Fetus Growth: What is Going On Inside?

Pregnancy is a fascinating time. You women have the opportunity to create a human being inside your body. In just 40 weeks, the fetus growth progresses from the size of the tip of a ballpoint pen to a full size baby.

Fetus Growth:  First Trimester

Weeks 1 and 2: This week, the sperm and the egg are trying to unite and become what will eventually be your child.

Week 3: The sperm and egg have finally united and joined DNA. Your fetus growth now is at the stage of what is called a blastocyst. That means an accumulation of about 100 cells. No body parts or organs have began forming at this point.

Week 4: Cells continue to accumulate and a face begins to develop.

Week 5: The umbilical cord forms and the organs begin to develop.

Week 6: The fetus growth has reached the stage of its first heartbeat!

Weeks 7 and 8: The organs continue to grow. Days 17-56 are the most vulnerable stage for fetus growth. The baby is most sensitive to outside factors that affect development at this time.

Week 9: The baby is now the size of a peanut and their organs are fully developed.

Week 10: The fetus finally looks like a baby rather than a clump of cells.

Weeks 11 and 12: The fetus growth has reached operation! The baby is fully formed and the organ systems are now working.

Fetus Growth: Second Trimester

Week 13: By now, the fetus has become either a girl or a boy and the gender may be determined by an ultrasound.

Week 14: The baby will begin to respond to outside stimuli. If the stomach is poked, the baby might move around to get away from it.

Week 15: Fetus hair called lanugo begins to grow all over the baby. They also begin sucking their thumb at this stage of fetus growth.

Week 16: You will begin to feel the baby moving around at this point.

Week 17: The fetus is now 4.5 inches long.

Weeks 18 and 19: Taste buds are now forming, the baby will be able to distinguish sweet tastes. Reflexes are also functional by this time.

Weeks 20 and 21: The fetus is now able to hear sound.

Weeks 22 and 23: The baby has now reached one pound!

Week 24: The  immune system is functional and is producing White Blood Cells to protect against disease and infection.

Week 25: The baby is still getting bigger and stronger each day! You will now be able to hear the baby’s heart beat through a stethoscope and if you put your ear to the belly.

Fetus Growth: Third Trimester

Week 26: The child’s hearing has now fully developed and the child is experiencing cycles of sleeping and waking.

Week 27: The baby now has the ability to cry.

Weeks 28 and 29: The baby weighs approximately 2.5 pounds now and can open his/her eyelids. Dreaming is now taking place.

Week 30: The fetus is now 17 inches long.

Week 31: The baby can now recognize familiar sounds such as its mother’s voice.

Weeks 32 and 33: Layers of fat and muscle are still continuing to get bigger and stronger. The baby is now practicing opening and closing its eyelids.

Week 34: The fetus growth has now reached the 5 pound mark!

Week 35: The baby’s lungs are now almost fully developed and ready for air.

Weeks 36 and 37: The fetus growth has reached the stage of getting ready for birth. This week, the baby will drop assuming a head down position.

Week 38: The white coat and baby hair will begin to disappear as it gets ready for birth. The baby is also now producing antibodies to prepare it for the outside world.

Weeks and 40: Fetus growth has reached an end. The baby is now ready to be born. It will still continue to grow in size and mind; however, its bodily development is complete.

What an exciting 9 months pregnancy is. A few simple cells grow and transform into a human being, a precious child. That child wills still continue to grow and develop even into adulthood.


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