WHY CHILDBIRTH IS SO MYSTERIOUS
The nine-month wait is finally over, and
the baby so longed for is about to be born. The expectant mother’s cervix has
remained firmly shut, keeping the fetus safely in the womb. But now her cervix
thins, softens, and relaxes. The miracle of birth begins.
What is behind the marvelous process of
childbirth? Of the several factors involved, two are especially amazing. First,
OXYTOCIN, a hormone
produced in the brain, is released. Both men and women produce this substance,
but a great quantity of it is released in the pregnant mother when labor
begins, causing the cervix to dilate and the uterus to contract.
Just how the pituitary gland of the expectant
mother knows when to begin releasing this hormones is a mystery. The book
incredible Voyage- Exploring the Human Body states: somehow her brain senses
that gestation is complete and that it is time for the powerful uterine muscles
… to take on their brief but heroic job.
A second factor involved in this process is
the role of the placenta,
which stops producing progesterone. During pregnancy, progesterone has
prevented strong contractions. But now, without the restriction of
progesterone, the uterus begins to contract. Generally after between 8 and 13
hours of labor, the baby is pushed out through the relaxed, dilated cervix.
Afterward, the placenta is also expelled.
Now the newborn must quickly
adapt to new conditions of life, very different from those of its maternal
environment. For example, while in the uterus, the lungs of the fetus were full
of amniotic fluid, which was squeezed out when the infant passed through the
birth canal. Now the lungs must be filled with air to initiate breathing, the
onset of which is usually indicated by the first cry. Drastic changes also
occur in the heart and the rest of the circulatory system. A hole connecting
the two atria of the heart and a blood vessel bypassing the pulmonary
circulation close, in order to reroute the blood through the lungs, thus
enabling the blood to absorb oxygen. It is astonishing that this adaptation to
the outside world happens so rapidly.
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