Do you know? life inside the fetus starts with a single cell and it gradually multiplies and by the time the baby is born, there are 200 million cells. The total weight of these 200 million cells is 6 billion times the weight of the egg that was fertilized.

Embryo and fetus are the different stages of development of a body  Embryo is the first stage of the actual development of the organism but the Fetus stage follows the embryo stage in the development of the baby. Below in this article, we have neatly drawn the differences between the two confusing terms.

Stages of human embryo development

There are four stages of development of a body – zygote, embryo, fetus and finally a baby. The zygote is formed as soon as the sperm comes in contact with the egg and is fertilized. The zygote consists of 32 cells in all total.

The embryo is formed when the zygote cells begin to divide after 4 days to form new cells. It is called fetus when 9 weeks pass away since fertilization, and at this stage, the organs have already started to function. The baby continues to be called as a fetus until the stage child is born when we call it baby.

Embryo –  

Embryo marks the first stage of the actual development of the baby. In organisms that reproduce via sex, firstly a zygote is formed when sperms come in contact with the egg. This stage of initial cell formation is called zygote formation. After approximately 4 days this zygote cells split up to form an embryo. An embryo is the first thing that one sees when going through a pregnancy test. As time progresses, the embryo starts to develop tiny buds which later grow on to become the different parts of the body. This stage is very critical for a mother, and she should be extremely careful during this period. Most number of miscarriages takes place during this juncture only. Alcohol, cigarettes caffeine should be strictly avoided at this stage, and appropriate rest along with healthy diet is a must at this time for the healthy development of the baby.

Fetus –

The embryo starts to develop in the fetus from the ninth week after fertilization. At this stage, most of the body parts have already been formed such as lungs, liver, etc.fertilisation, and they have already started performing their respective functions by this time. External genitals too can be seen on Ultrasound screen. The baby continues to be called as a fetus until delivery when it is finally called a child.

Key Differences  between Embryo and Fetus–

Embryo Fetus
That stage of baby development when the zygote splits up into newer cells (usually after 4 days of fertilization) When embryo matures up it is called a fetus.
It is the second stage of baby development in the organisms which reproduce sexually. It marks the 3rd stage of baby development.
From the time of fertilization to 8th week of baby development is called embryo.( 1st to 8th week) From 9th week onwards  till the final delivery the developing child is called fetus (9th  to 36th week)
Buds which will later develop into body parts start to grow. Most of the body parts are already formed at the initial stage of the fetus, i.e. liver, kidney, etc.
The embryo is the most critical stage of pregnancy. The mother should be extremely careful and should not consume drugs, alcohol, nicotine, etc. at this period. Proper rest is also must. The physical symptoms ease up a little bit. However, for some women, it may remain as it is.
The most miscarriage takes place during this stage.  Comparatively, there is less number of miscarriages in this period.


Author’s Corner (Summary)-

The Embryo and the Fetus both mark the different stages of the development of the baby child. When the sperms get in contact with the egg, the zygote is formed which develops into embryo after 4 days. During this stage, the body starts to form buds which would later grow to become different organs by the end of this stage only.

The fetus, on the other hand, is the stage which occurs after 9th week from fertilization. At this stage, the body parts have are already formed, and one can see them working in the ultrasound screen. The baby till final delivery occurs, continues to be called as a fetus.




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