Weeks: 1 - 4 The fertilized egg becomes a two celled organism, and this period is considered to be the period of rapid and fragile growth in preg...
Weeks: 1 - 4
The fertilized egg becomes a two celled organism,
and this period is considered to be the period of rapid and fragile growth in pregnancy. Zygote which is the fertilized egg, divides approximately 18-36 hours after fertilization to become a two-celled organism, and then by 48-72 hours, it becomes a morula, consisting of 16 cells. While this growth is occurring, the cell cluster is moving through the fallopian tube to the uterus. Then in about four days, the morula, now 32 cells, reaches the uterus.
This is the time when the baby’s liver and digestive system starts to develop, and then the placenta and the maternal blood supply to the placenta begin to develop. The embryo at this time becomes double layered, namely the endoderm and the ectoderm. Also, the chorion becomes the foundation of a third layer, the mesoderm.
The third week progress
A very important time during which we find that the foundation for the muscular system, skeletal system, cardiovascular system, lymphatic system and parts of the integumentary (skin, hair, nails), endocrine, respiratory, urinary and reproductive systems get laid.
At the same time, the endoderm lays the foundation for the digestive system parts of the reproductive, urinary, respiratory, and endocrine systems.
The thyroid begins to develop and early muscle cells are formed. This is also the time for the limb buds, lung buds, tongue bud, parathyroid, lens, thymus, and the urinary and reproductive systems to start developing.
Weeks: 5 - 8
The digestive system is formed during this time, which means the stomach, liver, pancreas, gall bladder, spleen and intestines all blossom from the inner layer, the endoderm. The fetus hits the size of a grape, and the head and facial features have human characteristics, with closed eyelids, ears, and a mouth. Cartilage supports the arms, legs, fingers and toes, because the bone formation and hardening process is not complete. The external genitalia also form and the lungs develop their separate lobes.
Weeks: 9 - 13
During this time the fetus will develop each body system, and will further mature these systems in the months to come. Also, the baby’s kidneys are now functioning, hair is growing, the fingers and toes are more prominent, and tooth buds are forming.
Weeks: 14 - 17
The fetus at this time swallows the amniotic fluid and is able to eliminate this by urinating. The body is covered with a fine downy hair called lanugo, which protects the skin. The fetus is now almost 3 times the size and 5 times the weight of last month -- measuring about 6 inches long and weighing about 5 ounces.
Weeks: 18 - 21
The pregnancy has now reached halfway mark, and the signs of life are evident with a bulging tummy obvious from the outside.
The heart is now beating and mom can feel the first fetal movements, and is first felt around week 20 of pregnancy. Most women find this very exciting – proof that you’ve got something special going on!
Weeks: 22 - 26
Now, the fetus’ skin is becoming less transparent as the fetus steadily gains fat and the integumentary system continues to grow. The baby’s internal organs are continuing to develop and become stronger, so much so that the fetus can hear and becomes startled at loud bangs.
The top of uterus goes past the navel, and makes a woman look distinctively pregnant.
The baby is now 11-14 inches long and weighs about 2 pounds.
Weeks: 27 - 30
Bones begin to harden during this month, and the eyelids can now can open and close. The hair, including eyelashes now becomes thicker and darker. Growth is rapid with the fetus gaining more fat – the weight is now about 3 pounds and the length is 15-16 inches.
Weeks: 31 - 35
The fetus now turns to a head down position and snuggles into the pelvis, and of course the space is getting a little cramped and rapid fluttery movements are fewer. Thus you may feel more thumps and heavy kicks.
Weeks: 36 - 40
At this time the baby is about 1/2 a pound a week. The uterus is almost at full capacity, and the baby has dropped down into the pelvic inlet or birth canal. The fetus will shed some of the protective lanugo and cheese-like skin coating. The fetus also produces high amounts of the hormones - oxytocin, cortisol and prostaglandin - around the time of delivery. The average weight is 6-9 pounds and length is 20 or more inches.
