Stages of Pregnancy

A single sperm penetrates the mother’s egg, this cell is called a zygote.As it travels down the Fallopian tube the zygote divides to form a ball of cells.When it has formed a group of inner cells with an outer shell it is called a “blastocyst”.The inner cells eventually become the embryo while the outer group of cells become the membranes that nourish and protect it.

By the 6th day the blastocyst implants into the uterine wall and sticks here tightly, by this time the lining of the uterus has grown and is ready to provide nourishment via the mother’s blood stream. It puts down tiny roots which eventually become the placenta.

By the 21st day, the neural plate begins to form into the neural tube, which will eventually develop into the spinal cord.

Tiny blood vessels begin to form and the heart starts to develop.

The amniotic sac is formed. The neural tube should close by the end of week 4, if it does not close properly spinal cord defects occur. By the 5th week the main parts of the brain; the forebrain, midbrain and hindbrain, develop further. Arm and leg buds are visible.

The fetus reaches a length of about 3.2 inches. Eyes are formed but not ‘connected’ by the visual cortex. The first synapses start to form in the brain. The head is now half the size of the fetus. The fetus can make a fist with its fingers. ‘Deliberate’ motion starts.

The fetus reaches a length of about 8 inches. The ears are fully formed; ‘hearing’ is possible. Lanugo covers the entire body. The fetus responds to touch around week 22. A waxy substance ‘vernix’ is covering its skin to stop it getting waterlogged by amniotic fluid. The mother can usually feel the fetus move.

The fetus reaches a length of 11.2 inches. Eye components are well developed. The myelination process begins; this means that the axons (the ‘wires’ that connect the brain cells) gain their fatty protective covering.