Your pregnancy week-by-week: Week Three

Welcome to Week 3! Congratulations, you are now pregnant, though you probably don’t know it yet. Egg and sperm have met and conception has occurred. Your body now begins a period of massive change, though at first those changes will be imperceptible.

Your Baby

Well done! All your hard work, ahem, has paid off and you have created an embryo that will grow to become your baby. The embryo is very tiny, too small to be seen even by ultrasound, but it’s already working hard and making big changes. During the first trimester it will grow from a simple two-cell organism to a vastly more complex baby-shaped foetus. Heart, brain, lungs and other major organs begin to develop and he (yes, baby is already a he or a she, though this is impossible to tell at this stage) is called a zygote and consists of a group of cells that are growing and multiplying rapidly as they move from the fallopian tube to the uterus. By the time it gets to the uterus the group of cells resembles a tiny ball the size of the tip of a pen and known as a morula.

The morula hollows out, fills with fluid, and becomes a blastocyst. Towards the end of the third week the blastocysts attaches itself to the lining of the womb (the endometrium), in a process called implantation. During implantation some women will experience implantation bleeding, which is usually fairly light, but can sometimes be mistaken for the beginning of a period. Implantation is a crucial time as successful implantation is very important – its success is one of the first things that will determine whether or not a pregnanct is successful. Failure to implant after fertilisation is known as a chemical pregnancy, and often goes unknown to the mother, unless she is closely tracking her attempts to conceive and has already tested postitive with a Home Pregnancy Test. In rare cases the blastocyst can implant outside of the womb, usually in the fallopean tubes, but even sometimes in the cervix, ovaries and abdomen. This is known as an Ectopic Pregancy and is a potential medical emergency. If the blastocyst does not implant, it is unlikely the pregnancy will continue.

The endometrium is reponsible for giving the developing embryo nutrients and removing any waste and the pregnancy continues, the implantation site becomes the placenta. This area begins producing  the hormone hCG (human chorionic gonadotropin), which in turn tell the ovaries to stop ovulating and triggers an increase in oestrogen and progesterone which stops the womb shedding its lining.

Occasionally, multiple eggs are released from the ovaries and are fertilised, resulting in fraternal, or non-identical twins (or in rare cases, triplets or more), known as multiple gestation. The tenancy towards releasing more than one egg when ovulating can be hereditary and results in twins that are only as alike as any other brother or sister who is born to the same parents would be. If the egg splits into two separate embryos it will become identical twins (or triplets etc.) – this type of twins will have the same genetic makeup and so will appear mostly identical.


Well, it’s happened – sperm met egg, broke through its tough outer membrane and did some fertilising. The egg then burrowed in and started to grow – yes, you’re pregnant! However, you probably don’t know it yet.

If you are trying to conceive it’s likely you will convince yourself you can feel pregnancy symptoms early on, though realistically you won’t be able to feel anything yet. However, there is now a teeny tiny life growing inside you. It may sound patronising, but it’s now your job to help your baby grow and develop, and to keep yourself fit and healthy. Pregnancy can be an amazing experience, but it can also be hard work, and definitely has its ups and downs. Once your pregnancy is confirmed (and even when you are trying for a baby) you will want to make sure you are eating well, taking prenatal vitamins and making sure you get enough of some key ingredients:

  • Folic acid – helps prevent neural tube defects such as Spina Bifida, especially important in early pregnancy while the neural tube is developing.
  • Protein – important in creating new tissue
  • Calcium – necessary for creating strong teeth and bones
  • Iron – helps support the increase of your baby’s blood volume as well as your own

For more information about eating well in pregnancy, read the Health Eating and Pregnancy article.

Your Partner

Regardless of how excited, or apprehensive you are about the idea of having a baby, chances are you’re not thinking about it as much as your partner, who may be reading too deeply into every little symptom, or getting stressed about what may or may not be. Even if her behaviour seems a little odd at times, try not to be too dismissive. Getting pregnant can be a highly emotional time, and the more you are involved, the more you learn and try to understand, the better a partner you will be.

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