First trimester - Weeks 1- 3

Weeks 1 - 3

Week 1


During your first week of pregnancy, you are in actual fact not pregnant yet. This may seem confusing, but the way it works is that your doctor will begin to track your pregnancy from the date of your last period. At this point in time, your body is preparing itself for when you do fall pregnant. Your potential pregnancy will begin in your ovaries, these are two almond-like glands that are attached to the two sides of the uterus.

Your uterus is now thickening in order for it to feed and house your fertilised egg from the moment it implants to the uterus wall. Now it is time to have patience and take extremely good care of yourself, there are still a number of weeks to go and the journey is just beginning. So, in conclusion, you are not really pregnant during your first week of pregnancy, but the date your doctor will take in order to get an idea of the date of birth is from the end of your last menstrual period.

Week 2


At this stage, you may not feel different, but you are currently at your most fertile time of your menstrual cycle, this means you are ovulating!

If a sperm has managed to fertilise an egg in the fallopian tube as it makes its way to the uterus, then you are likely to conceive. If an egg is fertilised, then you may experience some light spotting a few days after this (although not everyone experiences this). This can often be mistaken for your period, but it is in actual fact a sign that the fertilised egg has now attached and implanted in the lining of your uterine wall.

Your baby’s development at this stage

You may not be pregnant just yet, however, you are about to release a mature egg that has the potential to grow into a baby.

In the previous week, your body increased the levels of oestrogen and progesterone released. These hormones were pumped through your blood stream and in turn, told your uterus to produce a nutrient-rich, lush lining of blood-filled tissue in order to support the potentially fertilised egg. While this was all happening, eggs in your ovaries were maturing in sacs filled with fluid, these are called follicles.

At around day 15 of your 28-day cycle, this is at the beginning of week two of your pregnancy, you will begin to ovulate. When you are ovulating, an egg will break away from its follicle and be sent into one of the fallopian tubes. Your day of ovulation can often vary, for example, it may occur at any time between the ninth and 21st day of your menstrual cycle.

Your egg will be fertilised if a sperm that is ejaculated manages to fertilise it within 24 hours. About 250 to 300 million sperm are present in one ejaculation and swim from your vagina into your cervix, which is normally tightly closed, but during ovulation, the cervix will open slightly allowing for an easier passageway for the sperm. The sperm that does not make it will either flow out of your vagina or perish in its acidic environment. The sperm who survive have protective elements in their surrounding fluid.  Upon entering the cervix, some of the sperm may be destroyed by the female body as they are recognised as invader cells.

The sperm will then travel through to the uterus and finally, the fallopian tubes. The sperm will divide in half before entering the fallopian tubes, one of which contains the egg and one that is barren. In the fallopian tube with the egg, one of the sperm will win the battle of the fittest and meet with your egg. Out of the 250 to 300 million sperm, only around 400 or so will survive the 10-hour trip to the egg, and from there, only one will be able to burrow in through the outer membrane of the egg. The journey of a sperm to an egg is an epic one and one that is met with incredible odds. Once a sperm has merged with the egg, the egg will change its membrane becoming impenetrable, no longer allowing any other sperm to enter it.

In the case of fraternal twins, two eggs are fertilised by different sperm. With identical twins, the fertilised egg, known as the ovum (fertilised by a single sperm), will split into two eggs to form two babies with the exact same genetic code.

In the following hours, normally between 10 and 30, the nucleus of the sperm will merge with your egg’s nucleus and their genetic material will be combined. If the sperm is carrying an X chromosome, then the baby will be a girl, if the sperm is carrying a Y chromosome, then you will have a boy. When the female genetic code merges with the male genetic code, this instantly forms a unique combination of genes that will determine, along with gender, the baby’s eye colour, hair colour and hundreds of further characteristics.

The fertilised egg will now travel from the fallopian tube into the uterus. On this journey the egg, which is now known as a zygote, meaning that it has merged with a sperm, will divide itself to form 16 cells that are identical. As soon as the egg has entered the uterus, it is known as a morula. To recap, the stages of development of the oocyte (egg) progress from an ovum, to a zygote, to a morula. After a day or so of being in the uterus, the morula will start to burrow into the uterine lining and continue its journey of transformation and growth.

So, at week two, your little baby is just a small ball of cells, this ball of cells is scientifically known as a blastocyst. This means that it has a cell mass on the inside of it that will eventually develop into the embryo, and a cavity that is filled with fluid and will develop into the amniotic sac.

The placenta forms from an outer cell mass, this is the organ that will deliver nutrients and oxygen to your baby that is vital to sustain life and also remove any waste products.

Changes in your life as your baby grows

It should be pretty clear by now that there are a number of factors that need to take place in order to conceive, therefore, timing is crucial. If you want to better your odds, then try to have sex in the two days before you ovulate and then once again on the day that you ovulate. It is best to ensure that you and your partner have enough time to make love and do not have to rush.

It is also beneficial to do some research if you are trying to conceive. Find out about how to detect and pinpoint your day of ovulation and also find out how many times it will take to get pregnant. Some couples may need a few more attempts than others.

Make sure you speak to your gynaecologist or family doctor to ensure you and your partner are able to conceive and do not have any issues.

The majority of babies are born after about 38 weeks from conception (when the egg is fertilised), however, because it is often difficult for your doctor to pinpoint the exact date of conception, assuming your menstrual cycle is 28 days, your doctor will count the number of weeks from the date of your last menstrual period. After having an ultrasound, the expected date of birth will be more accurate. 

Tests and what to do at this stage

If you are successful in conceiving, then you will get a positive result on a pregnancy test at home. As a rule of thumb, in order to obtain the most accurate result, you should only take a home pregnancy test a week after you miss your period. However, some home pregnancy tests are only accurate after three weeks. A positive result can be followed up with a blood test to confirm your results.

Your doctor may recommend you have a genetic carrier screening test to detect if you or your partner have inherited any illnesses that may be passed onto your child. Speak to your doctor about whether or not you should stop any prescription or over-the-counter medication you are currently taking (this includes herbal and natural supplements). Of course, by now, you would have stopped any birth control pills (and if not, and the pregnancy occurred accidentally, you should). It is best that you also stop smoking or drinking entirely at this stage.

The first sign of pregnancy – breast changes

Tender and swollen breasts are normally the first indicator of pregnancy, this may also be accompanied by feelings of fatigue. From the moment of conception, your breasts will begin to prepare for their vital job of producing breast milk. Have a look at our article on the symptoms of pregnancy to find out more about them.

Week 3


Congratulations, at week 3 you are finally pregnant! By now, there has been a momentous meeting that has happened inside of you, where the single sperm, through a journey like no other, has finally managed to merge with your egg and fertilise it. A few days later, your fertilised egg is now in the uterus and has begun to burrow into the uterine wall – your baby is in the process of being formed.

Your baby’s development at this stage

Your baby, which is now just a small ball of cells, known as a blastocyst. Inside of this blastocyst, there are a couple of hundred cells busy multiplying at a rapid pace as your baby begins to develop and grow. The part of the blastocyst that will form into the baby’s placenta has begun to produce the hormone known as the pregnancy hormone, human chorionic gonadotropin (hCG). This informs your ovaries that they do not need to release any more eggs, and the production of oestrogen and progesterone are triggered. Oestrogen and progesterone are responsible for not allowing the uterus to shed its lining, as well as the egg that has now attached to the lining and also stimulate placenta growth.

While all of this is happening, amniotic fluid has begun to form around the blastocyst, that will soon turn into your baby’s amniotic sac. This is a cushion-like fluid that will protect your baby in the upcoming months.

During this stage, the blastocyst is receiving nutrients and oxygen, as well as discarding any waste through a simple circulation system that is made of tiny tunnels connecting the blastocyst to blood vessels in the wall of the uterus. The placenta will only be at a point of development to do this job at the end of your fourth week. 

Changes in your life as your baby grows

Now that you are finally pregnant and have a little baby inside of you, you should:

  • Stop smoking (also avoid second hand smoke)
  • Stop drinking alcohol
  • Avoid caffeine
  • Avoid any illegal drugs
  • Speak to your doctor about any prescription or other medications you may be taking
  • Inform your dentist or any other specialists that you are pregnant
  • Drink plenty of liquids and water
  • Stick to a healthy and nutritious diet

Tests and what to do at this stage

If you haven’t already done one, you should do a home pregnancy test. If you have a positive result, then make an appointment to see your doctor and speak to him or her about preparing for pregnancy.

You should also be taking a prenatal vitamin that contains about 400 micrograms of folic acid, this can be bumped up to 600 if you are officially pregnant and this should be taken daily.

What should I eat when I am pregnant?

The phrase “you are what you eat” should be old news by now. Therefore, your diet has a direct impact on the health of your unborn baby. As well as this, what you eat in the next nine months will have an impact on your own as well as your baby’s health for the next few years. The easiest way to go about eating for pregnancy, is to follow these 10 steps:

  1. Make sure you are getting enough folic acid – This is important when you are trying to conceive and when you are actually pregnant.
  2. There is no such thing as eating for two – Speak to your doctor about how much weight you can expect to gain through the pregnancy, this is normally due to the size of your baby and the amount of blood in your body increasing and should not really be due to gaining fat due to poor eating choices or “eating for two”.
  3. Make sure you include omega-3 fatty acids in your diet – These are found in fish and in tablet form and can help in the development of your baby’s brain, vision, motor skills and memory in their early childhood.
  4. Stay clear of alcohol – This should already be pretty clear as alcohol can have adverse effects on the development of your baby and regular consumption may result in foetal (fetal) alcohol syndrome.
  5. Try to avoid raw foods – Raw fish, eggs, meat and unpasteurised milk can contain a harmful bacterium such as E. coli and Salmonella. This kind of bacteria can have a negative impact on the development and birth of your baby.
  6. Make sure you get enough iron – When you are pregnant you will need about double the amount of iron you usually would, which is about 30 milligrams a day. This helps to support your blood volume increase and also benefits your baby enabling him/her to get enough oxygen as iron helps to transport oxygen.
  7. Follow a high fibre diet – Make sure you are eating enough fresh fruits and vegetables and trash any junk food that has a high sugar or oil content. Fruits and vegetables are packed with minerals and nutrients that your baby will greatly benefit from.
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