Gestation is the period of time from fertilization to birth, when a human grows and develops in the uterus. It lasts about nine months.
After sperm fertilizes an egg, we now have the first cell of what can potentially develop into a brand new human.
The cell begins to divide. First it splits in half and becomes two cells. Then the two cells split in half and become four cells, and then the four cells divide into eight cells, and so forth.
About a week later...
If the egg and sperm joined together inside the human body, the ball of cells tumbles down the fallopian tube as it divides, and can attach to the inside of the uterus.
If the egg and sperm joined together outside the human body, a doctor transfers the ball of cells back to a human body, where it can attach to the inside of the uterus.
About eight weeks later...
Although the growing baby is only the size of a golf ball, all of the essential internal and external body parts are in place. For the next seven months, the body parts grow and develop, until the baby is born. Regardless of who, how, or why of how the sperm and egg got together, we all grew from one cell into a 75 trillion (that is the number 75 with 12 zeros) celled human.
It may have been your mom,parent, birth mother, first parent, traditional surrogate, or gestational surrogate that was pregnant with you.
A traditional surrogate is pregnant and gives birth to a baby who will be raised by someone else. It is the traditional surrogates eggs that are used for fertilization.
A gestational surrogate is also pregnant and gives birth to a baby who will be raised by someone else. However, it is not a gestational surrogate's eggs that are used. It could be eggs from your mom or a donor. The eggs were fertilized with your dad or donor sperm through IVF. The resulting ball of cells were put into the uterus of the gestational surrogate.
Sometimes we know about the person who was pregnant with us, and other times we don't.