In the beginning…
Around the end of this week – about two weeks after the date of your last period – it is likely that you will conceive when ovulation takes place. The ovum, (egg) about 1/6 mm in diameter, comes up out of the ovary and is taken up into the Fallopian tube and starts its rolling journey towards the uterus. When the ovum and the sperm meet in the Fallopian tube and fertilization takes place, the newly fertilized ovum starts dividing into two cells, then four, then eight and so on. In the first few days after conception, before you know that you are pregnant, the fertilised ovum with its cells still dividing rolls down the Fallopian tube into your womb or uterus. At this stage it is called a zygote. If more than one egg is released and fertilized, you could have multiple zygotes.
The zygote has 46 chromosomes – 23 from you and 23 from your partner. These chromosomes will help determine your baby’s sex, traits such as eye and hair colour, and, to some extent, personality and intelligence. It looks a bit like a tiny raspberry. This is a crucial time in terms of starting and maintaining a pregnancy and for early development.
Two or three days later – the timing of this runs into week two – the zygote embeds itself securely in the uterine wall. It continues to burrow into the uterine wall for nourishment in this embedding process called implantation. By this time this minute ball of cells has separated into two main groups:
This is the inner group of cells. The embryo is the name given to your baby from the time of implantation into the wall of the uterus until about eight weeks after conception. It is a time of phenomenal development.
The outer group of cells will become the membranes which play their part in nourishing and protecting the embryo and will incorporate a tiny yolk-sac. They will be known as the amnion and the chorion. After it has embedded in the wall of the uterus the complete ball of cells spends a few days ‘settling in’. It continues to develop quietly but miraculously.
The placenta (afterbirth) which will nourish your baby throughout pregnancy, also begins to develop. In a few weeks the placenta will have developed enough to take over from the yolk-sac and act as a direct two-way channel between you and your tiny baby. Via the umbilical cord, it is this wonderful organ which is your baby’s link with you as he develops in utero. (See box)
What does the placenta do?
- ‘Breathes’ for the baby (fetus) by giving oxygen from the mother’s blood and removing carbon dioxide.
- Gives the baby nutrients in the same way and removes waste products.
- Stores glucose, iron and minerals until the growing baby needs them.
- Acts as a barrier to some infections.
- Gives the baby antibodies against some diseases.
We’ll refer again to the placenta later in the series.
It is likely that you will not notice anything different about your body on this first week. But, consider the hormones oestrogen and progesterone. They are high in your body at this point in the menstrual cycle because they play an important part in preparing the inside of the uterus to receive a fertilised ovum. If fertilisation has not taken place there is a fall in the levels of these hormones which result in the vaginal bleeding which we know as a ‘period’. If fertilisation has taken place, the levels of these hormones remain high and play their part in helping your body to remain pregnant. However, because of the high hormonal levels of pregnancy, your period does not appear.
For you, this is the beginning of a time of great change as your body starts adapting to being pregnant. Your mind will adjust to thinking of the enormous changes that will come into your life with the responsibilities of a baby and, at times, your emotions could feel as though they are on a rollercoaster. Many of the early feelings and changes, signs and symptoms that will happen are due to hormonal adaptations to do with pregnancy taking place in your body at this time.
By the end of the first week after conception you probably won’t know whether or not you are pregnant. You will probably have hope and expectation and will be watching for every little sign.
Next week, we’ll discuss a few early signs which are pointing you onwards. In the meantime, keep happy hopeful and relaxed. If you have any questions you can contact Sarah Buchanan via her Greatvine profile.