What Is The Difference Between An Embryo And A Foetus

What Is The Difference Between An Embryo And A Foetus

The gestation period consists of three main stages: the first refers to the zygote, the second to the embryonic period and the third to the foetal stage. There are many people who find it difficult to differentiate between them. People are often unsure when an embryo becomes a foetus. Therefore, in this OneHowTo article we answer this question and show you what they both are. Read on and discover what is the difference between an embryo and a foetus.


After 24 hours of the union between the egg and sperm, the second stage of gestation begins, called the embryonic stage. This is when the creation and development of the embryo occurs. This period was also characterized by passing through different stages until the end and give rise to the foetus.

During the first five days, the two cells that initiate the formation of the embryo start to divide and create more cells to the point of being unable to distinguish clearly. We now call this stage the embryo stage. After five days, is now called a blastocyst. At this stage of gestation the embryo is round and starts creating an internal cavity which will lead to the formation of the placenta and the rest of the body of the baby. The first days of the blastocyst are the most important because it is when you should look into the uterus of the mother and begin to see the process of pregnancy. Normally this process ends 14 days after fertilisation.

Once implemented, it will begin to grow and develop rapidly, so that it will acquire a similar elongated shape of a baby. From the eighth week of pregnancy onwards, the being already has all the organs and extremities in different stages of development. This is when the foetal stage starts and the embryo becomes a foetus.


As specified in the preceding paragraph, once it reaches week 8 of the gestation period, we're no longer talking about an embryo but rather a foetus, because the creature already has all the internal organs, although they're still not fully developed. The arms, legs and fingers start to take shape. From this moment on, the being will be considered a foetus until birth, so this is the longest stage of the pregnancy.

Differences between embryo and foetus

Once the definitions of both stages of pregnancy have been explained, it's easy. Here's the differences between embryo and foetus:

  • Embryo is the name given to the being from conception until the first 8 weeks of pregnancy.
  • From 8 weeks onwards until the day of birth it is a foetus, not an embryo.
  • The foetus has all its internal organs while the embryo is still developing them.
  • The foetus begins to form the limbs to acquire the entire shape of the baby.
  • The embryo has defined all parts of the body.

This article is merely informative, oneHOWTO does not have the authority to prescribe any medical treatments or create a diagnosis. We invite you to visit your doctor if you have any type of condition or pain.

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