​How your baby develops week to week

The first 8 weeks

The first 2 months are when your body gets ready for the changes that pregnancy brings. It’s also the time when your baby’s brain, heart, bones, blood vessels and organs develop.

The sex of your baby and colour of their hair are determined when you conceive and before you even know you’re pregnant.

First 4 weeks

By the end of the first week:

• if you conceived naturally, the fertilised egg (also called a blastocyst) has made its way along your fallopian tube and attached itself to the lining of your womb
• if you had assisted conception, the fertilised egg will already have been planted in your womb

When the blastocyst’s strongly fixed to the lining of your womb it’s called an embryo. It’s about the same size as a full stop.

The cells on the outside of the embryo start to link with your blood supply, so your baby can get everything they need to grow. This link develops into the placenta, which is attached to your baby by a cord.

How your baby’s growing

Your baby’s growing at a faster rate than at any other time in your pregnancy, but they’re still difficult to see without a magnifying glass.

Your baby’s spine starts to grow very early in your pregnancy – often before you know you’re pregnant.

Folic acid

Folic acid (folate) helps:

• your baby’s spine to develop
• prevent neural tube defects, such as spina bifida

If you’re not already taking folic acid, now’s the time to start.

More about taking folic acid in pregnancy

Week 5 to 8

Your baby’s spine starts to grow very early in your pregnancy – often before you know you’re pregnant.

Folic acid

Folic acid (folate) helps:

• your baby’s spine to develop
• prevent neural tube defects, such as spina bifida

If you’re not already taking folic acid, now’s the time to start.

More about taking folic acid in pregnancy

Week 5 to 8

By week 5 to 8 you may start feeling:

• very emotional as pregnancy hormones start to kick in – this is common and it’s normal to feel low one minute and happy and excited the next
• very tired – some women feel more exhausted in early pregnancy than at any other time

You may start feeling sick around week 6 – although some women go through pregnancy without feeling sick at all.

More about morning sickness

Look after your mental wellbeing

It’s just as important to look after your emotional wellbeing as it is your physical health. It’s okay to not feel okay about being pregnant.

There’s lots of help and support for mums to be and partners, so you don’t need to manage alone. Talk to your partner, midwife or a friend about how you’re feeling and get help if you need it.

How your body’s changing

You may start noticing:

• your hair getting thicker
• some foods can start to taste different, and what you like or dislike may change
• you need to go to the toilet more often – your womb’s now twice the size it was and is pushing on your bladder
• your breasts feel heavy and tender as they start developing the tissue that will make and store your breast milk

How your baby’s growing

Your baby’s still tiny but growing quickly. They grow from the size of an apple pip at week 5, to about the size of a raisin at week 8. They’re starting to look a bit like a tadpole, but the tail will disappear and become the bottom part of their back.

Your baby’s growing from 3 layers:

• the first layer becomes the nervous system and brain
• the second layer will be the major organs, such as the digestive system and lungs
• the third layer will be the heart, blood system, muscles and skeleton

By week 5 their heart and blood vessels are just starting to form.

By week 7 their heart’s started to beat. Tiny buds are developing that will become their arms and legs.

By the end of the week 8, your baby has tiny hands and feet with webbed fingers and toes, and their lungs have started to grow.

Your baby’s movements

Your baby’s floating inside the amniotic sac (bag of waters) which will protect them throughout pregnancy.

They may start to move around now, but you won’t feel any movement for a while yet.

More about how your baby moves

Week 9 to 16

By week 9 you don’t look pregnant yet, but your waistline may be changing and your breasts are probably getting bigger.

Now’s a good time to get measured for a new bra to make sure you’re getting enough support.

How your baby’s growing

Your baby:

• is about 2.5 cm long from the top of their head to their bottom
• has eyelids, but they’ll stay closed for a few weeks yet

The ends of their arms and legs are starting to look like hands and feet.

Measuring your baby

Your midwife will measure your baby’s growth at each antenatal visit.

To do this, they’ll measure your tummy from the top of your pubic bone to the top of your bump. This is called the fundal height. They might also do a growth scan.

The measurements are put on a chart and checked to make sure your baby’s growing well.

Week 10 to 11

By week 10 and 11 you’ll probably feel hungrier than usual because it takes a lot of energy to grow a baby.

Most women have an ultrasound scan about now, so you’ll be able to see your baby for the first time.

More about early pregnancy scans

How your baby’s growing

Your baby is about 4 cm long from head to bottom and weighs about the same as a large grape.

Their:

• arms and legs are getting longer
• elbows bend
• fingers and toes are beginning to lose their webbing
• heart’s fully developed and beating, but your midwife can’t hear it yet
• head will look big compared with the rest of their body – but don’t worry, their body will catch up

Week 12

By around week 12 some women start to get a small bump.

More about screening tests in pregnancy

How your baby’s growing

Your baby:

• will have their own special fingerprints
• can wave their legs and curl their fingers and toes, but you won’t feel this yet
• will have 20 little buds which will become their teeth

Fetal growth restriction

Sometimes antenatal checks pick up that a baby’s smaller and lighter than they should be for the stage of pregnancy. This is called fetal growth restriction.

Most small babies are born healthy and grow into healthy children, but if they do have fetal growth restriction they’ll need extra care during pregnancy.

More about fetal growth restriction

Week 13 to 14

By week 13 and 14 if you’ve had morning sickness it should be starting to get better, but for some women it carries on longer.

You may start to see a dark line appearing from your tummy button to your pubic hair. This is called the linea nigra.

How your baby’s growing

Your baby is about 7 cm from head to bottom and now looks much more like a baby.

Their:

• ears have developed but they can’t hear yet
• liver, kidneys, digestive system and lungs are all developing

They now get all the energy and nutrients they need from you through the placenta.

Week 15 to 16

By week 15 and 16 you may have that pregnancy glow, and your:

• hair looks thicker
• skin’s more plumped out
• bump’s probably starting to show
• usual clothes will feel tight

You might just have started to feel your baby move inside you, although this doesn’t usually happen until later.

If you had been feeling sick this should start to pass. Your breasts should feel less tender too.

How your baby’s growing

Your baby’s body is growing fast to catch up with the size of their head.

They:

• have fine, downy hair called lanugo on their body that will go before they’re born
• can suck their thumb
• can move all of their arms, legs and joints

​​Week 17 to 24

By week 17 and 18 you may be able to:

• hear your baby’s heartbeat when your midwife examines you
• feel your baby moving around (it may feel like bubbles or wind)

Your baby’s probably kicking and moving around a lot, especially at night. Don’t worry if you can’t feel anything yet.

How your baby’s growing

Your baby’s about 13 cm from the top of their head to their bottom.

Their taste buds are beginning to form.

Week 19 to 20

You’re halfway there, so it may be now that it really sinks in that you’re going to be a parent.

You may feel:

• soreness (pain) in your back
• more tired
• hungrier, so have healthy snacks like fruit or nuts ready

You might also feel your baby kick and move, though if you allow someone to put their hand on your tummy they might not be able to feel it.

You’ll be offered a second ultrasound scan at about this time.

More about mid-pregnancy scans

Scotland’s Baby Box

The Baby Box is a welcome gift for every baby born in Scotland. It can help you get ready for the arrival of your baby and gives them a safe and comfortable place to sleep if safe sleeping guidelines are followed.

Your midwife will help you register for a Baby Box when you’re about 20 to 24 weeks pregnant.

More about the Baby Box

How your baby’s growing

By week 20 your baby’s about 25.5 cm from head to toe and very active.

They can grasp with their hands, and their:

• second teeth are beginning to form behind the first ones
• body starts to be covered with a white sticky substance called vernix, which forms a greasy waterproof layer on their skin

Week 21 to 22

As your baby grows, and your bump gets bigger, some women have difficulty sleeping. This may cause a bit of absentmindedness or forgetfulness. This is normal and nothing to worry about.

Some women also:

• get indigestion – speak to your midwife if this is troublesome
• have the odd leak of urine – so now is also a good time to start pelvic floor exercises if you haven’t already

How to do pelvic floor exercises

How your baby’s growing

Your baby weighs about 500g, and:

• their eyebrows and eyelashes are growing
• they can hear sounds both inside and outside your body – if you chat to them they’ll get to know your voice and they might kick in response or quieten down to listen

Week 23 to 24

By week 23 and 24 it’s normal for some women to have:

• backache
• varicose veins
• constipation
• leg cramps

You might also:

• develop skin tags (little bits of extra skin) at places where your clothes rub – these are nothing to worry about
• have rashes or spots
• find that your nipples, freckles and moles get darker

More about common health issues in pregnancy

Sleeping

From 24 weeks you should start going to sleep lying on your side. Don’t worry if you wake up lying on your back, just roll on to your side again.

It doesn’t matter if you lie on your right or left side.

How your baby’s growing

Your baby:

• has skin but no fat (so they’ll look a bit wrinkly) – they’re going to quickly put on weight over the next 4 weeks
• can hear well and can make out noises such as a rumbling stomach and your heartbeat, and outside noises such as music, voices and the vacuum cleaner

You should feel your baby move every day from about week 24.

More about your baby’s movements

Week 25 to 32

By week 25 and 26 you’ll be walking differently because your centre of gravity’s changed. Your feet, ankles and fingers might be swelling too, so sit with your feet up whenever you can.

It’s normally perfectly safe to have sex when you’re pregnant, but you and your partner might find that your desire for sex changes.

Sleep on your side

In the last 3 months of your pregnancy, go to sleep lying on your side. Don’t worry if you wake up lying on your back, just roll onto your side again. It doesn’t matter left or right side.

How your baby’s growing

Your baby’s:

• practising making breathing movements, but their lungs aren’t completely developed yet
• moving about a lot, which might feel like rolling, jabs or stretching

Everyone’s different, so:

• get to know what your baby’s movements feel like
• try to work out when your baby’s most active, so you can get to know what they’re doing and how much they’re moving

Your baby’s movements

If your baby’s moving less or the pattern of their movements has changed it could be a sign of a health issue.

The sooner you pick up these changes, the sooner you can get the right treatment if there’s something wrong.

Week 27 to 28

At week 28 you’re into your third trimester.

Because your baby’s aware of voices, you and your partner or family members can talk, sing and play music to them. Finding a quiet time to do this helps you to bond with your baby and your baby feel safe and secure.

Braxton Hicks contractions

A Braxton Hicks contraction is when you feel your abdomen tightening for about 30 seconds, several times a day. This can easily be mistaken for labour, but they’re different from labour contractions.

Braxton Hicks contractions can start happening from around week 28 onwards.

More about Braxton Hicks contractions

How your baby’s growing

Your baby’s chances of surviving outside the womb are increasing week by week.

They’re:

• developing some fat and muscle, and look less skinny
• beginning to remember things

They might begin to open and close their eyes, and can:

• turn their head towards a bright continuous light
• smell, taste and hear more as their brain’s growing quickly

Week 29 to 30

By week 29 and 30 some women are uncomfortable lying down at this stage. If you’re finding it hard to sleep, try a cushion between your knees or at your side.

If you’re getting backache as your baby grows, try some gentle massage and make sure your posture’s good.

How your baby’s growing

Your baby’s:

• about 40 cm from head to toe
• making breathing movements more regularly, and may surprise you if they’ve hiccups

The fine hair (lanugo) covering them may be starting to fall out.

Week 31 to 32

By week 31 and 32 you may have indigestion or feel a bit out of breath. This is caused by the pressure on your stomach and lungs as your baby gets bigger. If this happens don’t worry. Your baby’s getting the oxygen they need from the placenta.

You may have some stretch marks as your bump grows. These can look quite discoloured but will fade to become faint, silvery lines.

Your Baby Box should have arrived. This usually happens 4 weeks after your register.

How your baby’s growing

Your baby’s about 42 cm from head to toe and putting on weight.

Their lungs have formed and are developing. They may also be dreaming while they’re asleep.

Week 33 to 40

By week 33 and 34 your breasts may be leaking colostrum to get ready for breastfeeding, but this doesn’t happen to everyone.

If you’ve got varicose veins, then resting with your feet up may help your legs feel better.

It’s common for women to feel puffiness in their feet, ankles and fingers, but if your face is swelling too, tell your midwife, GP or the hospital.

More about common issues in pregnancy

How your baby’s growing

Your baby’s lungs are now fully developed, and they:

• can feel you touching them when you rub your tummy – if you see a bump, it might be their hand, foot or elbow
• can do all sorts of things, such as sucking and grabbing
• might be lying head down now to get ready for being born

Week 35

By week 35 you’ll probably be feeling tired. As there won’t be much time for rest after the birth, try to get as much as you can now.

Take some gentle exercise, such as a walk or a swim, to help you relax and make it easier to sleep.

You should be thinking about things you can do, read or ask your midwife about now. This will help you feel as ready and confident as possible to be a parent when your baby arrives.

More about preparing for parenthood and caring for your new child

How your baby’s growing

Your baby weighs about 2.3 kg and is still putting on weight.

Their toenails and fingernails could almost do with a trim

Week 36

Your bump’s getting lower (called lightening) as your baby gets ready to be born.

Your baby’s head may be engaged, which means the widest part has moved down into your pelvis. Don’t worry if their head doesn’t engage at this stage as some babies don’t until labour starts.

How your baby’s growing

Your baby probably weighs about 2.7 kg. They’re also still moving every day, but have less room to move around now.

Week 37 to 40

By week 37 to 40 you might be getting stronger and more frequent Braxton Hicks contractions.

You can help to ease any discomfort by:

• focusing on your breathing, as if you’re in labour
• lying down on your left side

Taking a gentle walk will be good for easing any aches and pains.

Plan for the birth

Many babies arrive earlier or later than their due date, so make sure your bags are packed and you’re ready when baby is.

More about packing for the birth

How your baby’s growing

Your baby’s now fully developed and ready to be born. They’re:

• putting on about 14 g in weight every day
• still covered in vernix, but the lanugo has gone