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INTRODUCTION
Please note: This page is very graphic intensive.
It is now two weeks from your last menstrual period. Conception may occur today! Well, at least in the previous few or next few days, depending on the length of your cycle. The egg and sperm will meet, creating a single cell organism called a zygote will start to divide. You may want to start preparing for the psychological part of pregnancy now. Around now, if the egg was fertilized, it will drop into your uterus. Now that the fertilized egg (or zygote) is in your uterus, fluid will enter dividing it into two. One will be the placenta, the other will be the baby.
OVULATION OCCURS!
The ovum cell enters the fallopian tube after ovulation. The fallopian tube's finger-like projections, called the fimbriae, have captured the ovum cell, which is surrounded by thousands of nutrient cells. The forest of cilia propel it forward towards the uterus.
Slight bleeding may accompany ovulation, and if the blood is shed against the perineum (the membrane surrounding the abdominal cavity) there may be discomfort (called mittelschmerz). This makes it easier for the woman to calculate the most propitious time for conception.
Once inside the fallopian tube, the ovum is contained in an environment that suits it just as well as when it was inside the follicle. It now ripens increasingly, preparing itself for the encounter with the sperm. Rather than remaining immobile, it rolls slowly over the surface of the membrane folds while awaiting its male counterpart, the sperm cell. Half of the chromosomes in the ovum, expelled when it ripens, collect in a cell called a polar body inside the ovum wall (see right photo).
Meanwhile the emptied follicle is transformed. The hormone-producing cells that did not escape from the follicle during ovulation start growing and change their hormone production. Until now, the predominant hormone formed in the follicle was estrogen. This production now declines sharply and the corpus luteum starts producing progesterone instead.
A change in the information sent to the ovary by the brain and pituitary gland can result in more than one ovum being released at the time of ovulation; either one ovum from each of the ovaries or two (or more) from the same ovary. Twins or triplets may be conceived. If this happens, the result is always non-identical (fraternal or dizygotic) twins, which may even be of different sexes. They are no more alike than any other two siblings. Identical (monozygotic) twins, on the other hand, result from the fertilization of a single egg cell that then divides into two equal parts; thus, the fetuses are of the same sex and genetically identical.
FERTILIZATION
Fertilization, the moment the sperm and egg fuse and a new individual begins to form, has been until recently shrouded in mystery. Once drawn into the funnel of the fallopian tube, the ovum comes to rest in the outer, broad portion of the tube. Surrounded by a sticky sheath of nutrient cells, the tiny ovum cell can barely be discerned.
Sperm may already be in the fallopian tube, or they may arrive later. The ovum, however, is capable of being fertilized for only some 24 hours. If no sperm arrive, it gradually degenerates and travels down through the fallopian tube and uterus into the vagina. The woman then has her menstrual period two weeks later.
During intercourse, sperm are ejaculated against the opening of the cervix at the far end of the vagina. Conditions in the vagina activate the sperm for about half an hour before they start moving up toward the uterus. The initial danger to the sperm is the acidic conditions of the vagina. Once withstood, the sperm then must make their narrow way through of the narrow passages in the cervical mucus. Only the fittest succeed. The journey of 15 -18 cm (about 6 to 7 inches) from vagina to Fallopian tube generally takes several hours. some sperm are high-speed swimmers that, in favorable conditions, can reach the fallopian tube in half an hour. Other sperm take numerous rests on the way, adhering in folds and recesses, but coming unstuck and struggling onward. Their journey may take many hours to even days. During the journey the sperm themselves change. They are affected by substances in the cervix, uterus, and Fallopian tubes, becoming what is termed "capacitated," i.e. capable of fertilizing the ovum.
If there is no ovum in the Fallopian tube, the sperm swim back and forth in the broad portion of the tube, waiting, sometimes for several days. Some sperm emerge through the funnel and swim around in the abdominal cavity among the intestines and other organs. When ovulation occurs and the ovum enters the Fallopian tube, it exerts no particular force of chemical attraction on the sperm. Under a microscope, one can see how sperm quite simply swim past the ovum, at a distance of only a millimeter or so, going straight on until they encounter an obstacle.
The long survival time of the sperm, especially in the recesses of the cervix, means that the intercourse 4 or 5 days before ovulation can result in fertilization. But conception is more likely if intercourse coincides with ovulation. The mucus of the cervix and uterus is then runny and transparent, permitting the sperm to swim upward to the ovum with ease.
TWO HOURS - FIRST ENCOUNTER: The ovum is surrounded by the corona radiata - the luminous halo of nutrient cells. The eager sperm cells cluster against it. This is the first encounter between the ovum and hundred of sperm cells that have succeeded in breaking through all the barriers. A mere hundred survivors out of an original 500 million. They are drilling their heads through the ovum wall, beating with their tails and causing the ovum to rotate slowly counterclockwise.
When the sperm reach the ovum, it is still covered by the sheath of nutrient cells. Some of these cells have performed their function and have been discarded during the passage through the Fallopian tube, but too many still remain for the sperm to penetrate the ovum. They must be cleared away. The cap of the sperm, the acrosome, gradually disappears and enzymes are released. Like a well coordinated venture, the enzymes help the sperm to disrobe the egg. Many sperm perish, others, which never attain full fertilization capacity, still join in the teamwork. After a few hours, at least some of the outer layers have been removed and the surface of the ovum is becoming exposed. Like a bird's egg, the human ovum has a kind of shell but one that is tough and elastic. This obstacle, too, can be overcome by vigorous sperm.
At the moment when a small number of sperm are on their way through the ovum wall, suddenly a single one breaks all the way through, penetrating the inner cell plasma of the ovum. Just then, something remarkable happens. The chemical composition of the ovum wall quickly changes, shutting out other sperm even if they have pierced it. This makes it impossible for additional sperm to fertilize the ovum. If this should happen, further development would sooner or later be arrested since more than one set of chromosomes would be disaster for the ovum and miscarriage would occur. Once the sperm has penetrated the ovum shell, its energetic tail has served its purpose and separates from the head.
The excluded sperm continue to jostle around the ovum with undiminished strength and mobility for several days. Perhaps they serve no purpose; but they may help to promote the distinctive chemical environment that is so important to the ovum and their tail movements continue to make the ovum rotate counterclockwise. The excluded sperm may play a significant part in causing the ovum to start rolling along the mucous membrane surface aiding its passage through the Fallopian tube on its way to the uterus.
The contents of the sperm head contains tightly packed genetic material from the father. When the ovum is fertilized, the tightly packed genes spread out. The pattern looks chaotic, but there is in fact complete order. The molecules consist of DNA and proteins forming a rope-ladder. The sperm's DNA spiral is the man's contribution to the heredity blueprint of the baby-to-be. It contains the X chromosome that determines the baby will be female, or the Y chromosome that will make it a boy. Other characteristics stored in coded form are height, color of skin, eyes, and hair, and other characteristics such as whether the hair will be straight or curly and distinctive facial features, plus much, much more.
THE NEXT 20 HOURS
The moment of fusion is at hand. The head of the sperm with its genetic material, has penetrated the ovum's cell plasma and is steadily approaching the woman's genetic material, which is stored in a nucleus deep inside the ovum. Both nuclei are drawn inexorably toward each other, and soon fuse.
Inside these nuclei, there are round structures in which copying of the DNA message takes place. Some repairs of genes damaged in transport are also carried out. The inner substance of the cell moves vigorously, as if to force together the genetic material that is to make up the new individual. At first, the nuclei are located far apart, with the head of the sperm on the periphery and the ovum nucleus in the center
But slowly they approach each other and fuse. Instantaneously, numerous hereditary characteristics of the new individual are determined. The outer walls of the nuclei then dissolve, and everything is swallowed up by the cell plasma of the ovum.
Roughly 12 hours after the fusion of the chromosomes, the first cell division takes place, and divisions then continue at intervals of 12 to 15 hours. At this stage there are no chemical substances or other mechanisms yet signaling to the woman about developments inside her body.
30 HOURS
A few hours after the nuclei have fused, the fertilized ovum divides for the first time, with a powerful force. It now has two cells, each containing genes from both the mother and the father. Moving slowly toward the uterus, propelled forward by millions of cilia in the Fallopian tub, the cells divide again every 12 to 15 hours. The Fallopian tube harbors risks for the growing cells. They may for example, adhere in one of the many folds of the mucous membrane. If they grow there, the result will be a tubal, also called, ectopic pregnancy.
2 DAYS
The cell divisions continue: four visible cells and 16 cells on their way through the Fallopian tube's thicket of cilia to the uterus. The clump of cells is embedded in nutrient cells that nourish it.
The following pictures show the morula stage (meaning mulberry) and the blastocyst stage, now comprising of about a hundred cells. It is passing through the narrow portion of the Fallopian tube just before entering the uterus. It is a tight squeeze and the blastocyst must push itself forward between the folds.
It takes about three days after fertilization for the ovum to travel through the Fallopian tube toward the uterus. The fertilized ovum normally has no direct contact with the mucous membrane of the tube, but substances flow through the membrane toward the tiny clump of cells that create a favorable habitat. Millions of cilia keep beating in the same direction driving the ovum along. The Fallopian tube periodically contracts and gives the ovum a gentle push.
In the transition between the wider and narrower parts of the tube, there is a barrier in the form of a sphincter muscle which is impassible to the fertilized ovum despite its small size. However, this muscle now suddenly relaxes and the passage leading to the uterus opens. This is primarily due to the secretion of progesterone being produced copiously by the corpus luteum, formed from what was previously the ovarian follicle. The passage through the narrowest part usually takes a few hours with the ovum forcing and jostling its way through the membrane folds without getting stuck.
Once inside the uterus, one of the most critical phases of early development is over. Now the fertilized ovum, in its blastocyst stage, faces new tasks. It has to attach itself to the uterine lining and to signal its presence to the mother. There is plenty of room in the uterus. Soon the blastocyst will "hatch" and rupture its transparent wall.
ADVICE FOR THE MOM
If you haven't already found a midwife or health care provider, you should begin looking now. You need to make choices about who and where you want to have your baby. Homebirth, Birth Center or Hospital? Midwife, Nurse-Midwife, Family Practitioner or Obstetrician? The provider you choose and the place you decide to have your baby will largely determine what type of birth experience you will have and your chances of having various procedures and tests performed and the costs involved. The midwife, as a rule is the least interventive with the lowest cesarean rates and usually delivers babies in homes of the birth moms for less money, while the most interventive tends to be the obstetrician with the highest middle, Nurse-midwives may be found in birthing centers and hospitals. Family Practitioners usually in hospitals, but tend to be less tech-minded then their obstetric counterparts. You will need to decide if you want natural, unmedicated birth (more likely in a homebirth or birth center setting) or a medicated birth (usually a hospital setting). Your basic health status will also determine who you may have. For low risk healthy moms, homebirth or birthing center may be a good choice. For a high risk pregnancy with potential for complications, then a hospital birth is most likely.
Do lots of research and talk to several types of practitioners before you decide. Follow your own instincts and find someone you mesh with. Make sure you feel a sense of trust and comfort with your midwife or health care provider, to have an informative and healthy pregnancy.
A blood pregnancy test may show positive within a few days to 10 days after ovulation. A urine test is usually accurate about a week to 10 days after ovulation.
MoonDragon's Nutritional Guidelines Index
ARTICLES TO READ
SIGNS & SYMPTOMS
Ovulation
Reading Signs of Ovulation
Fertility Basics
Mucus Observation
Ways To Tell When You Conceived
Calculating Your Due Date
Hand Held Calculator
Online Calculator
Pregnancy Calculator
First Signs of Pregnancy
Pregnancy Test - When?
Common Pregnancy Symptoms
Morning Sickness
Implantation Signs
Bowel Tips
Ectopic
Gestational Diabetes
HEALTH & FITNESS
Prenatal Vitamins
Nutrition During Pregnancy
Folic Acid During Pregnancy
Pre-Pregnancy Exercise
Pre-Pregnancy Checklist
Fatigue In Pregnancy
Getting Ready For Another Baby
Things To Avoid During Pregnancy
Pregnancy Don'ts
Miscarriage
Habitual Miscarriage
Dentistry During Pregnancy
Prenatal Exercise
Kegel Exercises
Smoking During Pregnancy
Drugs During Pregnancy
Birth Defects
INSPIRATION & FUN
What Is A Midwife?
Living With A Pregnant Person
When Baby Makes Three
Male Bonding by Kellie Head
Pregnant Fathers Guide to The First Trimester
Things I Wish I knew Before Parenthood
Birthing Within
MoonDragon's Pregnancy Calendar Index
Photos obtained from A Child Is Born by Lennart Nilsson
and Pregnancy - in anatomical illustrations by the Carnation Company
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MoonDragon's Conception Information
Using The Conception Kit™ Instructions
& Ordering Information
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