Your baby is a tiny ball of cells, around 1 to 2mm across – about the size of a poppy seed – and it has just settled into the lining of your womb.

Some cells will become your baby, while others start forming the placenta, which will carry oxygen and nutrients to your baby for the rest of your pregnancy.

Your baby is now about 2mm long, roughly the size of a sesame seed.

The neural tube, which becomes the brain and spinal cord, is forming, and the cells that will make up the heart are starting to come together.

Your baby is around 4 to 6mm long – about the size of a lentil.

A tiny heart is beginning to beat, and on an ultrasound scan this can often be seen as a gentle flicker. Small buds that will become arms and legs are appearing.

Your baby is about 1cm long, roughly the size of a blueberry.

The arm and leg buds are growing, the brain is developing quickly, and the beginnings of the eyes and ears are taking shape.

Your baby is about 1.6cm long – around the size of a raspberry.

Fingers and toes are starting to form, and your baby is making small movements, although it will be many weeks before you can feel them.

Your baby is about 2.3cm long, roughly the size of a grape.

The face is becoming more defined, with the eyelids and the tip of the nose forming. The heart now has its four chambers.

Your baby is about 3cm long – around the size of a strawberry.

The major organs are in place and will keep growing and maturing. From the end of this week your baby is known as a fetus.

Your baby is about 4cm long, roughly the size of a fig.

The bones are beginning to harden, the fingers and toes have separated, and your baby can open and close their hands.

Your baby is about 5.5cm long – around the size of a lime.

Your baby is fully formed and now needs to grow. The kidneys have started working, and on a scan you may see your baby stretching, kicking or hiccuping.

Your baby is about 7.5cm long, roughly the size of a lemon.

Tiny vocal cords are forming and the intestines are moving into place inside the tummy. Your baby’s fingerprints are also developing.

Your baby is about 8.5cm long – around the size of a peach.

Your baby can make facial expressions such as squinting and frowning, and a fine layer of hair called lanugo is starting to cover their skin.

Your baby is about 10cm long, roughly the size of an apple.

The skeleton continues to harden, and your baby can sense light through their closed eyelids. Their legs are now longer than their arms.

Your baby is about 11.5cm long – around the size of an avocado – and weighs roughly 100g.

The muscles in the face and back are getting stronger, and your baby’s movements are becoming more coordinated.

Your baby is about 13cm long, roughly the size of a pear.

A layer of fat is starting to form under the skin to help keep your baby warm after birth, and the umbilical cord is growing thicker and stronger.

Your baby is about 14cm long – around the size of a sweet potato.

Your baby can now hear sounds, including your heartbeat. You may begin to feel the first flutters of movement, especially if this isn’t your first pregnancy.

Your baby is about 15cm long from head to bottom, roughly the size of a mango.

A creamy coating called vernix is forming on the skin to protect it from the fluid around your baby.

Your baby is about 25cm long from head to heel – around the length of a banana – and weighs roughly 300g.

You are halfway through your pregnancy. Your baby is swallowing fluid, which helps the digestive system develop.

Your baby is about 27cm long, roughly the length of a large carrot.

Your baby’s movements are stronger now, and you may notice regular times of day when they are more active.

Your baby is about 28cm long and weighs roughly 430g – around the size of a papaya.

Eyebrows and eyelashes are growing, and the lips and features are more distinct, which is why 4D scans from this stage can show your baby’s face in detail.

Your baby is about 29cm long and weighs around 500g – roughly the size of a grapefruit.

The lungs are developing the tiny air sacs they will need for breathing, and your baby may respond to loud noises.

Your baby is about 30cm long and weighs around 600g – roughly the length of an ear of corn.

The inner ear is developed, so your baby may sense when you move or change position.

Your baby is about 34cm long and weighs around 660g – roughly the size of a cauliflower.

Your baby is gaining fat, and their skin is becoming smoother and less see-through.

Your baby is about 35cm long and weighs around 760g – roughly the size of a lettuce.

Your baby’s eyes are starting to open, and they are practising breathing movements.

Your baby is about 36cm long and weighs around 875g – roughly the size of a head of broccoli.

This is the start of your third trimester. Your baby has regular periods of sleep and wakefulness.

Your baby is about 37cm long and weighs around 1kg – roughly the size of an aubergine.

Your baby can blink, and their brain is growing rapidly.

Your baby is about 38cm long and weighs around 1.15kg – roughly the size of a butternut squash.

The muscles and lungs keep maturing, and your baby’s kicks and stretches may be stronger and easier to see from the outside.

Your baby is about 40cm long and weighs around 1.3kg – roughly the size of a cabbage.

The fine lanugo hair is starting to disappear, and your baby is building up fat stores.

Your baby is about 41cm long and weighs around 1.5kg – roughly the size of a coconut.

Your baby can turn their head from side to side, and all five senses are working.

Your baby is about 42cm long and weighs around 1.7kg – roughly the size of a squash.

Most babies are now lying head down, although there is still time for your baby to turn.

Your baby is about 44cm long and weighs around 1.9kg – roughly the size of a pineapple.

The bones are hardening, apart from the skull, which stays soft and flexible to make birth easier.

Your baby is about 45cm long and weighs around 2.1kg – roughly the size of a melon.

The central nervous system and lungs are maturing, getting ready for life outside the womb.

Your baby is about 46cm long and weighs around 2.4kg – roughly the size of a honeydew melon.

There is less room to move now, so you may feel more rolls and wriggles and fewer big kicks. Keep noting your baby’s usual pattern of movements.

Your baby is about 47cm long and weighs around 2.6kg – roughly the size of a large papaya.

Your baby may start to move down into your pelvis, ready for birth.

Your baby is about 49cm long and weighs around 2.9kg – roughly the size of a winter melon.

Your baby’s organs are ready to work on their own, and they are still putting on weight each day.

Your baby is about 50cm long and weighs around 3.1kg – roughly the size of a pumpkin.

Your baby is practising sucking and grasping, skills they will use as soon as they are born.

Your baby is about 51cm long and weighs around 3.3kg – roughly the size of a small watermelon.

Your baby is fully developed and could arrive at any time.

Your baby is about 51cm long and weighs around 3.5kg on average – roughly the size of a watermelon.

This is your due date week, although only a small number of babies arrive on the day itself. Your midwife will talk to you about what happens if your baby hasn’t arrived by 41 weeks.