Tommy's PregnancyHub

4 weeks pregnant - all you need to know

Congratulations on your exciting news! Tommy’s midwives are here to guide you through every stage of your pregnancy and help you get to know your growing baby.
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Tommy’s midwives are here to support you by telling you everything you need to know about week 4 of pregnancy: advice on common pregnancy signs, practical actions, such as the ‘booking’ appointment and what’s happening with your baby.

Before week 4

Congratulations on your exciting news! If your periods are usually regular, conception is likely to happen in the middle of weeks one to four. You are very unlikely to know you're pregnant at this stage.

It may sound odd but pregnancies are measured from the first day of your last period rather than the day you actually conceived your baby. This is because it's not always easy to be sure of the exact date you became pregnant.

“I spent the entire week my period was due running to the loo, just to double check I didn’t have my period. My boobs felt tender - but that can be a sign of PMT too. I took an early test in the end and couldn’t believe it when it showed positive.” Ayida, mum of one

Although a fertilised egg may have implanted in your womb just two weeks ago, if the first day of your last period was four weeks ago, you are officially four weeks pregnant! This may seem odd if you think you can definitely date the pregnancy more recently.

Get weekly updates on your baby's development from our expert midwives straight to your inbox.

What does my baby look like?

The tiny person inside you is the size of a poppy seed. A little dot, measuring about 2mm.

The baby may be miniscule but big things are happening! The fertilised egg has snuggled into the side of your womb. It divides into layers of cells that will eventually become different parts of your baby’s body.

Your baby’s nervous system and heart are developing. Amazingly your tiny dot already has some of its own blood vessels and blood is starting to circulate. A string of these blood vessels connects you to your baby. This will eventually become the umbilical cord.

Right now, your poppy seed is known as an embryo. They get their energy and nourishment from a yolk sac (until the placenta takes over in a few weeks). Your baby is surrounded by amniotic fluid within the amniotic sac, providing a comfy cushion for them throughout your pregnancy.

Your symptoms - what happens in week 4

Early symptoms of pregnancy

Bleeding or spotting

You might notice some very light bleeding, or ‘spotting’, known as implantation bleeding. This can be caused by your little seed burrowing into the lining of your womb. It often happens around the time your period would have been due and is relatively common.

You may also have some period-like cramping in these early weeks.

If you notice any bleeding at any stage of your pregnancy, though, it's important to get it checked out by your doctor or midwife.

Sore boobs

This week, a surge in progesterone can start to make your boobs feel tender, heavy and sore - a bit like how they might feel before your period.

Remarkably, these are pregnancy hormones already preparing your body to produce milk. This tenderness usually eases off by the end of the first trimester.

Find out how to deal with first trimester pregnancy complaints or read more early pregnancy symptoms here.

Things to do in week 4

Smoking and alcohol in pregnancy

It’s time to quit cigarettes and alcohol. Both can be harmful to your growing baby because the toxins pass through the placenta.

Here’s our guide to avoiding alcohol during pregnancy.

Find out more about the effects of smoking in pregnancy.

And if you’re still struggling to stop smoking, these ten steps towards quitting could help.

If you use street or recreational drugs, stop or ask your doctor for advice on stopping safely.

STIs

Sexually transmitted infections (STIs) such as chlamydia, gonorrhoea, syphilis and genital herpes can affect your baby's health during pregnancy or birth.

If you think you or your partner might have an STI, go for a check-up as soon as you can. Your doctor or midwife can tell you where you can find your nearest sexual health clinic.

Don't worry, nobody will judge you and it's important to be checked as soon as possible.

Continue (or start) taking these supplements

There are two vitamins that are very important in pregnancy and that you can take as supplements: Folic acid and vitamin D.

Folic acid is naturally present in leafy vegetables, fruits and berries, beans and wholegrain products - but keep taking folic acid supplements too, until at least week 12 because you can't get enough through food alone to build up the level of folic acid that your baby needs.

Folic acid helps in the formation of your baby's nervous system and reduces the risk of spina bifida, which is where the baby's spine doesn't close up properly.

You should take:

  • 10 micrograms of vitamin D each day throughout your pregnancy and if you breastfeed
  • 400 micrograms of folic acid each day – you should take this from before you are pregnant until you are 12 weeks pregnant

Find out more about important supplements in pregnancy.

Tell the GP you are pregnant

Once you know you’re pregnant, make an appointment to see your doctor or a midwife to get any advice you need and to be booked in for your pregnancy care appointmentspregnancy care appointments. If you make a GP appointment, they will set you up for midwife appointments or you can call the maternity unit in the local hospital and refer yourself that way.

However you book it, your first appointment with the midwife will not take place until after week 8, the ‘booking’ appointment. This can make it an anxious time but reading through these dos and donts of pregnancy may help.

This is an important time to talk about any health issues you have to make sure your pregnancy goes well. It is very important to tell your doctor about any medication you may be on, especially long-term medicines for conditions, such as asthma, epilepsy, mental health conditions, diabetes, hormone therapy, heart problems and so on. Your doctor can make sure you are on the safest medication for you and baby.

It is very important that you do not stop taking medication without talking to your GP or specialist

Find out what questions you'll be asked at the booking appointment.

If you have an existing mental health problem

If you have a pre-existing mental health condition and take medication, tell your doctor and the person who prescribed the medication that you’re pregnant as soon as possible.

They will talk to you about whether your medication is safe in pregnancy or whether you should consider a different treatment.

Find out more about your mental wellbeing in pregnancy.

What are my chances of miscarrying?

It’s a sad thing to think about, but up to one in five pregnancies will end in miscarriage in the first three months.

If you do have light bleeding, spotting or stomach pains, this doesn't mean you are going to miscarry. However, you should always speak to your doctor or midwife and ask for advice.

Find out the other symptoms you should contact your midwife about.

1. NHS Choices.You and your baby at 0–8 weeks pregnant, NHS Choices: http://www.nhs.uk/conditions/pregnancy-and-baby/pages/pregnancy-weeks-4-5-6-7-8.aspx#close (Page last reviewed: 28/02/2017 Next review due: 28/02/2020)

2. NHS Choices. Vaginal bleeding in pregnancy http://www.nhs.uk/conditions/pregnancy-and-baby/pages/vaginal-bleeding-pregnant.aspx (Page last reviewed: 26/01/2018  Next review due: 26/01/2021)

5. NHS Choices. Signs and symptoms of pregnancy http://www.nhs.uk/Conditions/pregnancy-and-baby/pages/signs-and-symptoms-pregnancy.aspx (Page last reviewed: 06/10/2016 ;Next review due: 06/10/2019)

Review dates

Last reviewed: 22 June, 2021
Next review: 22 June, 2018