Stages of Pregnancy
First Trimester
Week 2: The fertilized cell is called a zygote and contains 23 chromosomes from each parent. These chromosomes will determine hair and eye color, height, skin tone, and sex. At this point the embryo is the size of a grain of salt.
Week 4: The placenta, an organ that develops during pregnancy and is attached to the baby via the umbilical cord, begins to form and the embryo is firmly implanted in the lining of the uterus
Week 6: The embryo is now about 1/5 of an inch lon and is developing arms, legs, lungs, intestines and a brain. There is also a very small heart that has formed and is beating.
Week 8: The ears and nose appear and the embryo is now recognizable as a baby on a picture. Eyes are beginning to form and by week nine the baby begins to move around.
Week 10: The fetus is now approximately one inch in length. Bones, joints, fingers and toes are taking shape, and the fetus now has fingerprints. Several internal organs begin to function and the nervous system is getting up and running.
Week 12: The baby's liver and kidney's are functioning and the hair and nails have started to grow.
Second Trimester
Week 14: The fetus is about 3-incheslong and weighs approximately one ounce. Muscles are developing and the baby is really beginning to move around.
Week 16: The fetus is now between four and five inches long and weights a little under 3 ounces. The baby can now make a fist and is more sensitive to light.
Week 18: The brain begins hooking up to the ears through various nerves and the baby may now be sensitive to loud noises.
Week 20: This is the halfway point. The baby is about six inches long and weighs around nine ounces. The mother will begin feeling the baby move around more.
Week 22: The baby is now around one pound and beginning to experiment with touch by feeling his or her face and hands.
Week 26: The baby now weighs about 1 1/2 to 2 pounds and the hair on the head is thicker and more
developed. The baby's eyes are still closed, but the lashes and eyebrows are fully formed.
Third Trimester
Week 28: The eyes often open by this week and the color has been established. The baby is now sleeping for thirty minutes at a time, and movements become much more pronounced when the baby is awake.
Week 30: Now the baby is up to about three pounds, but this week is when he or she really starts to put on the weight. The baby will now gain approximately 1/2 pound a week from here until week 37 or 38.
Week 34: The lungs are more completely developed and the pasty white coating that protects the baby's skin gets thicker.
Week 36: At this point the baby is anywhere between 15 and 19 inches in length, and weighs about 6 1/2 pounds. The baby may turn into the head down position at this time to get ready for birth.
Week 38: The baby is now considered full-term and weighs on average about seven pounds.
Week 40: The baby's official due date. Chances are the baby is between 19 and 21 inches long and weighs between 7 and 8 pounds.