Preborn Development

This section shows the journey through the first chapter of human life.

During the short nine months from conception to birth, a microscopic single cell evolves with amazing speed into (on average) a seven-pound, 20-inch, fully-formed infant.

Not long ago, the first nine months of human life were a mystery to all, only in recent years have scientific and technological advances allowed us to observe life directly as it develops in the womb. We now know in great detail how a baby grows...

1st trimester- Weeks 1-12

Weeks 1-5

Day 1

Sperm joins with ovum (egg) to form one cell- smaller than a grain of salt- called a zygote. This one cell contains the complex genetic blueprint for every detail of human development- the child’s sex, hair and eye colour, height, skin tone.

Days 3-4

The fertilised egg continuously divides as it travels down the fallopian tube into the uterus, where the lining has been prepared for implantation.

Days 5-9

During this time, the fertilised egg implants in the rich lining of the uterus and begins to draw nourishment. The embryo is no bigger than a full stop.

Days 10-14

The developing embryo signals its presence through the placental chemicals and hormones, preventing the mother from menstruating. The missed period is usually the first sign that the mother is pregnant. By the second week the baby has developed from a hollow ball of cells called a blastocyst, into a flat disc shape (embryonic disc).

Day 20

Foundations of the brain, spinal cord and nervous system are already established.

Day 21

The baby’s head is developing and by day 21 the heart begins to beat. Primitive blood cells start to circulate the blood vessels.

Day 28

The backbone and muscles are forming. Arms, legs, eyes and eyes have begun to show. At 1 month old the embryo is 10,000 times larger than the original fertilised egg and is developing rapidly. The heart is now pumping increasing quantities of blood through the circulatory system.

Day 30

The placenta forms a unique barrier that keeps the mother’s blood separate while allowing nutrients and oxygen to pass through to the embryo; this exchange system also allows the disposal of waste from the embryo.

Day 35

Five fingers can be discerned in the hand. The eyes darken as pigment is produced.

Day 40

The head is the most prominent feature. It contains the growing brain-waves produced by the baby and can be registered on a normal brain-wave monitor.

Week 6

The heart is the size of a poppy seed and the digestive tract begins to form. The lungs, liver, pancreas and thyroid are all present. Facial features are starting to form and the nostrils are becoming distinct.

Week 7

At seven weeks the baby has its own fingerprints that carry the proof of its identity. The outer ear is present, and the inner ear, with its hearing and balancing mechanisms, is well established. The brain has divided into distinct segments and the cerebral hemispheres are growing fast. The heart is now becoming a four chambered organ and is beating at 150 beats a minute. The internal sex organs are now nearing completion.

Week 8

The embryo begins to move spontaneously. The jaw forms, including teeth buds in the gums. The baby’s skeleton begins to turn cartilage to bone. The tongue is present in the mouth and the eyelids are now discernible. The arms and legs are longer now and the hands can bend at the wrist. The baby can respond to touch by reflex and the vertebrae in the neck can bend.

Week 9

Soon the eyelids will seal to protect the embryo’s developing light-sensitive eyes, and will reopen at about the seventh month. At a little more than an inch long, the developing life is now called a foetus- Latin for ‘young one’. The baby has touch pads on its fingers and the jaw is now completely formed.

Week 10

The baby gets its food from the mother through the placenta. The baby has its own blood and never mixes with the blood of the mother because sometimes they are different blood groups. The baby’s nervous system is responsive and many of the internal organs are functioning. The kidneys are now moving into their final position in the upper abdomen.

Week 12

The baby is perfectly formed and can raise its eyebrows, wrinkle its forehead. By now the baby can yawn and suck, its hair and nails continue to grow and the bones are hardened due to the laying down of calcium. An expert would be able to see what gender the baby is on a scan. Vocal chords are forming and the pituitary gland is beginning to make hormones. The digestive system can now produce the contractions needed to push food through the bowels. The baby will move a lot during this time and will stretch its arms and legs and jump about.

Second trimester- weeks 13-24

Week 16- 4 months

By week 16 (4 months) the baby is a little over a third its birth weight. The mother begins to feel the first kicks and jumps. The baby can co-ordinate its movement and it is very active. Sometime the baby will hiccup and has a range of facial expressions.

Week 20 - 5 months

The baby sucks its thumb peacefully. By 5 months the mother is beginning to look pregnant. If the baby is female her own uterus is formed and her ovaries contain eggs. Vernix caeosa a thick greasy covering is protecting the skin and acts as a waterproof barrier. The skin now has four layers.

Week 24 – 6 months

The baby’s hearing is very well established now and likes to hear mothers voice and heartbeat. Rapid eye movements can be noticed.

Third trimester – weeks 25 - 40

During this last stage the baby puts on weight and perfects behaviours such as yawing, swallowing and grasping. Typically the baby is now head down in the mother’s pelvis awaiting birth. Birth usually comes at around 40 weeks. When the baby is born it has been alive for 9 months. What changes at birth is its environment and location, not his status as a human being.