Re: Dobabies get air in the mothers stomach and if so how?

Hello, Bronte, and thanks for asking your question.

A fetus (what we call a baby before it's born) receives oxygen through the 
umbilical cord, just as the baby receives nutrition that way.  We all 
breathe to obtain oxygen after we're born, and we use our blood to 
transport that oxygen from our blood to all of the tissues of our body, 
such as muscle, bone and organs.   The red pigment in our blood (called 
heme) is part of a special protein (called hemoglobin) designed to carry 
the oxygen from our lungs to the tissues where it's needed.  It doesn't 
carry the oxygen as bubbles of oxygen, but rather as individual molecules 
of oxygen.  

When a woman is pregnant, the fetus within is connected by an umbilical 
cord to an organ on the wall of the womb called a placenta.  The placenta 
handles the job of the interface between the fetus's blood supply and the 
mother's blood supply.  Within the placenta, the blood supplies of the 
fetus and mother almost come in contact, with only a thin membrane 
separating the two blood supplies.  

Because the fetus's blood (specifically, the fetus's hemoglobin) has a 
higher affinity for oxygen (meaning it is better than mother's blood 
at "soaking up" oxygen), the oxygen transfers over from mother's blood to 
the fetus's blood across that membrane.  Nutrition and carbon dioxide make 
it across the membrane by different processes than the one I've described 
here.  

When the fetus is born, the placenta detaches from the womb and is 
delivered after the baby.  This cuts off the oxygen supply from the 
mother.  Before that happens, though, the baby takes it's first breath, 
using its lungs to start bringing in oxygen in the way with which you're 
most familiar -- breathing.  After that, the baby is dependent on its 
lungs for obtaining oxygen, unless they are at some time hooked up to a 
heart-lung machine, which can mimic the ways the lungs obtain oxygen for a 
short time.

After the fetus is born, it stops making the special fetal hemoglobin and 
switches to making the same hemoglobin that the rest of us make (as long 
as it doesn't have a hemoglobin protein problem, like in certain blood 
disorders such as sickle cell disease and thalassemia). 

I hope that answers your question.  Stay curious!

Tim Nicholls, MD
Berkeley, CA