The 4th week of pregnancy

Your body is telling you that you are pregnant, you may have missed your period (monthly menses) and may have had a pregnancy test to confirm you are pregnant. By this 4th week of pregnancy your embryo is 14 days old and you may be experiencing some physical changes.

Couple sat in joy with pregnancy test result

The signs of pregnancy can vary between women. These are the most common ones:

  • Unexpected tiredness: the changes in your body can cause fatigue. It's normal to feel more tired now.
  • Change in mood: it’s normal to feel elated and scared.
  • Morning sickness: pregnancy sickness - whether just in the morning or during the day - affects many pregnant women and is most common in the first trimester.
  • Tender and sensitive breasts: you may find that your usual bra is uncomfortable, and your breasts are more sensitive to touch.

Is pregnancy already detectable in the 4th week?

Thanks to the hormone human chorionic gonadotropin (hCG), pregnancy is usually measurable in the 4th week of pregnancy. A standard pregnancy test from your pharmacy may give you a positive result that you can then follow up with your doctor.

Your baby’s development in the 4th week

The fertilised egg now consists of more than 100 cells. It is now called an embryo. In the 4th week, your 14 day-old embryo has settled and embedded in the lining of the womb.

What happens in the 4th week of pregnancy

  • The placenta forms into an organ interwoven with blood vessels that connects your baby to your circulatory system.
  • The embryo’s primitive brain and neural stem (spinal cord) are forming1
  • The implanted embryo is now 1-2 millimetres in length1- just about the size of a poppy seed.

Here's what you should be aware of:

  • If you haven’t done so already, make an appointment with your doctor.
  • In consultation with your doctor, discuss any supplements you are advised to take, such as folic acid.2

1 Moore KL et al., editors. The developing human: Clinically oriented embryology. Eleventh edition. Edinburgh: Elsevier; 2020.

2 World Health Organization (WHO). Integrated Management of pregnancy and birth: Standards for Maternal and Neonatal Care. Geneva, Switzerland; 2007 [cited 2021 Nov 16].

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