Beginning the moment that a sperm fertilizes an egg, a baby begins to grow in the womb. As it goes through the various stages of development, it grows from being nothing more than tiny cells into a baby that will hopefully be loved and cherished.
Zygote
The first stage of a baby occurs at conception. Once fertilized, the egg will begin to quickly divide into several cells. The baby is called a zygote during this stage. The zygote will gradually travel through the fallopian tube and into the uterus. Once in the uterus, the zygote will implant itself into the uterine wall.
Blastocyst
The zygote represents a brief period of transformation during which the cells will divide and eventually become a blastocyst. According to the Mayo Clinic, the blastocyst breaks in half with one part becoming the fetus and the other part becoming the placenta.
Embryo
At around the fourth week of pregnancy, the embryo is no bigger than an ant. At this stage, the embryo has a tail instead of legs and thus resembles a tadpole. The baby's major organs are beginning to develop. Over the next few weeks, the embryo begins to develop rapidly. The eyelids and tongue begin to develop, the limbs start to form and the embryo has a heartbeat that is fast paced.
Fetus
By the time the eighth week of pregnancy is complete, the embryo has become a fetus. It now has a head, legs and arms. Going forward, the baby's growth is broken up into trimesters. Once the first trimester is complete, a Doppler device can be used the detect the heartbeat.
Second Trimester
At the start of the second trimester, the fetus can hear voices outside the womb. The fetus can now suck and swallow and is beginning to develop muscles. The fetus is now about 7-inches long and all of the major organs are developed. During the fifth month, the mother should start to feel the baby move inside of her. The fetus will weigh around 1 pound and hair will be developing. By the time the second trimester ends, the face will be recognizable and will weigh around 2 pounds.
Third Trimester
The third trimester is the final stage in the development in the baby. At the beginning of the third trimester, the baby will have the ability to taste and has full hearing ability. Around the middle of the third trimester, the fetus does not move around as much due to the space inside the womb becoming smaller and smaller as he grows. During the final month of pregnancy, the baby develops layers of fat so he can stay warm after birth. According to the Medline Plus, a website of the National Institutes of Health, the average fetus weighs in at around s7 or 8 pounds and is about 20 inches long. This trimester ends with the birth of the baby.
