The Process of Conception
Just one single sperm will make it to the waiting egg. This is a very lucky sperm, being one out of over 200,000,000 to make it all the way. Not only was he one out of 200,000,000 this time around, but one out of several trillion if you consider that you’ve probably been trying to conceive many times. These are big odds.
The intense desire to have children and conceive has been written and sung about for thousands of years. Much folklore and legend has arisen through this inbuilt desire for men and women to continue their line. In some societies and religions, children are thought to have come from reincarnated ancestors out of the spirit realm. In other cultures people believe that the arrival of a baby and especially its conception is reliant on the cycles of the Moon and other natural phenomena.
A lot of women think that conception can only happen when the time is exactly right and they do a host of things to ensure that during ovulation their chances of becoming pregnant are maximised. For other women, conception, pregnancy, and birth are seen as fate and nothing they could do could change the fact that the baby was destined to arrive.
It is actually true to say that for conception to take place, the environment must be optimal. First of all the egg must be in exactly the right place and the sperm must be fit, healthy and ready for action. Actual conception takes place anywhere from 2 to 36 hours following lovemaking. For a baby to develop from this fertilised egg into a fully grown infant, the environment inside the mother has continue to be near perfect too.
The menstrual cycle and how it affects conception
A woman’s monthly period take place over approximately 26-28 days and are referred to as menstrual, (from ‘mene’ – a Latin derivative referring to the Moon). The right moment for fertilisation, approximately once every 28 days, is only possible because the body continually prepares the womb and the egg for that moment.
For many women this is as regular as clockwork. But for many others it is not so predictable. The ovaries and pituitary gland producewhich regulate the monthly periods but the cycle is also affected by overall health and psychological stability. Any type of detrimental influence on either body and mind can throw it out of sync. Things such as bad diet, sickness, and anxiety, even highs and lows – can negatively influence nature’s otherwise regular plan for your body.
A lot of women, desperate to conceive, are actually working against themselves in other areas of their lives. They try to create perfect conditions and get the timing exactly right for conception, but may be neglecting their basic health and fitness levels. Nature has its own regulatory mechanisms. Survival of the fittest ensures that the fit go on to breed and this applies to human beings even in this modern age. So if you are trying to conceive, but are overweight, a smoker, drink too much, or in a stressful job which sends your hormones haywire, you may find it nigh on impossible to fall pregnant.
How the Egg is Prepared for Fertilisation
The human egg is not an inanimate, dead object, waiting for a sperm to breathe life into it. It is a living cell and prior to conception does all it can to increase the odds that it will become fertilised. During the first 14 days following the onset of menstruation, a follicle stimulating hormone FSH, along with luteinising hormone LH, are produced by the pituitary gland located in the brain. These two hormones cause the eggs to ripen within the ovary.
Anywhere from 10 to 15 eggs start to ripen inside the follicles and these follicles start producing ever increasing quantities of oestrogen. It is oestrogen that encourages the release of a lubricating fluid within the cervix that assists the sperm on its travels towards the egg. Oestrogen also plays a vital role to keep the whole process of conception and pregnancy rolling along by its catalyst like affect, as it further increases the production of LH and FSH.
Near perfect conditions for ovulation occur about halfway through the monthly cycle, when a single egg, (or sometimes several), travels up and pierces through its follicle. It then proceeds into the fallopian tube. The rest of the follicles slowly fade away. To give you an idea of how tiny a sperm is, the human egg, which is less than the size of a pinhead, is still 100 times larger than its male counterpart in the conception process.
The human egg like the eggs of other creatures, contains food for the developing embryo. It also contains food for itself as it travels alone toward the uterus along the fallopian tube.
The ruptured follicle draws cholesterol out of the blood after the egg has departed, and it turns a yellow colour, explaining the term given to it – ‘corpus luteum’ – meaning yellow body. Oestrogen and progesterone are released from it and alter the environment within the womb that assists the egg once it is fertilised. The uterus lining thickens and readies itself for implantation.
A nourishing liquid is produced by glands in the fallopian tube. After this, the cervical mucus congeals to prevent any more sperm reaching the egg. The corpus luteum will dissolve after approximately 10 days following ovulation in the event that no conception takes place. At the same time there is a decrease in hormones produced by the various glands and menstruation begins all over again.
You and Your Eggs
It is amazing to think that every single egg inside a woman has been there since she was an embryo herself in her own mother’s womb. The scientific name for an egg is ovum. The genetic material is contained within 46 chromosomes inside the nucleus. A protective protein membrane known as the zona pellucida surrounds the nucleus. It has its own type of yolk that supplies the embryo with vital nutrition following conception.
At the beginning of the period, chromosomes within an egg that is due to be released become active. Out of the 46 chromosomes, 23 stay inside the ovum and the other 23 adhere to a small area within the outer membrane of the egg. At the point of conception, when the sperm meets the egg, 23 chromosomes from the egg connect with 23 corresponding chromosomes contained in the sperm. This is how a child inherits characteristics from both parents as the DNA mixes. The outer membrane of the egg does not break up until the embryo becomes implanted in the uterus lining. This usually occurs approximately 4 to 5 days following fertilisation.
Historical Misconceptions About Conception
For most of mankind’s existence it has been thought that it was the man only that determined the characteristics and genetic make-up of children. The woman was seen merely as a fertile planting ground for the man to sow his seed, hence the use of the word ‘barren’ to describe women who were unable to bare children. 500 years ago, European scientists even went so far as to state that the male semen contained microscopic babies that would later develop and grow within the womb of the mother.
Scientifically, the females role in in conception and determining the characteristics of children, was not widely acknowledged, if at all until the 1800s. Obviously, things have changed a great deal nowadays to the point where a woman can conceive without even having sexual relations with the man. But the bottom line is this: a male sperm must be present at some stage or there will be no baby.
Sperm are made in the male testes. From there they travel through the penis during sexual intercourse and then via ejaculation into the vagina. The male sex organs also manufacture hormones. They are stimulated to do this by the production of LSH and FH which takes place in the pituitary gland located in the brain. These are the exact same hormones produced by women.
Located inside the testicles are seminiferous tubules in which the actual sperm are created. After they are made, the sperm are forced into the epididymis which are located at the rear of the testes. They are stored here 1-2° C below body temperature as they develop during the course of a few weeks.
Sperm themselves are swimmers and for this reason they have to function and perform their task in a fluid. This fluid in men is called semen. During periods of sexual activity and excitement, special muscles in the male sexual organs push the sperm from the rear of the testes towards the epididymis and into the seamen. This mixture of seamen and sperm exits the penis when a man ejaculates. Approximately 30,000,000 sperm are ejected at this point. Not all will be fully grown but about 75 per cent of them will be up for the job.
In the course of sexual intercourse, this mixture of seamen and sperm is aimed at the cervix. Most of the time there is a barrier formed of mucus inside the cervix which makes it impossible for the sperm to enter. But for about four days during ovulation the uterus transforms to actually provide nutrients for the sperm and sustains them for a few days.
Considering the millions of sperm that enter the vagina, at the most only a few hundred will arrive at the fallopian tube. This is where the egg is located. The sperm are hampered somewhat in their travels because of fluids inside the vagina that are acidic in nature. However, after they reached the cervix, the sperm are able to move quicker as the environment is quite alkaline in the uterus.
Not all will progress though, as the uterus itself contains cells that are responsible for combating foreign bodies and at this stage many of the sperm will be destroyed as well. If they make it to the top part of the uterus they can then gain access to the fallopian tubes. Usually only one of the tubes contains a fertile egg. So here the sperm have a 50:50 chance of getting it right, so that eliminates half of those that made it this far. The others that choose the right tube will make their way along it towards the egg. However, most will not even reach this far so it really is one lucky sperm that gets to the egg.
For the sperm to exit the man, it is obvious that he needs to have an orgasm for ejaculation to occur. Although the corresponding orgasm in the woman is not absolutely crucial for conception it does actually help the process as convulsions in the uterus can suck the sperm further towards the egg. Any sperm that make it to the fallopian tubes, where usually just one side contains a fertile egg, will encounter their target around about a third of the way down.
They are attracted, almost guided, as the egg releases compounds into the watery environment. At the same time the sperm begin to produce enzymes that enable them to bury through the protective shell of the egg. An amazing reaction occurs once the one individual sperm has managed to make it inside the egg. The egg itself immediately produces a chemical change in its surface that prevents any other sperm from entering.
That one unique sperm then carries on travelling through a thinner membrane towards the centre of the egg where the genetic material in the form of chromosomes is stored. The sperm completes its task as it buries its head into the nucleus of the egg where the two sets of male and female chromosomes fuse and form a single cell known as the zygote.
At this exact moment in time the zygote splits into, and then those two cells again divide and continue to divide until millions of cells are formed. All of this is controlled by the information encoded within the DNA and eventually a fully grown baby is formed.
But before this happens some cells within the zygote end up forming the embryo itself and others will form the placenta. This grouping of cells is known as the morula. The morula then spends the next four days travelling towards the uterus. It is assisted in this task by special cells that line the fallopian tube. At this point the tiny life is still floating free and has not yet attached itself to the wall of the uterus. It is referred to at this stage as a blastocyst.
When the blastocyst eventually reaches the endometrium, its goal is to connect to the mother’s blood supply so that it can start taking in oxygen, nutrients such as protein and glucose, and essential vitamins and minerals. As contact is made, small finger like projections known as villi, drill down into the endometrium and connect the blastocyst to the mother.
As soon as this happens growth is accelerated and the various parts of a body begin to form. Limbs begin to appear and organs are formed. The central nervous system and spine develop at a rapid pace. Hormones are produced by cells in the placenta which act as a chemical message prompting the corpus luteum to carry on manufacturing oestrogen and progesterone which build up the uterine lining. As the placenta enlarges it takes over the role of producing these hormones from the corpus luteum, which slowly reduces in size until about 2 1/2 months when it no longer plays any role in hormone production. At this point the embryo is now called a foetus and has all the appearances of a tiny person.
The danger period for pregnancy to go wrong is the time between conception and implantation and for the first 2 1/2 months. At this timepregnancies can occur. These are a result of the blastocyst implanting itself in the fallopian tube. Another problem that is very common, , occurs if a fertilised egg doesn’t implant at all. Around 70% of all conceptions fail at some stage.
We are all complete one offs. The human genome project has been trying for some years to map out the DNA of human beings. Within each of the 46 chromosomes found in every body cell are 30,000 genes so you can imagine the task these scientists have is huge. Hopefully, the advances made by the human genome project will one day lead to many breakthroughs in medical science. Already many specific illnesses and genetic disorders have had light shed on them because of this research.
The DNA that every child has within them is a result of the fusing of egg and sperm. All of the DNA encoding that the baby will ever have is created in the first few seconds of conception. It is amazing to think that at this point all the genetic information of your ancestors is contained in such a microscopic package. On top of that, this genetic history now has the potential to be passed on to future generations. Every single cell in the body contains all of these genes but not all of them are activated across the body as some are specific to various functions, such as inducing the growth of the brain, muscle tissue, bloodstream, skin etc.
There is great debate as to how much DNA affects non physical characteristics such as personality and intelligence. The extent to which these are genetically influenced is unknown. But it is a fact that anything that surrounds the baby in his or her environment will have a bearing on who they turn out to be as children and adults.
If one thing sets us apart from all the other creatures on the planet, it is our ability to make choices and to affect changes in our environment, beyond what instincts drive us to to. What a huge responsibility each and every parent has knowing that this tiny bundle of cells is so much more than chemistry in action, and that our choices and decisions will have such an impact on another life.
Having said that, it is obvious for those of us who have had several children all brought up in the exact same environment, that genetics do play a part in shaping personalities. Even identical twins can be poles apart in terms of psychological profile. Some scientists have postulated that there are specific genes to affect moods, attitudes, levels of aggression and other behaviours.
Gender of the Baby
Whether your baby turns out to be a boy or girl is determined by the X and Y chromosomes. All of the eggs inside an ovary contain the X chromosome, but the man’s sperm can have an X or Y present in the chromosome. So everything will be a combination of X from the female chromosome and either another X from the male or a Y from the male. XX results in a baby girl. And XY produces a boy. There is some evidence that Y chromosome-containing sperm swim quicker than X chromosomes sperm. It is also postulated however that the X sperm have a longer survival rate. Whether it is possible to influence the gender of a baby by a choosing went to have sex during specific periods of ovulation, has not yet been established. But some people do believe that there are certain times when X chromosome will outnumber Y chromosomes sperm and from this they try to swing the numbers in favour of one or the other to produce the desired gender.
Twins, Triplets etc.
If two separate sperm managed to fertilise two separate eggs then twins will be conceived but they will be non identical. They can either be male or female and there are no more similarities to each other than if they were born years apart.
If your family has a history of twins then you are more likely to have a chance of having them yourself because it is a genetically determined characteristic passed on from generation to generation. For whatever reason, this propensity to conceive twins also seems to kick in more after the age of 35, rather than in your younger years, though this is not a hard and fast rule.
To conceive identical twins, an egg fertilised by one sperm, must divide into two, and at the same time take all of the genetic information encoded within the DNA into both embryos. This natural cloning produces two identical children, physically speaking. Unlike the conception of non identical twins, which is influenced by genetic history, there seems to be no specific reason for the occurrence of identical twins. It seems to be down to chance alone.