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3 weeks pregnant

Find out about what happens when you are 3 weeks pregnant, including possible symptoms and also discover the science behind conception.

Week by week stages of pregnancy: week 3

Early in week three of pregnancy is when your baby is assumed to be conceived. The egg meets the sperm in the fallopian tube and is fertilised to produce one cell with genetic material from you and your baby's father.  This cell is called a zygote.

This zygote travels down to the uterus and as it travels the cells divide and one cell becomes two, then two become four and then eight.  The cells are a solid ball at this point. When it reaches your uterus it is starting to hollow out and becomes a blastocyst which implants itself into the lining of the uterus. You are now pregnant.

As your baby’s due date is measured from the first day of your last period, you are now considered three weeks pregnant. Your zygote is 0.1cm long.

Once the egg is fertilised, and particularly after it has been implanted, chemical signals cause hormonal changes in you and among other things these stop you ovulating. You will miss your next period.

Some women start to ‘feel pregnant’ very soon after fertilisation; for others it may be another few weeks before they realise they feel different.  Most commonly, women at 3 weeks say they experience various symptoms of pregnancy including:

  • Tender or full feeling breasts often with extremely tender nipples
  • Odd metallic taste in your mouth
  • Vivid dreams
  • Feeling odd, different or pregnant which may include feeling warmer than usual
  • Tiredness that feels different from post exercise tiredness, described as exhaustion, feeling ‘wrung out’ or ‘bone tired'
  • Feeling bloated or wanting to urinate more frequently
  • Dislike of or sensitivity to certain tastes or smells, most commonly coffee
  • Light bleeding or spotting can occur
  • You may experience period-like pains at around the time of your expected  period.

At 3-4 weeks of pregnancy your blastocyst will develop into an embryo and you will have the first opportunity to confirm that you are pregnant with a pregnancy test if you wish. Find out more about the next stage of pregnancy.

Further help and information

NCT's helpline offers practical and emotional support in all areas of pregnancy, birth and early parenthood: 0300 330 0700. We also offer antenatal courses which are a great way to find out more about birth, labour and life with a new baby.

Join in with NCT on Facebook and Twitter - it's a great way to make new friends and stay in touch with old ones. Or joint our community for new parents on Google+ where you can connect with other parents online who are experiencing similar things.