Fertilisation: What to expect at weeks 1-3…

Dr Christine Catling
Dr Christine Catling
Dr Christine Catling, a midwife for over 25 years, is the Director of Midwifery Studies at UTS. She believes research, innovation and good quality midwifery are pivotal to the well-being of mothers and young families. Christine has extensive experience in antenatal education, policy development and research, and has published on workforce issues, homebirth, vaginal birth...
Created on Oct 15, 2023 · 2 mins read

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Your baby

The first week of your pregnancy is actually counted as your last menstrual cycle, and your expected due date will be counted as 40 weeks from the first day of your last period.

Fertilisation usually takes place around the end of week two, and while you might not know you are pregnant yet, your body has been working in overdrive since the moment your egg was fertilised. Within hours, the cell or zygote will split into two identical cells, and then those two split into four and so on – until the cells form a group of around 16-20 cells which is called a morula.

The cells will then eventually move towards the uterus and take their positions, each performing a specific function and eventually becoming different parts of your baby’s body and placenta. Around six days after conception these cells will become known as a blastocyst and they will burrow into the uterine lining (endometrium) where they will remain for the rest of your pregnancy.

The lining of your uterus has also been preparing for the incoming blastocyst, thickening up with extra tissue to support the growing baby. This lining would have been your next period, had conception not occurred but now your baby is ready to take up residence and get growing there instead.

How you’re feeling

You likely don’t even know you’re pregnant yet so most women report feeling fairly normal at this stage. That said, some women do say they can feel a change in their body in those very early weeks and “just know” they are pregnant, and some even report feeling nauseous, queasy or ‘off their food’ as early as week 2-3.

Weekly tip

While you might still need to wait for an exact confirmation that you are pregnant at this early stage, you should make sure you are eating healthy, abstaining from alcohol and smoking and (if you haven’t already) and start taking a pregnancy multivitamin which includes folate.

Finding out you’re pregnant can be a huge shock no matter whether you were planning it or not, so talk to someone about how you’re feeling whether that’s your partner, a friend or your doctor as the emotions that are suddenly running through your body can be overwhelming at times – both good and bad!

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