Your pregnancy: 4 weeks pregnant

Last modified on Thursday 12 May 2022

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At four weeks pregnant you've probably only just found out the good news. Whether you're experiencing some early pregnancy symptoms or are worried about early bleeding, find out what to expect, now that you're expecting.

What's happening at 4 weeks?

  • Time to take a pregnancy test this week (if you haven't already).
  • Your fertilised egg is making its way to your uterus (womb).
  • You may have some early pregnancy symptoms.
  • Implantation bleeding can occur – don't panic.

How big is your baby?

Although you’ve probably been completely unaware of it, the most fantastic things have been going on inside you.

Your weeks of pregnancy are dated from the first day of your last period. So, during week one and two, you aren’t actually pregnant – your body is just preparing for ovulation.

You then ovulate around two weeks after the first day of your period (depending on the length of your cycle) and the egg needs to be fertilised within 24 hours.


The fertilised egg (now called a zygote), starts dividing into identical cells as it makes its way from the fallopian tube to the uterus.

Around a week after fertilisation, the fertilised egg starts to implant into the lining of your womb. Right now, your baby (still an embryo) is attached to a tiny yolk sac, which provides nourishment.

In a few weeks, the placenta will be fully formed and will take over, passing oxygen and nutrients to your baby.

At four weeks pregnant, your fertilised egg is about the size of a grain of sugar.

Grains of sugar in a bowl
Your baby will be the size of a grain of sugar when you're four weeks pregnant.

What's going on with your body?

It’s quite likely you haven’t felt any pregnancy symptoms yet. Very often the first thing most women notice is that their period is late.

But, it's also possible to feel or notice some early pregnancy symptoms such as fatigue, discharge, indigestion, bloating and cramping.

Your body starts getting ready for milk production as soon as you're pregnant so it's not unusual to notice a tingling sensation in your boobs, or find that your bra feels a bit uncomfortable.

Pregnancy also increases the blood supply to your breasts, which can make your nipples particularly sensitive.

Find out more about the early signs of pregnancy.

What to expect this week: implantation bleeding

When you're TTC, there's nothing more disheartening than going to the toilet and seeing that your period has started.

But, before you grab a glass of wine to console yourself that you're not pregnant this time, bleeding around your due date isn't always bad news.

Light spotting (a small amount of blood in your knickers, or when you wipe after using the loo) at this stage of pregnancy can be what's known as an 'implantation bleed'.

It's thought to happen when the fertilised egg implants itself on the lining of your womb. It's part of the process of early pregnancy and is a good sign.

Here's three things to know about implantation bleeding:

  • the blood is usually light pink or brownish in colour (period blood is more likely to be bright red)
  • it may even look like a pink-tinged discharge
  • not everyone notices an implantation bleed – this doesn't mean you're not pregnant though.

Of course, any heavier or continuous bleeding could be your period. Don't be too disheartened though – keep trying.

If you are pregnant and experience any unusual bleeding around this stage, or if you're worries about light bleeding, see your GP or midwife.

Read more about bleeding during pregnancy, including more about implantation bleeding.

What to do this week: see the doctor

Once you've done a pregnancy test and got a positive result, it can be hard to know what to do next.

A good place to start – especially if it's your first baby – is by booking a GP appointment. Your GP can set you up with your local midwives so you'll get the right care throughout your pregnancy, and give you advice about how to get your pregnancy off to a healthy start.

Your GP can also offer reassurance if you're feeling overwhelmed or anxious – or are already suffering from morning sickness.

If you're taking any medication, they'll make sure it's safe to take during pregnancy, and offer alternatives if not. It's important to keep taking your regular meds until you've spoken to your GP. Although some medicines aren't safe in pregnancy, stopping suddenly can be bad for you and your baby.

Read more about what to do now that you're a mum-to-be.

Your 4 week to-do list

1 Take a pregnancy test (if you haven't already).

2 Take daily folic acid – 400 micrograms should be taken when trying to conceive and for the first 12 weeks of pregnancy to protect against defects, such as spina bifida.

3 Book a GP appointment.

4 Try to relax – there's a long road ahead so get in some early nights and gentle exercise while you can.

5 Find out which foods you should avoid now you're pregnant.

What to watch this week...

Get expert tips on what to expect at 4 weeks pregnant from our midwife.

What happens next week...

Want to know what happens when you're five weeks pregnant? Or maybe you've already forgotten what you read last week? Just click on the numbers above to find out more about what to expect when you're that number of weeks pregnant.

Just found out you're pregnant? Work out your due date with our handy due date calculator below ...

Due date calculator

Select the first day of your last menstrual period and the average length of your menstrual cycle

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