There are a number of stages of development during pregnancy . This process starts as soon as five minutes after fertilization and remains so in the life of a child after its birth . Each stage moves to a human of an organism from a single initial cell to be able to survive outside the womb fully developed. Each stage of development is fundamental to the whole process of birth and, at least during the early stages, can not take place outside the body of a human female.
During the menstrual cycle, an egg is released from one ovary in a process called ovulation. He moved to the end of a fallopian tube and waits for fertilization. During this period, the sperm can travel from the vagina, through the cervix and into the uterus, where it can penetrate the egg. The sperm and egg combination is called a zygote.
The zygote enters the uterus after a few days and begins to go through the process of cell division. A placenta develops, and adheres to the wall of the uterus. The zygote is now called the blastocyst and begins to develop membranes, forming the amniotic sac within about 10 days.
After three weeks, organs and begin developing blastocyst into an embryo. This is the stage in which the overall shape of a baby develops. The heart and blood vessels begin to develop around day 20.
By the 12th week of pregnancy, the embryo becomes a fetus and fills the uterus. Soon after, the sex of the fetus can be identified. At 20 weeks, the fetus begins to move in a way that women can feel.
At week 24, the fetus is able to survive outside the uterus and lungs and brain functions begin to develop. After birth at about 36 weeks, the brain continues to develop well into the first year of child’s life.