Baby Development

The growth of a baby inside the womb is truly marvellous. Check out your baby’s development by clicking on the links on the side navigation for a week-by-week description.

Or read below for a fun light reading summary.

Baby’s development week by week

She has a mysterious smile on her face as she comes back from the doctor’s appointment that she didn’t tell you she had made. She wants you to switch the footie off and sit up straight. Brace yourself, there’s going to be a lot happening over the next few months.

Week 3

Millions of your little fellers swam heroically but only one got the girl. United blissfully, her egg and your gold medal sperm have been making their way down her tubes in a leisurely fashion and have finally arrived at headquarters, where they’re going to spend the next nine months whilst getting on with the business in hand – making a BMX champion perhaps, or a racing driver. Who knows.

Weeks 4 – 5. About 5 mm, or very, very small

Showing an amazing sense of purpose in one so young, the embryo who will later call you Daddy settles down and gets stuck in. Literally. It’s already connected to her blood supply and there are already layers of cells that will become brain, lungs, gut, heart, blood vessels and all the rest of it. There’s already a head end and a bottom end. It’s probably only now occurring to her that she might be pregnant and you’re still delightfully in the dark, – but not for much longer.

Weeks 6 – 7. About 8 – 10 mm, or the size of one baked bean

Baby’s all heart now – there’s a big bulge that’s started beating the first of its three billion or so total heartbeats. And brainy. There’s a big bump where baby will later store either Brian Lara’s lifetime stats or a complete record of all the shoes and handbags she ever bought. Also in evidence are the beginnings of arms and legs, muscles, eyes and ears. All the better to hear you saying ‘tidy your bedroom.’

Weeks 8 – 9. About 2 cm, or the size of a … 2cm screw

Now officially called a fetus, we’re now starting to look like a proper person. There’s a recognisable face, and eyes, a mouth and a tongue. And teeny tiny little hands and feet with the beginnings of fingers and toes. Important internal organs are happening too – lungs, kidneys, liver are all there.

Weeks 10 – 14. About 8 to 10 cm, or the size of a tennis ball

Everything’s now fully formed, but obviously in miniature. From now until D-day it’s a matter of growing and maturing. Baby’s now begun moving about and the heartbeat is strong enough to be picked up on an ultrasound. It’s going to be harder from now on for her to disguise the fact she’s pregnant – and pretty soon that bump will start to show.

Weeks 15 – 22. About 16 cm, or about the length of a chocolate bar

Fingerprints! Hair! Eyebrows! Eyelashes! Fingernails! Toenails! She’s really going to start feeling baby kicking about now and sometimes you’ll be able to make out whether that moving bump is a foot or a hand.

Weeks 23 – 30. About 33 cm, or the length of a rugby ball

It’s a taste of things to come – baby now has a sleep/wake pattern that’s quite likely to be different from yours. Don’t be surprised if they’re up at 3am for a bit of a kick or a spot of light hiccupping. Around this time baby becomes ‘viable’ – which means they have a chance of survival if they were born right now. And – ping! – baby’s eyelids just opened for the first time. Not much to see though.

Weeks 31 – 40. About 50 cm, or the size of a … newborn baby

The bell’s just gone for the final lap. Baby’s getting nice and plump. It gets harder to turn somersaults like a couple of months ago, so we’re probably stuck upside down and getting ready for the big day. This is when people ask you if you want a boy or a girl and you say – quite honestly – ‘I don’t care as long as it’s healthy.’

Week 41 – Year 20. About 51 cm – 6 feet, or very, very large

It’ll totally change your life. Being a parent is the best experience in the world ever!