The terms fetus and baby are used for different stages of development of a child inside mother’s womb. The distinction between both is made by studying gestational age. Gestational period is the time during which a young one stays inside mother’s uterus. Human gestational period is of 9 months.

Fetus

A fetus is an unborn or un-hatched vertebrate that shows signs of a mature animal. It is called as an ’embryo’ in its early stages of development. A fetus is multi-cellular and takes its form due to the growth and development in an embryo. Fetus is ‘intra-uterine’.

Baby

A baby refers to a very young human, specially from the time of birth to a couple of years until it learns to walk on its own. Baby is an human offspring after it is delivered by the mother. So, it is ‘post-natal’.

Fetus Vs Baby

Terminology

The word ‘fetus’ is used in commonwealth nations. ‘Fetus’ is preferred by the scientific fraternity and is also used in North America. Other synonyms are ‘phoetus’ and ‘faetus’.

The term ‘baby’ is used in the same sense throughout the world. It refers to the young one of a human. Many other species have specific names for their babies, like ‘kittens’ for the young ones of cats, ‘puppies’ for the young ones of dogs, etc.

Stages

A human embryo goes through many stages after conception to become a fetus. Its developmental sequence is: molecules in reproductive system, gametes, zygotes, morulas, blastocysts and then fetus. It takes its form after the 8th week of gestation. Till the time an embryo becomes a fetus, the aim is multiplication of cells to take on different functions later. Fetus has developed brain, heart, lungs, internal organs and arms and legs in formation. Once the embryo becomes a fetus, the aim is to prep the fetus for life outside the mother’s womb.

A fetus comes into the outer world and is called a ‘baby’. It is called an ‘infant’ till the time it needs its mother’s feed for fulfilling necessary functions of body. It is called a ‘toddler’ when it learns to crawl.

Time line

The process of development begins from a single human cell. Day 1 of fertilization to 8th week is called as the embryonic period. 9th week to 40th week is called as the fetal period.

A new born baby is termed as ‘neonate’ till the time it is one month of age. It is clinically called as an ‘infant’ till one year of age. During 3-4 years of age, a baby is termed as ‘toddler’. After that the baby gets into his childhood stage.

Developmental changes

Many important changes happen in the fetal stage of an embryo. This happens during the second and third trimester of gestation. Fetus starts to mature into a baby. Development of veins and arteries happen at this stage. Fetus’ heartbeat should be monitored carefully during this stage. Gender determination can be done around 20the week of gestation as fetus’ genitals are formed and clear enough in the ultrasound.

During the early development stage, baby’s body and brain learn to adjust in the outside world. A baby may smile, raise it head and chest, track objects with eyes, open and shut its eyes, bring hands close to its mouth during the first three months of age. During 4-6 months baby tries to reach out further to understand the world better. It can roll over from one side to another, make babbling sounds, laugh and sit up with support from elders. During 7-9 months a baby tries to drag itself out of elders’ lap and crawl on hand and knees. It is able to produce monosyllabic sounds like ‘ma’ ‘pa’. During 10-12 months of development, a baby become a toddler and learns to feed itself. It can cruise inside the room holding onto the furniture.

Conclusion

Fetus and baby are just two milestones in the development of a cell. Fetus grows inside the mother’s uterus and a baby grows out in the real world. Both are prone to infections and should be taken proper care of. Both are in the best learning period of their lives. What do you say?