Your baby's development progress. What to expect?

You will no doubt be curious about your baby’s development progress, especially if you are carrying your first child. For most women, regular antenatal check-ups will give you a sense of your baby’s development. But have you ever wondered what’s happening between those check-ups? Read on to find out more about the milestones in your baby’s development.

The first trimester

Week 1

The fertilised egg starts to divide as it travels along the Fallopian tube to your uterus

Week 2

After 6-7 days, the fertilised egg continues to divide and will form a hollow ball called a blastocyst. By day 10 it becomes embedded in the uterine wall

Week 4

Your baby is roughly 2mm (one sixteenth of an inch) in length. Its body tissues are beginning to form

Week 6

Your baby is about the size of your fingertip. The tiny heart has started to develop and function, and is beating 180 times a minute, which is more than twice as fast as yours. Eyelids, ears, the roof palate of the mouth, hands and feet are starting to form. Your baby’s head and spine are now discernible

Week 6

Now about 2.5cm (one inch) in length, your baby can start to move its body and legs. These movements can be picked up by a monitor, but you can’t feel them. By now the mouth is able to open and close. The lungs, liver and kidneys are forming.

Week 10

Your baby is not yet 4cm in length. The digestive system is developing. The nervous system and brain has matured enough for the baby to wriggle and move about. All the organs have been formed by now, and the baby is fully recognisable as a human being

Week 12

Your baby is fully formed, including the face. The liver starts to produce red blood cells and the kidneys are functional. The nails and hair are beginning to grow, its jaw has 32 tiny teeth buds, and it starts to suck. However, at just 6cm (2.5in) in length, there is still a lot of growth to occur. The head is growing to catch up with the growing brain, and internal sex organs are forming

Second trimester

Week 14

By now the placenta is doing all the work to maintain your pregnancy, supplying nutrients and oxygen. Your baby can respond to noise, light, and touch. Their arms and legs are fully formed.

Week 16

Your baby’s body is growing faster than the head, and their movements are more vigorous. The face is looking more human. The baby’s bones, consisting of soft cartilage up til now, will start to become stronger as minerals are deposited into the bones. Your baby’s brain is developing, increasing in size by 250,000 cells a minute!

Week 18

Your baby now measures about 18cm (7in) in length and weights about 170g (6 oz). The face can frown and squint. Eyelashes and eyebrows are developing. The baby also practices breathing, and can suck its thumb.

Week 20

Your baby is about half as long as it will be at birth. Their brain cells are continuing to multiply at a very high rate: 50,000-100,000 per minute. The spinal cord is thickening. Growth rate now starts to slow, allowing the body’s systems to mature.

Week 22

Your baby’s senses, including taste buds, are becoming fully formed. It can respond to sounds and voices. Playing music may even stimulate brain-cell activity

Week 24

All major organs are formed. Your baby’s heart rate has dropped substantially and can be recorded. Their eyes can open and close. The arms and legs are well developed – you will be able to identify the different parts of the baby’s body through your abdomen. The skin is translucent and the blood vessels underneath are clearly visible.

Week 26

Your baby will have established a sleeping and waking pattern by now.

Third trimester

Week 28

Another growth spurts begins, and your baby will start to put on more weight. Their eyes open at times and have the ability to focus. If born now your baby would have a good chance of survival under special care.

Week 30

Your baby is now about 34cm in length. Their lungs are almost fully developed, and have started to produce surfactant, which assists breathing. The baby will also have increased muscle tone, and can orientate itself in space. It will occasionally turn to a head-down position

Week 32

The skin is becoming pink as white fat are being laid down. These fat layers will help your baby regulate body temperature after birth, and also act as a source of energy. Fingernails, but not toenails, are fully grown. The face is predominantly smooth with some wrinkles.

Week 34

Your baby is nearly fully formed, and in the same proportion you would expect to see at birth. It is gaining weight, and their body systems are still maturing. The brain and nervous system are fully developed, but the immune system is still immature and continues to receive antibodies from you. It now measures about 37cm (15in) in length.

Week 36

The growing size of the baby means that there is less room to move about. Their brain uses about 70% of the oxygen and nutrients coming through the placenta. If the baby were born now, it probably would survive without too many problems because most of their organs are quite mature at this stage.

Week 38

Your baby is ready to be born! Remember, 40 weeks of pregnancy is calculated from the first day of your last menstrual period, whereas 38 weeks of pregnancy is calculated from the moment of conception. Your baby is plump and only just fits inside your uterus. Your baby’s head should now be pressed against the partially opened cervix and ready for delivery.