Your baby's developments in the womb

0-4 Weeks

Lots happens in this crucial first month of your pregnancy. Your embryo is growing by around 0.04 inches every day and by the end of the fourth week it will be as big as the nib of a ballpoint pen with its brain, heart, lungs, liver and kidneys already starting to form.

Focus On: The Heart

By the end of the third week your baby’s first blood vessels will start to grow, but at this stage they’ll be no thicker than a strand of hair. In the fourth week the single cell that is your baby’s heart will kick-start, encouraging the surrounding cells to move to the same beat and divide into chambers.

5-8 Weeks

Over the next four weeks your baby will become a complete human being with organs, limbs and muscles, and will quadruple in length from around 4mm to 16mm long.

For the time being her head will outgrow her body. At six weeks she’s around the size of a kidney bean, but by eight weeks she’s the size of a walnut and is starting to move her tiny head and legs.

Even at this very early stage in her development your baby has already learned how to yawn, suck and swallow.

Focus On: Fetal Gymnastics

As easy as nine-weeks into her development, your baby is quite the little gymnast – using the walls of your uterus to leap around inside you.

9-12 Weeks

Your baby has now passed the most important stage in her development and she’s no longer considered to be an embryo but a fetus. Her body is beginning to catch up with her head, as her limbs straighten out and her skeleton forms.

By 12 weeks, her bones will begin to harden and her fingernails will start to grow. She’s now around the size of a squash ball and all her most important bodily structures are in place.

Focus On: Gender

By around 10 weeks your baby’s sex organs will become more obvious. If your baby’s a girl her tiny ovaries have already started to create eggs, while your baby boy’s testicles will be starting to produce testosterone.

13-16 Weeks

Your 13-week old baby is the same size as an orange and weighs around 7oz. She’s gearing up for her biggest growth spurt over the coming few weeks, when her
eyes will move closer together and her eyelashes and eyebrows will start to develop, making her look more human.

Up until now, a temporary membrane has protected her body, but she’s now growing her first layer of skin.

17-20 Weeks

You’ll probably start to feel your baby’s movements around now, although you might mistake it for indigestion to begin with. Her urinary and digestive systems are maturing and she’s practising breathing, by swallowing the amniotic fluid in and out of her lungs.

By 18 weeks her body will be covered by lanugo hair to keep her warm, and a greasy white substance called vernix will cling to her skin for protection.

Focus On: Cord Play

At around 20 weeks your baby might start playing with the umbilical cord. She’s learning how to grasp and practises by holding on to her feet, hands and cord.

She might even get it wrapped around her body, but don’t worry, it’s quite stretchy and isn’t dangerous at this stage.

21-24 Weeks

By 21 weeks your baby is around 10 inches long – half her length at birth. She weighs around 1lb and all her organs and bodily structures are fully formed, even though they’re not fully grown.

Over the next few weeks she’ll start laying down fat under her skin to keep her warm after she’s born. Even at this young age, she’s already practising her facial expressions by smiling and grimacing inside the womb.

Focus On: Ear Ear

At 24 weeks your baby’s ear is now structurally complete, although researchers believe that she might be able to hear sounds from outside the womb as early as 16 weeks.

The most prominent sounds are your heartbeat and your tummy gurgles. Encourage your partner to talk to your bump – voices with lower frequencies are believed to penetrate the wall of your abdomen more easily, so she might hear his voice better than others.

Focus On: Thumb Sucking

Your baby began sucking her thumb as early as 11 weeks, but by around 25 weeks she’ll start sucking anything she can get hold of like her fingers and toes. She’s also prone to sticking out her tongue – probably more so when you’ve eaten something sweet and your amniotic fluid tastes nice!
 
25-28 Weeks

Your baby’s first taste buds are now starting to develop and she’s drinking around two litres of amniotic fluid a day. It has no nutritional value, but helps her learn how to swallow.

She’s becoming increasingly aware of sounds and light outside the womb and if you shine a light directly on to our bump she might kick back in response.

Her eyes are now fully formed, but while she’ll open them at around 26 weeks the pigment responsible for the colour of her eyes won’t form until she’s exposed to natural light after birth.

Focus on: Her beating heart

From around 26 weeks, get your partner to press his ear to your bump – he might be able to hear your baby’s heartbeat, which is twice as fast as yours.

29-32 Weeks

Your baby is now starting to prepare for birth – her immune system is growing stronger and she has a thick layer of fat under her skin, and has lost almost all her lanugo hair.

She spends around 90% of her time asleep, but when she’s awake a loud noise might trigger her startle reflex and make her throw out her arms and legs. She kicks and hiccups like a newborn.

When she’s asleep, 4D scans show that your baby experiences rapid eye movement (REM), a sure sign that she’s dreaming!

Focus On: Music Lover

At 32 weeks your baby can recognise a piece of music and move around to the beat. Fast music will get her excited, while music with a tempo similar to a heartbeat will soothe her. She might even recognise her favourite song after she’s born!

33-36 Weeks

By 34 weeks you baby weighs around five pounds and is starting to change position to get ready for delivery. If you gave birth now your baby would stand an excellent chance of survival but her lungs aren’t yet fully developed and she might struggle to breathe on her own.

37-40 Weeks

Your baby’s lungs are now ready to start breathing air and her hearing is acute, she can taste, smell, learn and touch, although her eyesight will continue to develop after the birth.

Her head makes up a quarter of her body length, but is still small enough to squeeze through your pelvis. Your womb, which has kept your baby warm and comfortable over the last 40 weeks, has now become cramped – she’s ready to come out!