Stages of baby development during pregnancy

We’ve just explored the different stages of pregnancy and how your body changes during each of these – but what about your baby? How are they developing throughout the pregnancy?

First trimester

Week 1
The week following your last menstrual period is actually called week one of pregnancy as this is when your body is preparing itself for ovulation and to create a new life.

Week 2
This is when the magic happens if you fall pregnant. You’ll ovulate and hopefully your egg meets sperm and a fertilised zygote forms.

Week 3
A few days after fertilisation, several hundred cells, which are multiplying quickly, make up the tiny ball that will soon develop into a baby and the placenta.

Week 4
Crucial things happen now! This is when that little ball of cells (scientifically called a blastocyst) implants itself into the lining of your uterus as well as forms the placenta.

Week 5
Your little empbryo is about the size of an orange seed by now and the elementary parts, such as heart, brain and spinal cord, are developing quickly. Around this time, many women start to suspect they are pregnant.

Week 6
Your embryo’s head and face are taking shape, as well as kidneys and lungs. Also, their tiny heart is beating away at roughly 110 beats per minute!

Week 7
At this stage, much of the growth is occurring in the head and the brain. While still an embryo with a small tail, the arms and legs develop hands and knee sections.

Week 8
That tail is about to disappear and facial features like a nose and eyelids are forming. And while you won’t notice it for a while, your baby is now starting to twitch and move around.

Week 9
Tiny features like the ears and toes are growing and become visible. At the same time, essential organs like the kidneys and lung keep developing. And with the movement they’ve recently started, they start to form tiny muscles.

Week 10
Your baby has now officially developed into a foetus and is starting to take on a human form. With a size of a prune, organs are now in place and they are now forming bones and cartilage.

Week 11
Hands and feet have now developed complete fingers and toes and your little foetus can open and close their hands into fists. Hair follicles start to form all over their body.

Week 12
This is a mile stone as your foetus has now developed most of their body! From now on they are just maturing and growing. Their kidneys start to produce urine and their bone marrow white blood cells.

Week 13
This is the last week of the first trimester! Your baby now has formed fingerprints and is developing vocal cords. To keep up with your baby, the placenta is also growing.

Second trimester

Week 14
To keep warm, your little baby now has a coat of downy hair on their head and body. They are also starting to be able frown and squint.

Week 15
Your baby is now practicing baby skills such as moving arms and legs, and breathing and swallowing. They are forming taste buds and can sense light.

Week 16
By this stage, your baby’s senses develop fast. Their eyes can make small movements and their ears have formed bones making it possible for them to start to hear your voice.

Week 17
Body fat is beginning to form and most of your baby’s survival reflexes are being worked on now. Their skeleton is also growing from cartilage into bone.

Week 18
Brain cells and the nervous system are developing further and your baby’s hearing grows more acute. They are also able to yawn and get hiccups from now on.

Week 19
Your baby is roughly the size of a mango at this stage and their sexual organs should be almost fully formed by now.

Week 20
You are halfway there! While your baby has grown a lot in the last few weeks, they still have lots of room in the womb in which they will move around and twist and turn a lot.

Week 21
Neurons connect further to give your baby more control over their movements. Their taste buds also get a daily workout as they start to swallow a little bit of amniotic fluid which tastes differently depending on what you’ve eaten.

Week 22
While they still have closed eyelids, your baby can perceive light and dark better than before. They can also better hear your voice and your heartbeat.

Week 23
Your baby’s skin has red tone to it because of developing veins and arteries but thanks to their fattening up at this stage of pregnancy, their skin won’t be so see-through anymore.

Week 24
Their face is almost fully formed by now, including the eyelashes, and their organs, bones and muscles keep growing and developing at a fast rate.

Week 25
Nose, nostrils and lungs are hard at work now. While there’s no air in the womb, your baby is still figuring out how breathing works in order to be ready to draw their first breath.

Week 26
At this stage, your baby starts to open their eyes! Up until now, they have been closed in order to protect the still developing and fragile retina which is now ready.

Week 27
Baby’s taste buds are well developed now and you may get a reaction to the food you eat in the form of hiccups. Also, the nerves to ears let your baby recognise both your and your partner’s voice so read bub a story!

Third trimester

Week 28
The last trimester is here! As baby’s eyes have recently open, they practice blinking and other important things such as sucking their fingers and coughing.

Week 29
In order to make room for a growing brain, their head is also growing. Your baby is also responding to stimuli such as movements and sounds from the outside world.

Week 30
That downy coat of hair is starting to disappear, their brain is growing smarter by the day, and their bone marrow is making red blood cells. All in all, your baby is gearing up for the real world!

Week 31
Your baby’s senses keep developing and they can now perceive signals from all five senses. Your baby is also establishing more set times for sleep and for being awake.

Week 32
Baby is now stocking up the fat and their skin is no longer transparent. And while you’re still weeks away from due date, your baby may start to turn their head down in preparation for the birth any time from now on.

Week 33
Your baby is now starting to be able to tell the difference between day and night. Also, their immune system is forming to prepare them for the real world.

Week 34
Important bodily functions such as their lungs and nervous system are developing further into maturity now.

Week 35
Their brain is still growing fast making their head grow heavier. It’s getting snug in there now as your baby is growing bigger every day and is roughly the size of a pineapple!

Week 36
Your baby is almost ready for the outside world with most systems fairly developed. While still maturing, growth slows down to allow the baby to move through the birth canal in a few weeks.

Week 37
Brain and lungs keep maturing and your baby is accumulating more fat. They also keep practicing stretching, rolling and thumb-sucking.

Week 38
Fine-tuning of the brain and nervous system takes place now to prepare for birth. Your baby probably has a firm grip by now!

Week 39
Your baby is officially full term now and physically ready to enter the world. Contractions are likely to set in but you may have to wait a few more weeks until actual labour.

Week 40
You’re so close now! Both you and your baby should be ready to meet each other any day as they are fully formed and developed and ready to enter this big wide world.

Stages of baby development during pregnancy

As you can see, you and your baby are very busy for the first forty weeks together – and you will be for many years to come! Remember that every pregnancy is unique and this is just the generic progression. Always discuss any concerns you may have with your doctor, no matter how small you believe them to be!

2 responses to “Stages of baby development during pregnancy”

  1. electricity says:

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    a little Ьit further. Appreciate it!

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