Weeks 1 and 2

• Development in the first two weeks is taking place at a microscopic cellular level.
• Fertilization of the ovum by the sperm occurs at conception.
• At fertilisation, all the hereditary characteristics are united into a single cell, called the zygote. This cell with its full complement of 46 chromosomes (half of each pair from each parent) now contains all the information necessary to guide the development of a new individual who will share the characteristics of both parents.
• The fertilised ovum implants into the lining of the mother’s uterus about 3 to 5 days after fertilisation.
• Cells called trophoblasts surround and nourish the embryonic cells (from which the baby develops).
• The trophoblastic cells eventually form the placenta and embryonic membranes which surround the baby.

Embryonic Period

Week 3

• During this period, all the major organs begin to be formed.
• You will excrete higher levels of pheromones at this time.
• Your progesterone levels will increase this week causing the lining of the uterus to build up.

Week 4

• The heart and the circulatory system are developing.
• The embryo now appears as a C-shape with the body flexed.
• Connecting stalk is formed. This will become the umbilical cord, connecting to the placenta.
• The cells on the outside of the C-shape form the spinal cord from which the brain, backbone and spinal cord and nerves will develop.
• Other cells develop into the major intestinal organs.

Week 5

• By the fifth week the embryo develops a human-like appearance and is approximately 1 to 2 cms in length, from head to toe.
• Head growth is rapid due to the rapid growth of the brain.
• Facial features are already forming.
• Major organs continue to grow.
• Your embryo’s heart is dividing into chambers and has already begun to pump blood.
• The arms and legs begin to develop, and the hands and feet are visible.

Week 6

• The head is rounded but still disproportionally large.
• The embryo’s facial features are forming with eyes, ears, nose and mouth recognisable.
• The arms and legs are even more noticeable now.
• The pituitary gland is developing. This gland will secrete essential hormones.
• The heart now has very distinct right and left chambers.

Week 7

• Little fingers and toes are more distinct, although they’re still webbed.
• The embryo is moving around a lot which can be seen on ultrasound but you won’t physically notice for another 11 to 14 weeks.
• The distinct areas of the brain are now visible.
• The embryo is now around two centimetres long, from head to toe.

Fetal Period

Week 8

• Your embryo is now officially called a foetus.
• All the organs, muscles, and nerves are beginning to function.
• The toes and fingers are beginning to lose their webbed appearance.
• Eyelids are beginning to develop but they are still fused.

Week 9

• All the joints are developing.
• The ankles have formed and the arms now bend at the elbows.
• The inner workings of the ears are complete.
• The genitals have begun to form but it’s still too early to tell the sex gender.
• Your foetus is now over four centimetres long, from head to toe.

Week 10

• Tiny fingernails and toenails have appeared.
• The liver, kidneys, intestines, brain, and lungs are fully formed.
• The head is now very large and is almost half the length of the entire body.
• The foetus is now over five centimetres in length.

Week 11

• All the parts of the baby are now formed, however, there’s a lot more development and growth left to happen.
• Tiny tooth buds are beginning to appear under the gums.
• Some of the baby’s bones are beginning to harden.
• Your foetus is now growing rapidly and is six to eight centimetres long.

Week 12

• The eyes have moved round from the side of the head to be closer together.
• The kidneys are producing urine.
• Small amounts of amniotic fluid are swallowed by the baby which aids foetal digestion.
• All structures in the full term baby are in existence at week 12.
• Nerve cells have been multiplying rapidly and the foetus has reflexes. For example, touching the eyelids would make the eye muscles clench.
• Your baby is now eight centimetres long.
• By week 12 the baby’s sex can sometimes be determined.

Week 13

• Baby’s heart-beat can be heard by using a Doppler amplifier device.
• Meconium (a thin, dark greeny black substance) begins to be present in the baby’s bowels.
• Fine downy hair begins to develop on baby’s skin.
• The skeleton and skeletal muscles now hold the baby more erect.
• Baby’s sucking and swallowing reflexes are now present.
• Arm and leg movements become stronger and some women may even experience them as fluttering movements at this stage!
• If you gently prod your stomach your baby will follow its instincts and start searching for a nipple to suck.
• The foetus is just over nine centimetres long.