Fetus facts for kids
A fetus is a stage of development for many animals, including humans, before they are born. It's like a tiny, growing creature inside its mother. In humans, the fetal stage begins about 8 weeks after a fertilized egg starts to develop. This stage lasts until the baby is born. During this time, the fetus grows rapidly and its body parts become more developed.
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What is a Fetus?
A fetus is the name given to a developing organism after it has passed the earliest stage, called the embryonic stage. For humans, the embryonic stage is the first 8 weeks after the egg is fertilized. After 8 weeks, the developing human is called a fetus. This is when many of the major body parts have started to form, and they will continue to grow and mature until birth.
How a Human Fetus Develops
The journey from a tiny fertilized egg to a baby ready for birth is amazing! Here's a simple look at how a human fetus develops:
Early Fetal Growth
- Weeks 9-12: At this point, the fetus is about the size of a plum. Its face starts to look more human, and tiny fingers and toes are fully formed. The heart beats strongly, and the fetus can even make small movements, though the mother usually can't feel them yet.
- Weeks 13-16: The fetus grows quickly, reaching about 4-5 inches long. Its skin is thin, and you can see blood vessels through it. Hair might start to grow on its head, and it can even suck its thumb!
- Weeks 17-20: By this time, the fetus is about 6 inches long. The mother can often feel the fetus moving, which feels like gentle flutters or kicks. The fetus's senses are developing, and it might react to loud noises.
Later Fetal Development
- Weeks 21-24: The fetus continues to gain weight and grow longer. Its lungs are developing, but they aren't ready to breathe air yet. The fetus starts to develop sleep and wake cycles.
- Weeks 25-28: The fetus is getting much bigger and stronger. Its brain is growing rapidly, and it can open its eyes. If born at this stage, a baby would need a lot of medical help to survive.
- Weeks 29-36: The fetus gains a lot of weight, getting ready for birth. Its bones are hardening, and its lungs are maturing. It usually turns head-down, getting into the best position for delivery.
- Weeks 37-40: By now, the fetus is considered full-term. It's ready to be born! All its organs are fully developed and ready to work outside the mother's body.
Fetal Life Cycle in Other Animals
Just like humans, many other animals also have a fetal stage. For example, elephants have a very long fetal stage, lasting almost two years! Whales and dolphins also develop as fetuses inside their mothers before they are born alive into the water. The length of the fetal stage depends on the animal and how long it takes for them to develop fully before birth.
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