The Womb—Our Marvelous First Home
WHAT a marvelous place, your first home! Warm and cozy. Well stocked with rich nourishment. Safe and secure.
You spent months there, thriving and growing. Soon, though, your quarters seemed to be getting tighter and tighter, till one day you could barely move. Likely, by that time you were even standing on your head! Then, all at once, you felt yourself being squeezed by powerful forces, and you burst through the door of your home into the cold, noisy, brightness of the outside world.
You don’t recall any such experience? No doubt you do not. But you owe your life to that wonderful place in which you were housed—your mother’s womb. It was perfectly designed with you in mind, providing all the nurturing and protection a developing baby needs. So why not journey back and take a tour of that marvelous first home of yours—the womb?
A Warm Welcome Awaits You
Your life probably began while en route to this fine home. A ripe ovum from your mother traveled down a tunnel called the Fallopian tube. Meanwhile, millions of sperm cells from your father were on their way up the same road to meet this egg head-on. One sperm succeeded in fertilizing the egg, and thus you came to be you.
By this time preparations for your arrival were already under way. The walls of the womb, or uterus (Latin uter, for “bag”), had been preparing themselves, and the place was fairly brimming with nutrients. The lining of the uterus had swelled to twice its normal thickness, with a soft spongy coating.
After three or four days, you passed over the threshold of your new home. To you—a pinhead-sized cluster of a few dozen cells called a blastocyst—it might have seemed like a sprawling cavern. Inside, however, the space is quite small. Actually, the uterus is a hollow organ, smooth and pinkish, about the size and shape of an upside-down pear.
This would be your home for the next 270 days or so, and your mother, even at the expense of her own body, would provide you with the nutrients you need to grow and develop till it was time for birth. Several weeks would pass before your mother even realized you existed, and it would be another three to four months before her belly would protrude enough for others to notice.
After a free fall into the uterine cavity, you floated around for three more days. Finally, you attached yourself to the uterine wall. Enzymes from the blastocyst digested the surface cells of this plush lining, called the endometrium, and you sank down and nestled securely in the velvety depths. Had an egg not been fertilized and implanted in this lining, the uterus would eventually have shed it and expelled it from your mother as the menstrual flow.
Coping With Rejection
Marvelous processes were now at work to ensure that your stay was a pleasant one. For one thing, you needed protection from your mother’s own immune system. Scientists are still puzzled about why your mother’s body didn’t consider you a foreign intruder and attack you. Normally, the complex rejection system springs into action at the first sign of any invader. Yet, you would eventually grow to be a foreign body of gigantic proportions, weighing several pounds. Why did you not come under siege?
Researcher David Billington of the University of Bristol explained: ‘Essentially you’ve got a wall between the mother and the fetus. The wall fairly effectively stops any traffic between the mother and the fetus.’ He was referring to a layer of tissue called the trophoblast, which surrounds the fetus. This barrier prevented any direct contact between you and your mother. Just why her immune defenses didn’t challenge the trophoblast as foreign tissue is a mystery. The answer to this question might also tell us why some pregnancies end in miscarriage.—See box on page 16.
Nourishing and Nurturing Continue
Consider your insatiable appetite for nourishment, especially during these early stages. In your first eight weeks of life, you increased in length about 240 times, and your weight grew to a million times more than at conception. Ultimately, your birthweight would be some 2.4 billion times that, with your amazing home expanding like a balloon to accommodate you. The womb then weighs about 16 times the nonpregnant womb, but within a few weeks after delivery, it shrinks back to nearly original size. The first trimester of life saw the basic structure of your body form, with organs and nervous system ready for the stages of development to follow.
Early on, the watery amniotic sac formed. It provided you with a cushioned, temperature-controlled playroom in which to tumble and frolic in your second trimester. You were strengthening muscles you would need outside the weightlessness of the bag of waters. You swallowed amniotic fluids by the mouthful, presumably for nourishment. Every two to three hours, the fluid was replaced for you.
From the outer wall of the blastocyst grew an intricate pad of tissue called the placenta (Latin for “flat cake”). Consider some of the services it performed for you.
It acted as a lung, exchanging oxygen and carbon dioxide between you and your mother. Acting as a liver, it processed some of your mother’s blood cells to extract necessary components, such as iron, for your use. Its function as a kidney filtered out urea from your blood and passed it to your mother’s bloodstream for excretion through her kidneys. Like the intestines, the placenta digested food molecules. All these processes took place through the 22-inch-long [55 cm] umbilical cord.
It was once thought that the placenta was an impregnable security system, that it would allow nothing harmful to pass from mother to child. Sadly, we now know that many infections can breach the security system, as can substances like the infamous drug thalidomide. Diseases such as German measles also pose a threat in certain stages of pregnancy.
The blood-brain barrier present in adults is not yet well established in the developing fetal brain, leaving it especially vulnerable to such invaders as cigarette smoke, alcohol, drugs, and other chemical toxins. Research shows that alcohol does create adverse effects in an unborn baby. Does caffeine, which crosses the placenta, influence the infant’s development? Do vitamin supplements benefit the developing child in any way? More needs to be learned about such questions.
The protective system for any baby, therefore, must begin with its mother’s own care to avoid taking in any substances known to be harmful to infants. On the positive side, a balanced diet and exercise, upon doctor’s approval, may go a long way toward promoting the general health and well-being of mother and child.
Bidding Your Home Farewell
Deep into the third trimester, preparations began for your departure. The strong muscles of the uterine wall began an irregular contract-and-release exercise sometimes called false labor. The uterus became softer and more elastic.
Instead of saying, “The baby dropped,” it is more accurate to say that the entire uterus dropped, with the baby inside. This is so because it straightens into a cylinder and lowers a bit so that the baby’s head is now in the pelvic bowl.
No one knows what decided that it was time for you to move out. It might have been hormones from your mother, or from you, the baby, that signaled the womb. The message: “Begin labor!”
“Labor” well describes the three-stage process that the uterus initiated. First, the muscular walls of the uterus contracted while the cervix and vagina dilated in preparation for your descent. The bag of waters probably broke at this point.
Second, mother’s work really began as she pushed her baby’s head downward through the cervix and the vagina. The contractions continued, coming stronger and faster until your head finally passed through the birth canal. The rest of you followed easily. In the final stage of labor, your mother expelled the placenta and the remains of the umbilical cord, the afterbirth.
So there you were—startled, cold, and crying—no doubt lamenting your sudden departure from your hospitable home of the last nine months or so. But how glad you can be that you have the gift of life and can appreciate the care of a loving Creator, who saw to it that you had a fine home right from the start!
[Box on page 16]
Miscarriage—The Tragic Eviction
TRAGEDY may strike even the most caring mother. The causes of miscarriage are elusive and the debates heated. Researchers don’t even agree on the percentage of successfully fertilized eggs that end in spontaneous abortion. Estimates range from 10 percent to 20 percent or even more of pregnancies in the general population of women in the United States.
Why does the womb sometimes forcibly evict its new life instead of cradling it protectively within? Possibly the mother’s immune system responds defensively to the surrounding trophoblast, attacking its protective wall and causing miscarriage. Many may be caused by so-called genetic accidents, the embryo or the fetus being so damaged that it cannot live. Or it could be abnormalities in the reproductive process—an egg’s prematurely entering the uterus before the lining is ready to receive it or so late that the endometrium is already beginning to shed. Perhaps some deformity in the mother’s uterus itself makes her unable to carry a child.
A study of nearly 200 women in Britain (1990) suggested that infertility and miscarriage may be linked to hormonal imbalances. Output of LH (luteinizing hormone), originating in the pituitary gland, usually rises on about the 14th day of the menstrual cycle and causes a ripe ovum to burst through the ovary and begin its journey down the Fallopian tube for possible fertilization. “What the British team found,” reported The New York Times, “were large amounts of LH at an inappropriate time, on the eighth day of the menstrual cycle, before ovulation.” More testing is needed to confirm and interpret these findings.
[Pictures on page 15]