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Pregnancy

There are a number of things that must fall into place in order to have a baby. The creation of a human being requires the right environment, the right factors, the right timing, and a great deal of luck. The first step occurs when an egg cell from a woman unites with a sperm cell from a man to form an embryo the beginnings of a human being. This process is called conception. After conception comes the process of fertilization, which is the process in which sperm cells must be present in the woman's reproductive tract at the time the egg enters the fallopian tube. This can happen in several ways. If the woman has intercourse with a man during the week preceding ovulation, then he may deposit semen (a fluid containing sperm cells) into the woman's vagina. Some of the sperm can make their way through the cervix (the opening of the uterus, located at the end of the vagina), into the uterus, and on up into the fallopian tubes. There, one of them may meet with the egg as it travels down one of the tubes toward the uterus. Intercourse is not the only way to get sperm in position. Another way is for a doctor to place sperm cells directly into the woman's uterus at the right time in her cycle, a technique called intrauterine insemination. These sperm can also swim up the fallopian tubes, seeking the egg. Furthermore, when the sperm meets the egg, they attempt to penetrate the egg's outer layer. When one succeeds, the egg's outer surface forms a barrier to prevent other sperm from penetrating. The union of the sperm and egg is called fertilization. The fertilized egg is the first cell of a new human being. It contains a complete set of the genetic information necessary for the development of a baby. Half of that genetic material comes from the mother, carried in the egg; the other half comes from the father, carried in the sperm cell. That means the baby will have a combination of characteristics from both parents.
The next step after fertilization consists of the...

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