Brave new world: First year - text only -

• Conception
When a sperm penetrates the outer covering of the ovum, it travels through the cytoplasm and fuses with the nucleus of the cell, forming a zygote. This is the moment of fertilisation. During the days after fertilisation, the zygote divides into two cells, then four, and so on, until it becomes a ball of cells: an embryo. It then travels along the fallopian tubes to the uterus (womb) where it sinks into the lining of the uterus wall. This is were it will grow.

• Month 1
A dark mark appears on the embryo, indicating the position of a spinal cord.

A rudimentary heart develops and begins to beat. All the major organs begin to develop as early as the third week of pregnancy.

• Month 2
The body begins to elongate, though the head remains disproportionately large.

The face begins to develop: eyes are pigmented; nostrils, lips and ears, as well as fingers and toes, become visible.

• Month 3
At this point, the embryo becomes known as a foetus. During the third month, the foetus more than triples in length, while its weight increases by 16 times. Movement begins: the foetus can turn its head, purse its lips and hiccup.

Tooth buds appear in the jaw, and a definite chin, nose and forehead develop. The ears, which have appeared as gill-like growths on the neck, move up the side of the head.

A more baby-like body structure develops: the trunk of the body straightens, and ribs and bone tissue appear, though in the form of flexible cartilage. External sex organs start to grow.

• Month 4
The foetus's senses begin to develop. Although its eyelids are formed fused shut, it is nonetheless sensitive to light. It also begins to hear sounds.

The foetus swallows amniotic fluid and excretes it as urine. It receives oxygen from the placenta.

Fat begins to develop, allowing the foetus to conserve heat. Eyebrows also start to grow, and the fine hair on the head starts to coarsen.

• Month 5
Sensory development continues apace. The foetus can now distinguish between sweet and bitter, it is sensitive to touch and its hearing becomes more acute.

Fat deposits build up, and sebaceous glands produce a waxy substance to protect the skin and keep it supple.

Crucially, the foetus develops its own, very primitive immune system. A sheath forms around the nerves in the spinal cord to protect it.

The sex organs develop: the male scrotum becomes solid, while the female foetus's ovaries already contain ova in preparation for the day when she will become sexually active.

• Month 6
The head of the foetus is now growing more slowly than its body, redressing the balance. The body's shape becomes increasingly childlike, with bone beginning to harden and muscles developing in the arms and legs. Muscles allow the foetus to make breathing motions.

The brain cells used for conscious thought begin to mature. The brainwave patterns of a six-month-old foetus resemble those of a newborn. The foetus can distinguish its parents' voices and respond to music.

• Month 7
Nerve circuits within the brain are now fully active and the nerve fibres are encased in a fatty sheath for protection.

Fat builds up under the skin, smoothing out the wrinkles and making the foetus appear plumper. It is beginning to fill the amniotic sac, inside the uterus, and its movement becomes restricted.

Special cells line the surface of the lungs. These secrete a surfactant — a substance that reduces surface tension — which ensures they will not collapse when the newborn begins to use them. The bone marrow produces red blood cells.

The eyelids open, and the foetus can practise seeing and focusing.

A baby born at the end of the seven-month period (around 28 weeks) usually has a good chance of surviving.

• Month 8
The internal organs are almost fully developed. The face is also fully human: the irises can contract and dilate; the eyes can blink and focus.

Many foetuses 'engage' — turn their heads downwards in anticipation of delivery — at this point, though others may do it later.

• Month 9
The foetus sheds the fine hair that covers its body. This, along with pigment, secretions from the alimentary glands and cells from the bowel walls form a substance called meconium. Meconium fills the intestine, and will be the first substance that the baby excretes, either during or after birth.

Last-minute preparations for breathing are made: cortisone, a hormone, is produced to help the lungs to mature.

• Birth to 1 month old
The rate at which babies develop varies enormously, but there are certain benchmarks that most reach within the first 12 months of their lives.

As the first month progresses, they become increasingly alert. They move around more, making jerky movements with their arms. Although their vision is still very poor, they will watch you when you are close by and listen to sounds.

• 1–3 months old
Babies become alert and responsive. They may start to smile: a reflex action that they will continue to perform because it produces parental attention. They will begin to reach, grasp and kick and can follow a moving object with their eyes.

• 4–7 months old
Vision, touch and hearing become co-ordinated. Motor skills improve. By seven months, most babies can sit up and roll over. They begin to babble and enjoy social interaction. They can respond to their names.

• 8–12 months old
Babies become increasingly mobile. Most will crawl and a few will walk, usually while holding on to something. Babies begin to explore the uses of objects: shaking, banging and dropping them to see what happens. They may begin to use objects properly — drinking from a cup, for example. They begin to respond to verbal commands, such as 'yes' and 'no', and may begin to say words such as 'mamma'.

Sight and speech | Primative brain | First year

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