4 weeks pregnant: advice, symptoms and what to expect


by Lorna White |

At four weeks pregnant, you might start to notice some symptoms. Welcome to the beginning of the embryo stage.

It’s now implantation time – the blastocyst will begin burrowing into your uterine lining, before splitting to form the placenta and the embryo.

How big is my baby at four weeks pregnant?

Your baby is still way too teeny to be seen or called a foetus yet and is no longer than 1mm - about the size of a poppy seed.

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1) Fatigue

One of the most common symptoms at four weeks is fatigue and exhaustion. Your body is growing the baby which takes up your energy.

What’s my baby doing at four weeks?

Your soon-to-be-baby has found its new home, where it will now grow for the next eight months.

It’s completed the journey from the fallopian tube to your uterus and has inserted itself into the lining of your womb.

Some women swear they can feel this happening, and report a cramping style sensation, whereas others say they had light spotting.

Shot of a young woman suffering from stomach cramps at home

As soon as that precious ball of cells has settled into its new home, it will begin splitting in two.

One half is now called the embryo and will become your baby, the other half will become the placenta, which will act as your growing baby’s lifeline for the next eight months.

This week, the amniotic sac will form around it and there are three distinct layers of cells that will grow into different parts of your baby’s body.

Your embryo might be tiny, but it’s busy! This week, the amniotic sac will form around it and there are three distinct layers of cells that will grow into different parts of your baby’s body.

The endoderm is the inner layer – think the digestive system, liver, and lungs.

The mesoderm is the middle layer and will become your baby’s heart, sex organs, bones, kidneys and muscles. And the ectoderm is the outer layer – this will form your baby’s skin, hair, and eyes.

What's happening in my body?

If you took a blood pregnancy test around this week it would be positive (for a urine pregnancy test, it might be a few days too soon).

That said, your body knows it is pregnant and is getting ready, big time!

Some women will be completely oblivious to their growing baby at this stage, others will experience some early pregnancy symptoms such as mood swings, bloating and cramping.

As the blastocyst begins to attach to your womb, around 30% of women might experience some implantation bleeding.

Midwife Lesley Gilchrist explains, "it’s extremely easy to mistake implantation bleeding for an early period as many of the pre-menstrual symptoms, such as cramps, bloating and mood changes are present with pregnancy too.

"The difference with a period and an implantation bleed is the length of the bleeding, the colour of the blood loss and the heaviness of the blood flow.

"Implantation bleeding is not a sign that there is anything wrong with the pregnancy and there are no links to implantation bleeding and miscarriage."

Within six to twelve days after fertilisation, your body starts releasing hCG – human chorionic gonadotropin.

This is the pregnancy hormone that makes that extra line appear on your pregnancy test.

Whilst we’re talking about pregnancy tests, it’s important to note, it can take over a week for your body to start producing enough pregnancy hormones to be detected.

If you’ve missed a period and had a negative test, it’s worth doing another one in a week’s time.

The best early pregnancy tests to buy: 

Clearblue Early Detection Pregnancy Test, £6.27, Amazon:

Giving you results six days before your missed period (this is the day after you expect your period), Clearblue promise over 99% accurate results.

With this test, two lines mean you’re pregnant, one line means you’re not. The results are ready in three minutes.

First Response – Early Result Pregnancy Test, £9.22, Amazon:

Fast results in three minutes, this at home early pregnancy test is a best seller and is sensitive enough to detect small amounts of pregnancy hormone.

Boots 5 Day Early Pregnancy Test, £6.99, Boots:

With a 64% accuracy five days before your period is due, the Boots Pharmaceuticals Pregnancy Test gets more accurate the closer you get to the day your period is due.

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What to do now...

Follow a healthy lifestyle:

The best thing you can do for your body and your baby is to follow a healthy lifestyle.

A balanced diet with a variety of foods, full of vegetables and fruit. You should aim to drink 8 glasses of water too.

Ask your doctor about a scan:

When you know you're pregnant you should go and talk to a doctor at a clinic.

This will be a chance for them to confirm your pregnancy and schedule an ultrasound scan.

Take me back to week 3

Take me to week 5

Did you notice any of these changes at four weeks pregnant? Let us know on Facebook or Twitter!

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