“Is life worth living? This is a question for an embryo not for a man.” Samuel Butler
It’s early December, and we are well into the flurry of holiday shopping. For some, gift-giving is a studied art. Finding that “perfect gift” for each person on the list seems almost an obsession to these folks. And though giving to many can be a joy, there’s a significant element of stress in these days as we all race toward the finish line of another year. So, I, like many of you, have gift-giving on my mind.
In pondering the elements of a perfect gift, I believe that unique, personalized gifts are the ones I appreciate the most from others. The meaning behind such gifts is that the giver understands me well enough to single me out in their thoughts for a unique ‘one of a kind’ offering. Especially homemade and/or handmade gifts are meaningful expressions of caring; they are tangible reminders of the time and effort that a friend or relative took to create a present just for me. As Ralph Waldo Emerson so aptly stated, “The only gift is a portion of thyself.” In such a mindset, I have pondered the Gift of Life. After this research, I marvel even more that human conception succeeds at all! So, this week, review with me our precarious and precious beginnings, and see why Life is indeed, the greatest gift of all.
A successful conception is a complex orchestration; there are multiple players and timing is everything! Basically, a woman is “fertile” only 6 days each cycle: the 5 days leading up to, and the day of ovulation (when the egg is released from the ovary). As a consequence, the timing of intercourse within this fertile period is also critical. The likelihood of pregnancy decreases from 36% if intercourse occurs two days before and/or on the day of ovulation to 10% if it occurs 4 to 6 days before ovulation. And sperm can only live up to five days themselves. So, even though the decrepit five day old “codgers” can fertilize an egg if they make the journey from vagina to ovum in time, they’re not as likely to succeed.
Let’s drop back and look at individual players and their histories before reconsidering the final performance. Sperm are constantly produced in the testicles of an adult male from puberty throughout the remainder of life. A mature sperm is formed in the testicle in a step wise process over 70 days. It starts as a very basic cell but by the time of its maturity, it contains the male genetic information and is also capable of actively seeking out and fertilizing an egg.
At the moment of ejaculation in intercourse, the sperm are catapulted from testes through the vas deferens, through the urethra and into the vagina. They travel from there into the cervix; the deposited sperm make this journey within a matter of minutes. The journey then proceeds through the cervical mucus, into the uterus, and up into the fallopian tubes. Though millions of sperm are generally deposited in the vagina, only a few hundred survive the journey to the fallopian tube (analogous in distance to a human swimming the English Channel back and forth seven times). Can’t you see why survival of the fittest is absolutely true in this instance? And, the front runners complete this amazing journey in just a few minutes.
The vast majority of sperm deposited in the vagina do not make it to the cervix. The acid balance of the vagina kills them, or they simply “leak out” after intercourse. And, of the entire volume of ejaculate, only the sperm themselves are capable of making it through cervical mucus and on to the rest of the journey.
Okay, so what about the female players in conception? Unlike the ongoing production of sperm that a male has throughout adult life, a woman has all of the eggs she will ever have (usually about two million) when she is born. This supply decreases until menopause when the egg supply is depleted. During each cycle many eggs begin to develop over about two to three weeks, but only one reaches maturity; the rest of ‘this month’s batch’ simply degenerate and are gone forever. The single mature egg is released from the ovary and sits on the surface of the ovary surrounded by protective cells. If not fertilized within 12 to 24 hours at most, this egg too, is simply resorbed by the body and is gone.
This mature egg has to make its way into the fallopian tube. . .and if you’ve always thought that’s an easy process. . .read on. There are finger-like projections from the end of the fallopian tubes (called fimbria) which must actively seek out the egg and pick it up from the surface of the ovary. The egg doesn’t just conveniently drop itself into the tube and head south for a uterine tour. The fimbria move the egg along the surface of the fallopian tube lining cells to a portion of the tube called the ampulla. It’s usually here that the meeting of egg and sperm occur. Interestingly, though only one sperm gets to declare ‘fertilization victory’, many sperm are involved in the preparation process. Because there are many protective cells surrounding the mature egg, multiple sperm are involved in the process of actively removing these cells so that a single sperm can have a clear, unobstructed path to penetrate the egg. And, once this little stud makes it to the ovum, the protective layer around the egg immediately transforms to prevent any further sperm from entering the egg. What an amazing sequence of events! Can you see why our creation is truly a miraculous process?
After fertilization, the early embryo (or zygote) stays in the tube for three or four more days–though development is clearly underway. When it finally makes it to the uterus, the embryo is usually just about 20–40 cells in size. It will ‘float’ in the uterus before attaching to the wall (implanting) a couple of days later. At each step of this fascinating process, you can see how multiple opportunities for failure could occur.
Age, health, and habits of the Mom and Dad all play critical roles. Couples in their early 20s with no fertility problems have up to a 20–25% chance of becoming pregnant each month, but this figure can drop to 1–2% chance per month for a healthy couple in their 40s. Smoking by either parent seems to be a big deterrent to fertility. And, even the Mother’s mental health has a significant contribution. Studies indicate that infertility is twice as common in potential Moms who are depressed. When Moms’ hormone cycles are erratic–affecting such elements as timing of mature eggs, character of cervical mucus, and preparation of the uterine lining–many aspects of potential conception are jeopardized. Conversely, when Dads’ sperm counts are low and/or the little swimmers aren’t particularly rigorous or aggressive, likelihood of successful conception is decreased. And, even when fertilization is successful, 15–20% of all pregnancies end in miscarriage.
I was a little surprised (and amused) to see several time-honored tidbits of fertility wisdom dashed. Multiple recent studies have disproved the notion that moderate coffee consumption decreases women’s fertility. Additionally, there’s no reason for a women to stop her regular exercise routines if she’s having normal, regular menstrual cycles. Finally, my favorite, a 1997 study at Los Angeles Medical Center, found that even men who wore crotch-hugging polyester-lined underwear did not have lower sperm counts than their boxer-wearing buddies. So, guys, keep wearing those briefs if you like ’em! However, studies do show that smoking only 10 cigarettes/day can lower a man’s sperm count by 20%.
So, as you plan and ponder the perfect gifts this season, take a little time to marvel at your own creation, and be thankful for this miraculous gift of life. We beat incredible odds and successfully pass through a litany of steps to survive even one week into our precious lives. Never take yourself for granted; rather celebrate the contribution you make to your job, your family, your environment. You are a unique, ‘handmade’ gift to the world. Remember, “Use what talent you possess: the woods would be very silent if no birds sang except those that sang best.” Henry Van Dyke
Stephen L. Hines, M.D.
December 2000
