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Iowa Pregnancy Support

Your Growing Baby

Find out what’s going on inside

10 Fingers, 10 Toes, and a Whole Lot More

Life starts way before a baby takes its first breath outside the womb. Right from the start, as a baby begins to grow inside of mom, this little life can become someone unique. Their value doesn’t just come from how they’ll look or what they’ll do. It’s about how every person has their own greatness and importance. Before babies are born, even while inside their mom’s belly, they start to feel emotions like happiness, sadness, and love. Even though they’re not out in the world yet, they can learn and grow because their brains and senses are developing. This time in their life is just as important for how they can make a big impact in our world, and hopefully for the better.

All of biology starts at the time of fertilization. Scientists and chemists confirm a stunning explosion of zinc fireworks occurs when a human egg is activated by a sperm.

How the Baby Develops

Before being born, a brand-new person gets 23 chromosomes from each parent. This makes them one of a kind, never to be exactly the same as anyone else. Weighing just 15 ten-millionths of a gram, the adventure of life starts!

Did you know? Ninety percent (90%) of a person’s development happens before they’re even born.

Fetal Development

Pregnancy Apps

Many apps help you track your baby’s progress and your pregnancy. Here are a few we suggest that can be used for free on both Apple and Android:

What to Expect logo
Baby Centre App
MYTH vs. REALITY
What to Expect logo

First Trimester (Weeks 1–13)

Week 1: Conception, the baby is smaller than a grain of sugar, but the instructions are present for all that this person will ever become.

Week 2: The baby attaches and burrows securely into the wall of the mother’s womb.

Week 3: The baby’s blood vessels and sex cells form. Foundations for the brain, spinal cord, and nervous system are laid. 

Week 4: The baby’s heart has begun to beat. Eyes, ears, and lungs begin to form.

Week 5: Tiny arms and legs begin to appear as well as the baby’s face.  The baby’s blood is now separate from the mother’s blood.

Week 6: Tiny fingers and toes develop. The baby’s brain is developed into three (3) parts emotion and language, hearing and seeing.

Week 7: Buds of the baby’s milk teeth appear. 99% of the muscles are present, and brain activity is detectable.

Week 8: The baby begins spontaneous movement and is now well proportioned, about the size of a thumb. Every organ is present but immature. The skull, elbows, and knees are forming.

Week 9: If prodded, hands and eyelids close. Genitalia becomes visible, indicating whether the baby is a boy or a girl. The muscular movement begins.

Week 10: The baby’s fingerprints begin to form.  Nerve and muscle connections have tripled. Eyelids fuse temporarily to protect the baby’s delicate developing eyes.

Week 11: The baby “practices” breathing and facial expressions, even smiling.  The baby can also urinate, and stomach muscles contract.

Week 12: The baby is now three (3) inches in length and weighs two (2) ounces with fine hair on the face. The baby can swallow, feel, and respond to skin stimulation.

Week 13: The baby is still about three (3) inches long, but now weighs about three (3) ounces. It’s moving a lot, but it’s too tiny for the mom to feel yet. Its facial features, including teeth, might start looking like the parents. Airways are developing and the baby’s body is sensitive to touch.

Second Trimester (Weeks 14–27)

Week 14: The baby’s heart is working hard, pumping lots of blood through its body every day. It’s also starting to form eyebrows, and its eyes are moving.

Week 15: The baby’s brain is growing a bunch of nerve cells fast. It’s developing taste buds. Soon, it’ll start another growth spurt at 25 weeks.

Week 16: Now the baby is about five (5) inches long and weighs around five (5) ounces. It’s active inside the mom’s belly, turning, kicking, and sometimes even somersaulting. The mom starts feeling these movements. The baby’s bones and tooth enamel are starting to form, and its heart is pumping a lot of blood every day. Invasive medical procedures cause stress on the baby.

Week 17: The baby’s outer layer of the brain is working. Waste called meconium is building up in the bowels. Eyes have moved to their final position with the back layers of the eyes having distinct parts. The ears are almost done shifting.

Weeks 18–19: The baby is still small, less than eight (8) inches long, but it can have dream-like sleep. It’s growing nostrils and tiny toenails.

Weeks 18–20: The baby’s ears are working, hearing the mom’s heartbeat and other sounds, like music. It can feel pain, and doctors have even done successful surgeries on babies at this age.

Week 21: Hair on the baby’s head begins to grow. A baby born prematurely at this age has a better than 50% chance of surviving.

Weeks 21–26: The baby’s brain cells are growing a lot. It can react to loud noises and might even suck its thumb. It’s practicing breathing by moving amniotic fluid into its developing lungs.

Weeks 27–32: The baby recognizes its mom’s voice and is using its senses. It can open and close its eyes and understand when it’s awake or asleep. It can also relate to the moods of the mother. Its skin is becoming smoother, and the baby can do somersaults by moving in a way that is similar to walking.

Third Trimester (Weeks 28–40+)

Weeks 33–37: The baby’s immune system is maturing to fight infections. It is gaining about half a pound every week and is getting ready for birth. Its head bones are soft to make it easier to pass through the birth canal.

Weeks 38+: While babies are born about nine (9) months after conception, the baby is now considered “full-term.” Breathing motions will sometimes cause the baby to get hiccups. Very soon the baby will announce its arrival, outside the womb! 

At Birth: The moment a baby is born it is capable of responding to the world around them. They can be startled by loud sounds and calmed by a caring embrace. They can focus at a close range and have a keen sense of smell. They can cry, though tears may not appear because of underdeveloped tear ducts.

Baby Centre App