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Home   1st Trimester   4 Weeks Pregnant

You’re 4 Weeks Pregnant!

What’s Happening During Week 4:

It is uncertain how sperm finds the egg. Some think the sperm might even have a sense of smell. Once the sperm penetrates the egg and the centre of each unite, the magic of fertilization has taken place. This single cell will develop into trillions of cells, in fact to over 200 types.


At conception baby receives 23 chromosomes from the mother’s egg and 23 chromosomes from the father’s sperm. Baby’s genetic code is stored in these bundles called chromosomes and each chromosome is made of tightly coiled strands of DNA. If you lined up those DNA molecules end to end, a single cell would contain six feet of DNA!


Genes are working subunits of DNA, some are dominant and others are completely hidden. Parents make up an equal contribution to most of our genetic makeup except for the sex chromosome which is determined solely by the father. At the moment of conception much of the future of baby has already been predetermined, certain diseases, disposition, hair and eye colour, each gene or combination of genes that make us physically and genetically unique.

About a day after conception the cell divides for the first time. Every cell in the human body will need it’s own copy of the original genetic blueprint. Chromosomes produce first, making an identical copy of the genetic code. The nucleus splits and the cell divides. This division causes formation of a new structure called a zygote. After more multiplying and dividing takes place the zygote forms into a morula (12 or more cells) and continues to travel down the fallopian tube. After 4 or 5 days this tiny ball of cells arrives into the uterine cavity and at this time endometrial fluid penetrates this morula to create a central cavity. When this happens this new structure is now known as a blastocyst and is equal to 100 cells. The tissue of the blastocyst then divides into two important layers. The outer layer becomes the placenta and the inner layer the embryo. The inner cells are known as stem cells and have the capacity to turn into any one of over 200 types of cells and can grow to become any part of the body.

The embryo is starting to take shape !


Share your Thoughts
  • jessica

    Hi, I’m in week 4.i just missed my period yesterday and got the positive result on pregnancy test, I have a cramping on my left it normal?
    my first pregnancy ended up with miscarriage(empty fetus) on weeks 8 few months ago,and I had a left ovary pain from that moment and spotting that it eneded up with miscarried.i scared maybe this time happening the same thing?is it normal to have a cramping and stabbing on week 4?thanks

    • PregnancyChat

      Hi Jessica, thank you for contacting us. It is quite common to have pain in the pelvis that is not related to miscarriage in any way. The ovary that released the egg that was fertilized leaves behind the cyst of pregnancy called the corpus luteum. Sometimes this cyst can be tender. Try not to worry. Kind regards Monica

  • jessica

    thank u so much Monica. can u please tell me is it ok to drink green tea, tea,coffee during the early pregnancy?i used to drink 3 cups green tea every day before my pregnancy.can I still drink it?thanks

    • PregnancyChat

      Thanks again for writing. My understanding is 3 cups of green tea is less than 200 mg of caffeine and within the accepted amount to be consumed by pregnant moms. Please consult your doctor for advice. kind regards Monica

  • Hi thank you for this video. I am in my 4th week and I have been getting a lot of cramps and I has been really painful and I have just missed my period. I am also experiencing lower back pain and hip pain on my left side which makes it difficult to sit. I still get the feeling as if I am getting my period and I had diarrhea instead of constipation, is this normal? I feel very weak and fatigued as well, are these symptoms normal? It’s my first unexpected pregnancy, after I had started a new type of birth control, and I am scared since it feels odd.

  • TBlogger

    I had my LMP on 27 Jan 2015 and my cycle length is 35 days. We are trying for a baby and since last week i.e 18 Feb, 2015, I have tender painful breasts, feeling of tiredness and a little bit of gas problem. I have a feeling that I am pregnant but I haven’t tested yet as it’s too soon to test (period is due in 1st week of march). But today i.e. 24 Feb, my breast pain has subsided and I only feel it occasionally. Is this something to worry about or I am thinking too much?

  • Stormie O

    Hi, My name is Stormie. My husband and I have been TTC for 8 months. I am right around my expected period time. My cycle ranges anywhere from 28-42 days. Two days ago I thought my period was starting. I woke up to some light bleeding which was red and only last maybe an hour. The next day I had no bleeding at all. When I woke up this morning about 3 hours ago I had some dark red/brown bleeding that is fairly light, not heavy. I have read all about implantation bleeding and I thought thats what it was when I started bleeding a couple days ago. But I did not expect to have any more bleeding/spotting. Could it still be implantation bleeding?

  • Amy merrills

    Hi i am 4 weeks pregnant and today I had light spotting, it’s carried on throughout the day (still light) I’ve also had a bit of back pain. Can anyone help? xx