Your Baby’s Development Through Pregnancy

When we made plans well over a year ago for my niece and her husband to visit and go to the Alabama/Penn State football game, we had no idea she would be 23 weeks pregnant by kickoff. As we entered that deafening stadium of 107,000 roaring fans, I wondered what my grand-niece could be experiencing inside my niece’s tummy! How do babies develop?

Development Milestones of Pregnancy

Week 5:

• The brain, spinal cord, heart, and gastrointestinal tract begin to develop.

Weeks 6 to 7:

• Arm and leg buds are seen.
• Brain development begins, some cranial nerves are seen.
• Eyes and ears begin to form.
• Tissue that develops into the vertebra and some other bones is present.
• Heart continues to develop and beats at a regular rhythm.

Week 8 - About the Size of a Kidney Bean:

• Arms and legs are longer, foot and hand areas can be seen with webbed fingers and toes.
• Brain formation continues.
• Lungs formation begins.

Week 9:

• Formation of all essential organs has begun.

Week 10:

• The eyelids and ears become more developed.
• Facial features are developing.

Weeks 11 to 14 - About 3 Inches Long and 1 Ounce:

• Eyelids close until about the 28th week.
• Facial formation is advanced.
• Limbs are long and thin.
• Genitals are well differentiated.
• The head is large–about half the size of the fetus.
• Tooth buds are present.

Weeks 15 to 18 – About 5 Inches Long and 5 Ounces:

• The skin is mostly transparent.
• Fine hair develops on the head.
• Muscle tissue and bones develop, the bones become harder.
• There are active fetal movements.
• Sucking motions are made.

Weeks 19 to 21:

• The fetus can hear.
• There are more movements that the mother may feel as a fluttering.

Week 22 – Over 10 inches Long:

• Fine hair covers entire body and eyebrows and lashes are present.
• Nails are seen on the fingers and toes.
• The fetus is more active and the mother can feel the fetus moving.

Weeks 23 to 25:

• The lower airways of the fetal lungs begin to develop.
• Fat storage begins.

Week 26 – About a Pound and a Half:

• Eyebrows, eyelashes, and all parts of the eye are complete.
• A hand and startle reflex is present.
• Footprints and fingerprints are forming.
• Air sacs form in lungs.

Weeks 27 to 30:

• There is rapid brain development.
• The nervous system develops and can control some body functions.
• Eyes now open and close.
• The respiratory system can exchange some gas.

Weeks 31 to 34 – Over 15 Inches Long and About 3 Pounds:

• Body fat rapidly increases.
• Rhythmic breathing movements occur, but the lungs are not fully mature.
• Development of the bones is complete.

Week 38 –Over 19 Inches Long and Nearly 7 Pounds:

• The fine hair begins to disappear.
• Body fat increases more.
• Fingernails are seen at the ends of the fingertips.

Weeks 39 to 42:

• The fine body hair is gone except for on the upper arms and shoulders.
• Fingernails are seen beyond the fingertips.
• Small breast buds are present.
• Head hair is coarser and thicker.

“Roll Tide” Baby

So now I know that my 23 week grand-niece could hear all the noise surrounding us that day–although she was very safe and protected in her little world. I’m sure her first words will be “Roll Tide,” in honor of the University of Alabama’s varsity football team, the Crimson Tide!

If you are pregnant, you too can follow the development of your baby from early pregnancy through delivery. Awareness of these development milestones help you know your baby is progressing appropriately at each point in the pregnancy. Ask your health care provider to point out important stages at each prenatal visit.