1st Trimester

Week 1

Since your pregnancy is dated from the first day of your last period, you won't have even conceived yet!

Week 2

A new egg is released from the ovary and travels along the Fallopian tube,where it is fertilised by a single sperm. It divides immediately into a growing cluster of cells and makes its way towards the womb.

Week 3

The cells form a fluid-filled sphere with an inner layer that is your developing baby. An outer layer - the placenta and amniotic sac (the protective bag of water where baby floats) burrows into the soft lining of the womb, using fine hairs to anchor and absorb nourishment.

Week 4

The egg develops into an embryo the size of a grain. During this time, the inner cells form two and later, three layers that will become different parts of your developing baby's body: the brain, nervous system, skin, eyes and ears; lungs, stomach and gut; and heart, blood, muscles and bones.

Week 5

At only three weeks after conception the heart begins to form and the nervous system develops. The embryo forms into the shape of an elongated sea-horse, with head and tail ends.

Between Week 5 to Week 8 My UltraBaby's Early Pregnancy scan can be performed

Week 6

The embryo has a well-defined head and body, and is now visible to the naked eye. The brain is rapidly growing and there is a heart beat. 'Limb buds' indicate where the arms and legs are growing, and miniscule buds for milk teeth begin forming in the jaw.

Week 7

Your baby is now the size of a sunflower seed, with a head that seems too big for the body and bent over the chest. The facial features are in development: tiny lips, little nostrils, eyes beneath the skin and dimple ears. The major internal organs are in full development and the brain is primitive.

Week 8

The face is becoming recognisably human as the jaw, mouth, tongue, nose and eyelids form. Tiny fingers and webbed toes are appearing. There is movement, though you may not feel it yet. Your baby is roughly the size of a kidney bean.

Between Week 8 to Week 15 My UltraBaby's Dating scan can be performed

Week 9

Now known as a foetus, the back is straightening and the head is becoming more upright as the neck forms. The arms, legs, fingers and toes are all growing longer and the limbs are now able to move individually. The umbilical cord is connected to the navel, forming the lifeline between you.

Week 10

The ankles and wrists are clearly defined, eyelids are fused over the developing eyes. The brain continues to grow at a phenomenal rate of about 250,000 new neurons (nerve cells) per minute.

Week 11

The placenta will start working during this time, to transport fresh food and oxygen to feed the baby. The head still accounts for about half the total body length but is now held up away from the chest.

Between Week 11 to Week 13⁺⁶ My UltraBaby's Nuchal Translucency scan can be performed

2nd Trimester

Your baby is growing rapidly and maturing during the second trimester. You will be able to see your baby on a scan and feel those first fluttery movements.

Week 12

Your baby is fully formed, has doubled in size in the last three weeks and can stretch, roll, yawn, wriggle her fingers, drink the amniotic fluid and wee. The internal organs will continue to mature, genitals are forming.

Week 13

Your baby resembles a miniature human being and is about as heavy as a 50p coin. If your baby is a girl, nipples appear and her uterus, cervix and vagina form. If your baby is a boy, a penis forms. Even as early as 13 weeks, your baby may find and suck their thumb.

From Week 13 onwards My UltraBaby's Reassurance scan can be performed

Week 14

Eyebrows and lashes start to grow, eyes have moved from the sides to the front of the head, and the ears have moved up from neck to head. The intestines are developing folds to absorb nutrients.

Week 15

The heartbeat is strong and the body is growing fast to catch up with the now developed head. The eyes are still tightly closed beneath sealed eyelids.

Week 16

The bones are hardening and tiny nails appear. Blood vessels show through the translucent skin, which is now covered in fine, downy hair called Lanugos. By now, your baby weighs about the same as a small pot of yoghurt.

From Week 16 onwards My UltraBaby's 2D Gender scan can be performed

Week 17

With plenty of room to kick and roll around, your baby is very active. 'Brown fat' is starting to lay down around the kidneys, chest and the back of the neck, to help regulate the temperature in the first weeks after birth.

Week 18

Now the big forehead and eyes are sensitive to light. Hearing is sufficiently good for responding to loud noises and can now hear your heart beating. There is now movement, somersaults and the trying out different positions inside you.

Between Week 18 to Week 24 My UltraBaby's Anomaly scan can be performed

Week 19

Permanent teeth are forming buds behind the milk teeth buds in the jaw. Arms and legs are now in the same proportion that they will be at birth. As nerves and muscles develop, control is gained over movements such as bending the elbow or frown.

Week 20

The skin is starting to thicken into four layers and a creamy, moisturising substance called Vernix covers it. Current measurements approximately 25cm from top to bottom, and if you go for a scan this week you'll be able to see your baby for yourself.

Week 21

You are transferring antibodies from your blood to your baby, to protect from infection during the early months of life. Taste buds are forming on the tongue, and there is now the ability to absorb water and sugars from the amniotic fluid.

Week 22

Your baby can now look from side to side, hear loud music or shouting, and distinguish sweet tastes from bitter ones. If you feel acrobatics just as you're dropping off to sleep, it could be because you breathe more deeply when you are resting, with the result that the oxygen supply to your baby increases.

Between Week 22 to Week 34 My UltraBaby's 3D/4D scan can be performed

Week 23

Your baby now looks very much how he/she will look when born - although the skin is quite red and wrinkled, more fat stores will be laid down over the next few weeks.

Week 24

The vital organs are now mature except the lungs which are not ready to cope with independent breathing. So, if you went into labour now your baby would need special care. Any baby born at or after 24 weeks is considered 'viable' because it has a chance of surviving.

Between Week 24 to Week 34 My UltraBaby's Growth scan can be performed

Week 25

You can tell when your baby is asleep or awake, and may be able to feel a little hand or foot pressing against your tummy. Thumb sucking may now occur and has already developed a preference for using the right or left hand. It is possible for your baby to now even recognise your voice.

Week 26

The thickened skin, looks smoother and more opaque. The eyelashes have formed and your baby should be able to open it's eyes this week. Virtually all babies are born with blue or dark blue eyes and it's not until some weeks after birth that they become the colour they'll stay.

Week 27

Heart rate is around 120 to 160 beats per minute, roughly twice the speed of yours. There is a very good chance of surviving if born prematurely, although problems with breathing and keeping warm would mean special care is necessary.

3rd Trimester

In the final three months your baby will build up fat stores to provide energy for labour and help regulate body temperature after birth.

Week 28

The airways are developing and there is now regular movement. Babies kick most vigorously before week 30, this activity helps their muscles develop. After this time space becomes more restricted.

Week 29

The brain is bigger and amazingly complex, the lungs are still maturing in preparation for first breath as well as this the pupil iris is now able to dilate. You may notice that your baby becomes startled by loud noises.

Week 30

Those Braxton Hicks squeezes can probably be felt by your baby. They will not hurt, as the amniotic fluid cushions and protects. Your baby's body is about 33cm long from head to bottom.

Week 31

Still laying down fat stores, your baby will almost double in weight before birth. The creamy moisturiser and fine, downy body hair are beginning to disappear and the lungs are producing Surfactant, a substance that will help them to inflate more easily after birth.

Week 32

There is now rapid eye movements during sleep, just like you when you are dreaming. Your baby now measures around 40.5cm from head to bottom, if born now special care would be necessary.

Week 33

Your baby is now settling into the birth position and your midwife can tell you which way he/she is going to be born. Head downwards is the norm, some babies remain in a breech position and a few lie across the uterus.

Week 34

Fluid is passing through your baby's kidneys and is recycled back into the amniotic fluid. To harden bones your baby is drawing on your calcium reserves, it is therefore important for you to eat plenty of calcium-rich foods.

Week 35

There is now a rapid growth phase and may gain up to 227g (1/2lb) a week. Through the wall of your tummy the open eyes can differentiate between darkness and light.

Between Week 35 to Full term My UltraBaby's Presentation scan can be performed

Week 36

The hearing is increasingly acute, the nails are growing and your baby may be born with a full head of hair. The body weighs about 51/2lbs (2.5kg) and measures 46cm from head to bottom.

Week 37

Finger and toenails are now complete, which means that your baby is considered clinically mature, though weight will continue to be gained about 28g a day. If you're expecting a boy, his testicles will have descended from his abdomen into his scrotum.

Week 38

The movements are likely to be prods, knocks and shifts, and strong ones can take you by surprise when you're resting. The growth slows down in the last week or two a sign that your baby is ready to be born.

Week 39

Some of your antibodies are passing through the placenta into the bloodstream to boost the immune system for six months while it matures. The bowel contains Meconium - a sticky, tar-like substance that will be excreted as the first poo soon after birth.

Week 40

Plump, mature and finally ready for life outside your womb. Now roughly 51cm long, though of course newborn babies vary greatly in size and weight.