nd response.)
  • One woman may buy an airplane ticket, sit on a comfortable 747 and fly to America with a nice smooth flight and landing. She is happy to be in America. Those welcoming her are glad she is here safe and sound. She may only travel by plane 2-4 times in her life, so it is pretty memorable. But the journey itself probably wouldn’t be life changing; it would simply be a journey.
  • One woman may learn to fly an ultra-light plane to lead a flock of geese into America teaching them to migrate. This experience could certainly be empowering and life altering.