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first stage
The germinal stage begins at conception when the sperm and egg cell unite in one of the two fallopian tubes. -
second stage
The fertilized egg, known as a zygote, then moves toward the uterus, a journey that can take up to a week to complete. Cell division begins approximately 24 to 36 hours after conception. -
third stage
the blastocyst arrives at the uterus and attached to the uterine wall, a process known as implantation. -
fourth stage
When implantation is successful, hormonal changes halt a woman’s normal menstrual cycle and cause a whole host of physical changes. For some women, activities they previously enjoyed such as smoking and drinking alcohol or coffee may become less enjoyable. -
fifth stage
The mass of cells is now known as and embryo. The beginning of the third week after conception marks the start of the embryonic period, a time when the mass of cells becomes distinct as a human. -
sixth stage
The embryo begins to divide into three layers each of which will become an important body system. Approximately 22 days after conception, the neural tube forms. This tube will later develop into the central nervous system including the spinal cord and brain. -
seventh stage
Around the fourth week, the head begins to form quickly followed by the eyes, nose, ears, and mouth. The cardiovascular system is where the earliest activity begins as the blood vessel that will become the heart start to pulse. -
eighth stage
During the fifth week, buds that will form the arms and legs appear. -
ninth stage
By the time the eighth week of development has been reached, the embryo has all of the basic organs and parts except those of the sex organs. It even has knees and elbows! At this point, the embryo weighs just one gram and is about one inch in length. -
Final stage
The early body systems and structures established in the embryonic stage continue to develop. The neural tube develops into the brain and spinal cord and neurons form. Sex organs begin to appear during the third month of gestation. During the period from seven months until birth, the fetus continues to develop, put on weight, and prepare for life outside the womb. The lungs begin to expand and contract, preparing the muscles for breathing.