3weeks
pregnant

Medically reviewed by Clare Herbert, Senior midwife and team leader

Written by Chess Thomas

IN THIS ARTICLE

Highlights this week

By the end of this week, you're likely to get a positive pregnancy test!

Your baby-to-be is implanting into the lining of your uterus.

You may have early pregnancy symptoms. (But many women don't.)

Baby development at 3 weeks

Your fertilised egg is now a tiny ball of constantly multiplying cells called a blastocyst. It implants into the lining of your womb and continues to grow. Some cells will become your baby, while others will become the placenta or the amniotic sac.

The cells that are developing into a placenta have started to produce the pregnancy hormone hCG (human chorionic gonadotropin). This hormone tells your ovaries to boost production of oestrogen and progesterone, which stop your womb (uterus) from shedding its lining. hCG is also the hormone that will turn your pregnancy test positive.

Meanwhile, amniotic fluid is beginning to form in the cavity that will become the amniotic sac. This fluid will cushion your baby in the weeks and months ahead.

blastocyst which will develop into embryo and placenta

Your baby at 3 weeks

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Implantation

Pregnancy symptoms at 3 weeks

You may get food cravings early on in your pregnancy or notice that your favourite foods and drinks are suddenly unappetising. Due to changing levels of oestrogen, you may also experience a metallic taste in your mouth. Aversions to tea, coffee, alcohol, fried food and eggs are common among new mums-to-be. This can work to your advantage though, as you should not be drinking any alcohol at all during your pregnancy. Your sense of smell may also change, so you might go off scents you usually like, such as your favourite perfume.

Pregnancy hormones may also be having an effect on you, so don't be surprised if you feel tired and weepy. During the day, you may feel exhausted and struggle to stay awake. This is because your body is preparing itself to support your baby.

Your body at 3 weeks

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What you need to know at three weeks pregnant

You may feel pregnant, but it's unlikely you'll get a clear result from a pregnancy test at this stage. A sensitive test may show a faint line. But this can just leave you feeling confused, rather than satisfied or excited.

The clearest sign that you're pregnant is a missed period. Yours probably isn't due until the end of this week or even next week, depending on the length of your menstrual cycle.

I did an early test that showed a faint line, and I didn't know what to think. Waiting a few more days before testing would have saved me a lot of uncertainty!

Miriam

Your pregnancy to-do list at 3 weeks

Check out our video on the top 10 signs of pregnancy.
Low energy levels are difficult to cope with. Get tips on how to handle tiredness.
Got an embarrassing pregnancy question and no one to ask? Join our too much infoOpens a new window community group for a friendly answer.
You may receive mixed messages about whether it's safe for you to eat peanuts now that you're pregnant. Find out the latest advice from our expert.
What is the placenta and what does it do? Find out as our midwife explains why it's essential for your growing baby.

Check out the BabyCentre podcast!

The Parent Pod is BabyCentre’s brilliantly entertaining and informative podcast series. Join hosts Claire and Lucy as they walk your exciting journey with you each week from early pregnancy until your baby is 12 weeks old. Subscribe now on the usual channels. Learn more

Sources

BabyCentre's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organisations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

Bailey J. 2014. Hormonal cycles: fertilization and early development. In: Marshal J and Raynor M. ed. Myles Textbook for Midwives. 16th ed. Edinburgh: Churchill Livingstone, 91-100

Brown HL. 2016. Conception and prenatal development. Professional version. www.merckmanuals.comOpens a new window [Accessed May 2018]

Cole LA. 2009. New discoveries on the biology and detection of human chorionic gonadotrophin. Reprod Biol Endocrinol7:8. www.ncbi.nlm.nih.govOpens a new window [Accessed June 2018]

Hill MA. 2018a. Embryology: week 2. University of New South Wales Embryology. embryology.med.unsw.edu.auOpens a new window [Accessed May 2018]

Hill MA. 2018b. Embryology: placenta development. University of New South Wales Embryology. embryology.med.unsw.edu.auOpens a new window [Accessed May 2018]

Moore KL, Persuad TVN and Torchia MG. 2016. The Developing Human: Clinically oriented embryology. 10th edition. Philadelphia: Elsevier, 64. mymedicallibrary.files.wordpress.comOpens a new window [Accessed May2018]

NHS. 2017. You and your baby at 0-8 weeks pregnant. NHS Choices, Health A-Z, pregnancy and baby. www.nhs.ukOpens a new window [Accessed May 2018]