Stages of a Baby in the Womb

Updated April 17, 2017

From the minute that an egg is fertilised by a sperm, life is growing in the woman. The various stages of development are amazing as the baby grows quickly from nothing more than a blob of cells into a person.


Conception occurs when the sperm meets the egg after a woman has ovulated. The egg begins to divide quickly into a number of cells. At this stage the baby is called a zygote. Gradually the zygote travels through the Fallopian tube to the uterus where it will implant into the uterine wall.


The zygote begins a transformation period that is relatively brief. The cells divide and become a blastocyst. Eventually the blastocyst breaks in half, one part becomes the placenta and the other will become the foetus. Before it is a foetus it is an embryo.


At the close of four weeks, the embryo is still small, no bigger than an ant. The embryo resembles a tadpole because it still has a tail rather than legs. The major organs are starting to develop. During the next few weeks the embryo develops rapidly. The limbs begin to form, the eyelids and tongue develop, and the embryo has a fast paced heartbeat.


By the end of the eighth week the embryo advances to become a foetus. It now has a head, arms and legs that only need to grow. Now the growth of the baby is broken up into trimesters. By the completion of the first trimester a heartbeat can be detected on a Doppler, a device that doctors use to detect faint heartbeats.

Second Trimester

During the beginning of the second trimester the foetus can hear outside voices. The foetus is developing muscles and can swallow and suck. All of the major organs have developed and the size of the foetus is about 7 inches long, according to MSN Health & Fitness. During the fifth month of fetal development the mother usually begins to feel the baby moving inside of her. Hair begins to develop on this 1 pound foetus. By the end of this trimester the face of the foetus is recognisable and can weigh about 0.907 Kilogram.

Third Trimester

The beginning of the third and final trimester marks the foetus having full hearing and the ability to taste. The middle of this trimester the foetus is not quite as active because the space inside of the mother is not as ample. The last month is when the foetus just grows and develops some layers of fat so that it can stay warm. The average foetus weighs 7 or 8 pounds by this point and is usually about 20 inches long, according to MSN Fitness & Health.

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About the Author

Cheryl Hinneburg has been a freelance writer for five years. In addition to the regular clients that she works for, Hinneburg also writes regularly for Demand Studios and Associated Content, and is a provider for eLance. She is an award-winning poet and is currently working on a Master of Science with a certificate in substance abuse counseling at Capella University.