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Week 1
Week 1 marks the beginning of the first trimester and is also the last period a woman will have until after the baby is born. No egg has been fertilized yet but as this is the beginning of the next menstrual cycle it marks the beginning of the pregnancy. -
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The First Trimester
During this 13 week period the baby-to-be has gone through quite a few stages of development already. Starting out as a single cell that multiplied and burrowed into the uterine wall, growing weekly as an embryo. The embryo grew organs, including a beating heart, developed facial features, created bone and muscle, and the beginning of the nervous system. At week 8 the unborn baby becomes a fetus and continues to grow and develop. -
Week 2
During Week 2 an egg will be released from the ovary and fertilized by a male's sperm. The egg will start to undergo mitotic division known as cleavage. This week marks the conception of the baby.http://www.baby2see.com/development/2weeks.jpg -
Week 3
While the newly formed zygote is going through cleavage it travels through the fallopian tube and into the uterus. The zygote will float freely for about 3 days until it implants itself into the uterine wall. -
Week 4
After implantation the fertilized egg becomes a blastocyst which contains about 50 to 60 cells which are still quickly multiplying. Hormones get released which tell the body to not shed the endometrium. At this stage the embryo is about a one-hundredth of an inch long. -
Week 5
The placenta is starting to grow and the embryo has completely grown into the uterus. The embryo will double in size from 2mm to about 4-5mm during this week. Nerve growth begins at the back of the embryo which will eventually grow into the spinal cord. -
Week 6
The embryo is about 8mm long at this point. It is starting to make blood vessels and cells and actually has a small beating heart. The spinal cord is starting to close up and the cells which will become the arms and legs are starting to form. -
Week 7
At this point the arms and legs are starting to grow as well as the lungs, liver, pancreas, and thyroid gland. The lower jaw is starting to grow and a mouth opening is made. The eyes can actually be made out at this point. -
Week 8
The arms and legs have started to elongate and the handds and feet have started to appear. The baby will actually start moving now but the mother can't feel it yet. The face is being formed as well as the mouth and nose. -
Week 9
The embryo is 30 mm in length and is developing quickly. Bones and cartilage start to form. More facial features are developing such as eyelids and lips. The heart is actually completed and the brain is starting to grow rapidly. This also the week where the anus is starting to form. -
Week 10
This is an exciting week because from now until birth the baby will be called a fetus! The body muscles are still developing but very near completion which means the baby is shifting and moving around in the amniotic fluid. Fingerprints have taken shape and nipples and hair follicles are made. -
Week 11
At this stage fingers and toes are no longer webbed together. The gender is starting to matter now because if the fetus is male the testicles being to produce testosterone. The fetus is starting to grow teeth and can also swallow now. -
Week 12
The fetus can move spontaneously now and is about 2.5 inches long. The face which is starting to fully develop looks like an actual human. The pancreas has also started to create insulin. -
Week 13
The fetus has grown to 3 inches in length and weighs a whole ounce now. Bone is replacing cartilage and the nose and chin are well defined and shapely. The genitalia may or may not be well enough defined to actually tell wether the feuts is a boy or girl. -
Week 14
The fetus' eyes start to move to the center of the face as well as the ears fully developing. For girls, the ovaries will begin to move towards the pelvis and for males the prostate gland begins development. -
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The Second Trimester
There is not much development during this period, mostly the fetus will grow, A LOT. The abdoment will swell noticeably throughout this stage. -
Week 15
Development begins to slow during week 15 as the baby is now 4 inches long and weighs about 2.5 ounces. One notable thing about week 15 is that the baby has actually grown fingernails and toenails. -
Week 16
The fetus is growing fairly quickly and is now 5 inches long and has gained another ounce, 3.5 in total. The fetus learned to breathe and now inhales and exhales small amounts of amniotic fluid. The abdomen is swelling. -
Week 17
The fetus swallows up to a litre of amniotic fluid a day which means it is also starting to develop stool. The fetus is 9 inches long from head to toe if it were able to stretch out. -
Week 18
The fetus develops vernix which is a waxy protective layer to help protect the skin from months in water. They can hear noises and can actually be scared by sudden loud noises. The alveoli form in the lungs. -
Week 19
The fetus has full blown genitals and if it is a girl, has developed about 6 million eggs. It is also starting to grow hair on the scalp. -
Week 20
Week 20 marks the halfway point of pregnancy! The baby is now 11 ounces. It begins to grow hair on the rest of the body and the skin is also getting thicker. The fetus is also now able to recognize the voice of the mother. -
Week 21
The fetus length is now measured from the head to the heel and is 10.5 inches long. The bone marrow has begun to make blood cells. Depending on the size of the head, estimates can be made to the date of birth. -
Week 22
The fetus starts a regular sleeping pattern and gains about 70 grams a week. The abdomen is not very large at this point but is is indeed noticeable. -
Week 23
The unborn baby is about 11 inches and weighs about a pound. The pancreas begins producing insulin which means it can process sugars. -
Week 24
The baby is gaining a lot of weight, mostly in muscle and bone but also some baby fat, it is starting to look more and more like a newborn. -
Week 25
The brain ahs been growing rapidly this whole time and the sexual organs are now fully developed. -
Week 26
At this point the mother may begin to experience Braxton Hicks contractions whicha re small regular contractions that prepare the uterus for birth.
The fetus starts to open their eyes at this time. -
Week 27
The fetus weighs about 2 pounds at this point. The hearing continues to develop and the fetus can blink and look around. -
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The Third Trimester.
The time has almost come to give birth which means the baby is very developed and is moving around frequently. During this three motnth time period the lungs will finish developing and the baby's eyes will start to respond to stimuli. Any baby born past 36 weeks will have amazing chances of survival and even if they are born 34-36 weeks in they will most likely survive. -
Week 28
The fetus is experiencing REM sleep which means it is also dreaming. Now that the branches of the lungs are so developed the chances of a premature child surving at this point are much higher. -
Week 29
The fetus' muscles and lungs continue to mature all while the brain is developing billions of neurons. The baby is moving around quite a bit so the mother should be able to feel it from time to time. -
Week 30
At this point the baby's skin is starting to get smoother and it can also control its own temperature. If the baby is a boy, its testes will move down from the abdomen and into the groin. -
Week 31
At this point the baby weighs around 3.5 pounds and measures in at 16.5 inches head to heel. The eyes are open now and respond to stimuli. -
Week 32
The baby is developing more and more adipose tissue under the skin. Previously in boys the testicles were descending to the groin, now they are dropping to the scrotum. -
Week 33
The baby will drink about a pint of amniotic fluid a day now and the mother will gain somewhere around a pound a week. Most of the weight is going to the baby. -
Week 34
Although still premature if the baby were born at this time it would have an excellent chance of survival. The baby is 18 inches long and weighs 5-6 pounds. -
Week 35
The fetus has coordinated reflexes and is growing rounder due to the layers of fat. Lungs are nearly fully developed and about 90% of the babies born this week survive. -
Week 36
The previous Braxton Hicks contractions will most likely continue in preparation for birth. The baby may be ready to be born any time now. -
Week 37
The baby is now considered at term, meaning it will no longer be premature if born at this time. The water may break at time which would mean going into labor. -
Week 38
The baby may have reached its final birth position: head first. The baby could have a full head of hair at this point although some are born with less. Body fat will continue to build up at this time. -
Week 39
The baby is about 20 inches long and weighs 7-8 pounds. It will be very cramped inside the uterus from now until birth. The fetus will continue to punch and kick at this time. -
Week 40
It is finally time, the baby is now due! Contractions may happen at any time now. Some babies may be born in the next two weeks but that does not mean they are overdue. The baby is only overdue after the 42nd week. The baby will be ready and settled into the birthing position.
