I AM A PINKISH muscular pouch, suspended by ligaments in the lower abdomen. Roughly the shape of a small pear, I weigh about two ounces. I suppose I could be best described as a brood chamber, but that scarcely does me justice. For I can perform what may well be the supreme wonder of the universe: I nursemaid a barely visible cluster of a few cells until it becomes a complex of trillions of cells - a new human being. I am your womb.
The job of providing a nursery for a new life would appear to be simple enough. Actually, it is awesomely complex - and quite frustrating for me. Each month from puberty to menopause I go through the elaborate ritual of preparing for pregnancy. This has happened - or will happen - upward of 400 times. It is something like preparing elaborate banquets for guests who rarely arrive - 400 invitations, only a few acceptances!
These monthly preparations involve dazzling chemistry: construction of an intricate network of new blood vessels, new glands, new tissues. Under the prodding of the estrogen hormones from your ovaries, my lining - the blood red, velvet-smooth endometrium - thickens and my glands enlarge to provide essential nourishment for a new life. At mid-cycle, another chemical event of utmost importance occurs.
Remember, I am a hollow, muscular organ, my interior space would hold about a teaspoonful of liquid. My muscles contract regularly. But these contractions would be deadly to a fertilized egg. To relax my muscles, your ovaries at mid-cycle start producing the hormone progesterone. The progesterone performs two really important functions. It helps prepare my lining for implantation, and it causes my gland (which have already been stimulated by the estrogen) to start secreting nutritional substance necessary for the nourishment of the fertilized egg in its early stages of growth.
I have three openings. Two fallopian tubes feed into my upper portion to deliver the single egg released each month by one of your ovaries. My third opening is the straw-size tunnel through my cervix, or neck. This is my entrance for male sperm, and my exit for a baby. At the time your ovary is releasing its egg, my cervix steps up production of its mucous glands - to provide a stream through which the male sperm can swim toward the egg.
I am now prepared to receive the fertilized egg, and proceed with nurturing a new life. But when no fertilized ovum is delivered, all of the new tissues, glands and blood vessels I have provided must be discarded. Order is restored when you have your period.
My big moment came/comes with your first baby, when I finally got an opportunity to show my virtuosity. The egg had been fertilized, and cell division was already under way. The increasing cells had but one food supply during the leisurely trip down the fallopian tube - the egg's yolk - and that was about gone by the time the egg reached me. Unless a dependable source of nourishment could be promptly found, survival prospects for this minute fleck of life looked dim indeed. Yet, as I had been so many times before, I was ready. With death just about at hand, the egg shot out tiny feelers for attachment to my endometnum. It now had a safe, warm, food-supplying home.
To feed my demanding new guest - a task that would continue for nine months, 24 hours a day - I would be helped by one of the most miraculous and complex of all tissues, my placenta. Minute at first, it sprouted as a fleck from the fertilized ovum and eventually grew into a reddish two-pound pancake, about seven inches in diameter. No beauty, it would function as lungs, liver, kidneys and digestive tract for your baby until its birth.
The baby's lifeline was its umbilical cord, which may be as short as five inches or as long as four feet. The cord contained two arteries and one vein; the arteries carried wastes from the baby to the placenta, where they diffused into your bloodstream. The wastes were then disposed of by your liver, kidneys and lungs. The vein brought nourishment from your blood - vitamins, oxygen, minerals, carbohydrates, amino acids. The placenta's gossamer-membrane filtration system handled these intricate exchanges even as it kept your blood and your baby's completely separate. They were of incompatible types, and to have allowed them to mix would have brought on disaster.
As your baby grew - at the end of the first month my tenant was 10,000 times the size of the fertilized egg - my capacity was increasing until eventually it would be 500 times its original size. My shape, too, was changing - from pear to globe to ovoid. Perhaps most important, I was growing enormously stronger. My muscle fibers increased dramatically in size and weight. But for this growth, I might well have burst with the increasing size of my tenant, particularly after it learned to flail and kick. I would need this added strength when it came time for the sustained labor of birth - exertion that would exhaust a superman.
Until about the seventh month the baby changes position frequently, but then gravity takes over. The head now disproportionately heavy; so, like 96 percent of all babies, it assumes a head-down position by far the best for birth. As my boarder increased in size and strength, I simply pushed aside anything that got in my way. I brought pressure on the bladder, necessitating frequent trips to the bathroom. There were digestive upsets also, resulting from all the shoving I did on the stomach and intestines.