Fetal Development

The Baby Inside of You:
This is information on the weekly development of your baby during the 40 weeks of pregnancy beginning from the 5th week. Just scroll down to see information about the week of pregnancy you are currently in.

Week 5
The ball of cells that is the sperm and egg joined is now called an embryo. The embryo is the size of an apple seed. The placenta and umbilical cord are already working to give nourishment to the embryo.

Week 6
The embryo heart has begun to beat. The embryo is about a quarter inch long. It has organs including kidneys and a liver.

Week 7
The embryo is now about a quarter inch long. There are dark spots for eyes and nostrils. There are small buds for arms and legs. The heart is beating about 150 times a minute.

Week 8
The embryo is about the size of a grape. It has slightly webbed fingers and toes. The baby's veins are visible through it's thin skin.

Week 9
The embryo is now called a fetus. It is constantly moving although you can not feel it yet. The hands and feet look like paddles because of the webbed fingers and toes.

Week 10
The fingers and toes of the fetus are clearly visible. The eyelids have fused shut and won't open again until week 27! The placenta has developed enough to supply the hormones.

Week 11
The fetus is now about two inches long. It has begun swallowing and kicking. The vital organs have formed.

Week 12
The fetus has toothbuds and toenails. The fingers and toes have separated and some bones have begun to harden.

Week 13
Your baby's face is beginning to look more human. It is 3 inches long. The ears are in the correct position and the eyes have moved from the side of the head to the front.

Week 14
Welcome to the second trimester! Your baby is now 3-4 inches long and already has it's own unique fingerprints.

Week 15
Your baby is covered with a thick downy hair that usually disappears before birth. It's eyebrows have begun to grow, and so has the hair on it's head. The baby can grasp, squint, frown, and grimace. It might even suck it's thumb!

Week 16
Your baby is probably hiccupping although you probably can't feel it. It is 4.5 inches, crown to rump.

Week 17
Your baby is now 5 inches long. It is breathing amniotic fluid.

Week 18
Your baby is now 5.5 inches long and weighs approximately 7 ounces. It's skeleton is made of a rubbery cartilage which will later harden into bone.

Week 19
This is a good time to have and ultrasound. During the exam your baby might kick, roll, or suck it's thumb.

Week 20
Your pregnancy is halfway over. The nerve cells for each of the five senses are developing in the brain.

Week 21
Your baby is steadily gaining fat to stay warm after it is born.

Week 22
Your baby weighs 3/4 of a pound and is 7.5 inches long. It can hear sounds from outside the uterus. It fingernails have reached the tips of his fingers. It eyelids and eyebrows are fully formed!

Week 23
Your baby now weighs a pound and is 8 inches long. It is proportioned like a newborn.

Week 24
Your baby now weighs a little over a pound. It's lungs are getting ready by developing blood vessels.

Week 25
It's skin is thin and fragile. Taste buds are now forming and your baby can even tastes sweets.

Week 26
Your baby will respond to touch. Also, if you shine a light on you tummy it will turn his head away.

Week 27
Your baby now weighs a little over 2 pounds and is 11 inches long. It's eyes are beginning to open.

Week 28
Welcome to the third trimester! Your baby now weighs between 2.5 and 3 pounds. He or she is between 12 and 15 inches long. It can now open and close it's eyes. Your baby's lungs are now capable of functioning with some help in the event of a premature birth.

Week 29
Starting about now your baby will turn his head towards sources of continuous bright light. It is putting on fat layers to get ready for life outside the womb.

Week 30
Your baby now weighs at least 3 pounds and could be almost 17 inches long. The brain is growing rapidly.

Week 31
Your baby lungs and digestive tract are almost mature. From this point on he or she will gain weight faster. Your baby can now see inside the uterus.

Week 32
By the end of this weeks your baby weighs 4 pounds. He or she is running out of room in the uterus. Your baby can now turn his head from side to side. It's lungs are continuing to mature.

Week 33
Your baby now weighs a little over 4 pounds. It's movements have probably changed because there is less room to move around.

Week 34
By the end of this week your baby weighs about 5 pounds. It's probably in the head down position although there is still time to turn if it isn't.

Week 35
Your baby is now about 20 inches long, and weighs 5 and a half pounds. If you go into labor now, your baby has a 99 percent chance of survival.

Week 36
You will probably start seeing the doctor every week until you have your baby. The uterus is starting to get tight and the baby probably wont move around as much.

Week 37
At the end of this week your pregnancy will be considered full term, meaning your baby wont be considered premature if he or she is born. You baby weighs almost 7 pounds and is about 21 inches long.

Week 38
You may notice that you are starting to breathe easier this week, but you may need to go to the bathroom more often. This is called lightening. It happens when the baby's head goes lower into your pelvis.

Week 39
Your baby is still building a layer of fat to keep it warm after it is born. All of you baby's organ are developed. It weighs from 7 - 7.5 pounds.

Week 40
Your baby will be born any day now. But some babies will wait up to two more weeks to come out. Only 5 percent of baby are born right on their due date.

Week 41
Don't worry if you haven't delivered yet. Just remember it will be soon!!

Week 42
If you are still pregnant by the end of this week your doctor will probably induce you.