Stages of fetal development includes the process of development of a baby from fertilization till delivery. There are three main stages of fetal development: The Germinal Stage, The Embryonic Period and The Fetal Period.

Stages Of Fetal Development

Source: http://maternalfetalhealth.wordpress.com/2010/10/18/month-by-month-fetal-development/

Main Stages of Fetal Development

The Germinal Stage

Germinal stage is the stage immediately after conception. It lasts for first two weeks. Conception occurs when a male sperm fertilises with a female ovum. The fertilisation usually takes place in the fallopian tube. Zygote is the product of fertilisation. The zygote reaches the uterus within a week. The zygote undergoes cell division to finally form the fetus. The cell division starts within 24 to 36 hours. The zygote divid into two cells, thereafter it forms four cells. The process continues.

The outer cell walls will form into placenta and the inner cell walls, the embryo. The cells of the zygote divides rapidly to form the blastocyst. The blastocyst has three layers. The Ectoderm which later forms into skin and nervous system; The Endoderm which forms into the digestive and respiratory system; The Mesoderm which forms into the muscles and the skeletal system.

The blastocyst reaches the uterus and attaches itself into the walls of the uterus through implantation. There is rupture of tiny blood vessels of the uterine wall and a connection is made between the blood vessels. This provides nourishment to the growing embryo. After a successful implantation, hormonal changes occurs in the mother’s body. This stops the menstrual cycle and also guides the further stages of fetal development.

The Embryonic Stage

The blastocysts has now developed into an embryo The embryonic period starts from the third week of gestation and lasts till the eigth week. During this period the cells begin to form into a human. The neural tube formation is a very important development of this stage. It occurs after 22 weeks of pregnacy.

Stages Of Fetal Development

Source: http://embryology.med.unsw.edu.au/Lectures/BGDface/BGDface.htm

The neural tube is very important as it later develops into the brain, spinal cord and other components of the central nervous system. The head forms in the fourth week followed by eyes, nose, ears and mouth. The heart begin to show pulsations from fourth week, but the heart is not fully formed, it is merely blood vessels, and the lungs are formed in the eighth week.

The leg buds appear and the arms form as paddles in the fifth month. By the eighth week of fetal development almost all the organs except the sex organs have formed. The weight of the embryo reaches 1 gram and is 1 inch in length.

The Fetal Stage

The fetal stage of development starts from the ninth week and lasts till birth. The organs continue to grow. The neural tube differentiate into brain, spinal cord and the nerves. The sex organs develop by the third week. The fetus continues to grow in length and weight. The majority of development ocurs during the later stages of pregnancy.

The size of the fetus develops. The heart matures and the heart beat gets stronger. Fingernails, hair, eyelashes and toenails form. The brain and spinal cord becomes much mature too and begins to show some activity. The development of the fetus continues itself till birth.