The zygote stage.
- At conception the zygote is formed. A zygote is a tiny bundle of cells. it keeps growing until implantation, when it attaches to the uterus lining.
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The embryo stage.
- From implantation until eight weeks the developing baby is called an embryo. This is the stage where everything in the body if formed. By week 4, arms and legs buds are present and the heart starts to beat. By week 6 arms are short, but fingers are developing. Both the heart and the liver can be seen. Between week 6 and week 8 the vertbrae, which protects the spinal cord, are forming and by week 8 the embyro becomes a foetus.
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The foetal stage.
- By week 8 the developing baby has everything that it will have when it is born. From now on it is growing and maturing. Muscles start to work and by week 12 arms and legs move constantly. Sex organs are well developed and soft nails and teeth are forming.
By week 20 the foetus can **** and grip. Ultrasound scans sometimes show the foetus gripping the umbilical cord. The foetus has been able to hear for a while now and makes strong movements that the mother can usally feel.
By week 22 the foetus is covered in a soft downy hair called lanugo.
By week 24 a protective creamy layer called vernix caseosa coats the skin and stops the skin drying out.
By 28 weeks the foetus is considered medically viable. By week 36 most infants are positoned for the birth with the head well down.
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