1.

Ovulation

An egg is released from an ovary of a female.

2.

Copulation

Sperm from the male is released into the female's vagina during sexual intercourse.

3.

Fertilisation

The nuclei of the egg and sperm fuse , the fertilised egg is called a zygote.

4.

Cell division

$$24\ hours$$​ after fertilisation, the fertilised egg has divided into two. After four days it has divided into $$32$$​ cells, it is now an embryo.

5.

Implantation

One week after fertilisation, the embryo implants onto the uterus wall and the placenta begins to form.

Time

Description

​$$1\ month$$​​

The embryo is $$6\ mm$$​ long. It has a brain, heart, eyes, ears and legs.

​$$9\ weeks$$​​

The body is now $$25\ mm$$​ long and completely formed. It is now called a foetus.

​$$3\ months$$​​

The foetus is $$53\ mm$$​ long.

​$$5\ months$$​​

The foetus is now $$160\ mm$$​ long. It kicks and has fingernails.

​$$7\ months$$​​

The foetus is now $$370\ mm$$​ long and viable. This means it has a fair chance of surviving if it was born now.

​$$39\ weeks$$​​

The foetus is $$520\ mm$$​ long and fully developed. It is ready to be born.