The development of a pregnancy occurs in 40 long and wonderful weeks. If you're expecting a baby, you’re probably dying of curiosity to know how it grows week by week.
According to the Australian Government's Better Health Channel Association, this is how the process happens:
Doctors usually use the first day of your last period as the likely start of your pregnancy, since it’s impossible to know exactly when a baby was conceived. Although this is officially the first week of gestation, your uterus is free and ready to be occupied.
At this time there is no embryo developing yet, but if we see this picture it would be like this: an egg is waiting to be fertilized by a sperm and traveling through the fallopian tube.
This is where finally the egg and the sperm meet for the first time. A few hours after being fertilized, the egg will start his journey to settle in the uterus.
Meanwhile, the fertilized egg (known as a zygote) will be divided into 16 identical cells. At this moment the zygote is practically a ball of many cells and is the size of the head of a pin. This is called a blastocyst.
Here is where the embryonic stage begins, and the future baby is so small that you can’t even call it a fetus.
It does not measure more than 1 millimeter and is smaller than a grain of rice. At this time the blastocyst will be divided into two, one half is now called an embryo and it will become a fetus, the other half will become the placenta.
The embryo is the size of an orange seed, in this week it will double its size from 2 to 4 millimeters. The umbilical cord is being formed and by the end of this week the neural tube, the foundation of the brain and the spinal cord will also be ready.
Now the embryo measures approximately 7 millimeters and it has wrinkles and in the next few weeks the face will be formed. The spinal cord continues to grow, so at this moment it looks like a little tail. The embryo still has no limbs and is just a little cocoon that will soon become the arms and legs.
The heart of the embryo is almost formed, and it already beats 110 times per minute. In addition, the placenta and the amniotic sac have already developed, and their head is disproportionately large. The face is more defined, and it already has a mouth, nostrils, ears and black dots that will soon be the eyes.
The embryo is about 1.3 centimeters long and now, in this week the arms and legs will begin to develop, but they will look like fins, since the fingers will still be attach together.
In this week the embryo develops lips, nose and eyelids, the color of its eyes will also be defined.
At this moment the embryo is the size of an olive and all the vital organs have begun to develop. The head is still huge compared to the rest of the body, but the tail is gone, and it has a more of a human form.
Officially it stopped being an embryo to become a fetus that measures approximately 2.5 centimeters. Bones and cartilage are forming, so your limbs will have flexibility. Also, at this point your kidneys will begin to produce urine.
Although we do not see teeth in a baby until his or her 6 months of age, the fetus will start producing them under the gums at this time. Now it measures approximately 4 cm and it will develop taste buds and facial features.
At this time, the head still occupies more than half of its total length, but in the coming weeks his torso will grow. The skin is still transparent, but he or she already has visible nipples. It will also develop the startle reflex, this means that it will hear sounds and react to them by opening and closing his or her arms and legs.
With his developed limbs and a length of approximately 7 centimeters, the fetus will begin to swim. It will also develop the vocal cords, so he can cry silently.
Your fingers are already fully formed (that includes the nails).
At this time the fetus already measures about 8.5 centimeters and will develop the lanugo, a kind of hair all over the body that will keep it warm, this will fall later. Also, your neck will develop more which will allow you to stay straight.
And finally, the ears will begin to develop, and your eyes will begin to become sensitive to light, even if they remain closed.
The fetus is already about 14 centimeters tall and weighs as much as an avocado. The muscles of the face can now move, so this week it will begin to make facial expressions, but still has no control over them.
The fetus will eventually develop eyebrows and eyelashes and a little bit of hair, and it will begin to practice their swallowing skills.
This week you will learn to yawn, and it will also give you hiccups and it’s so big that you will begin to feel its movement. In addition, the nervous system is maturing rapidly, and the brain is now forming complex connections.
In this week the pigmentation in the skin will begin to develop thanks to the melanocytes, so little by little it will stop being transparent. The fetus is as big as a mango.
The fetus will move a lot and you will feel it more because its size reached a size similar to a small melon, about 21 centimeters. It will also strengthen the development of your organs and bones, and the tips of your fingers will develop fingerprints.
The kicks will be present because his limbs finally reached the proportion of the rest of his body. In addition, the brain connections will be more developed and it will begin to send signals to the muscles.
Currently the fetus looks much more like a newborn in appearance, but in size it’s still small, measuring approximately 28 centimeters.
At this time, your baby will develop the sleep and wake cycle, and it’s so great that you will know immediately when is awake and kicking. The sense of hearing will develop further, and he or she will be able to hear external noise more accurately.
In this week the fused eyelids will now be separated in two, which allows to open and close the eyes.
The lungs are even more developed and the baby will begin to practice breathing by inhaling and exhaling amniotic fluid.
The baby will have more hair and his skin will become smoother. During this time, the skin also becomes rosy as its capillaries form below and are fill with blood.
The senses of hearing and sight are beginning to develop very rapidly. Also, if it’s a boy, his testicles will soon begin to drop, a process that can take up to three months.
At this point the baby's eyes have already taken on an almost definite color, because they can change even after birth.
In addition, the brain is extremely active during these days and thanks to this the baby can already distinguish voices.
The baby now weighs about a kilo and measures 37 centimeters and his eyesight is so developed that he can even see the light that passes through the womb.
The same goes for your brain, it’s so developed that when you sleep you will start to have dreams.
The baby will start to get upside down to prepare for delivery and it will also react more to external stimuli such as the foods the mother ingests.
The cells that regulate the temperature of your body will develop further, and the fine hair known as lanugo will begin to disappear.
The brain is also changing its appearance and developing those ridges and grooves that we normally know in the brain.
The baby will be more active than ever and because it grows faster and faster, there will be less space in the placenta, so you can see through the abdomen some of its movements. You will also sleep for longer periods of time and thanks to the fat that accumulates under your skin, your arms, legs and your whole body will look plumper.
In the last weeks in the uterus, the baby will practice the entire time those important skills that will need to be born, from breathing and sucking, to swallowing and kicking.
The skin is no longer transparent and completely opaque, and the baby’s hair, eyelashes, eyebrows and nails are completely formed.
The baby now has fully developed his or her immune system, which generates antibodies and is ready to receive germs from the outside world.
At this moment the baby has his or her first poop between the intestines, which will be defecated when the baby is born. If you wonder where it came from, easy! Your baby ate its own dead cells and his fine hair that covered it to keep it warm.
Now there is less room to move, so instead of kicking, the baby will start to push, you can even see a fingerprint through the abdomen. Now that he is so close to being a fully functioning human being, he will spend the rest of his time in the womb gaining weight.
Week 36 to 39
From now on, the baby will measure 40 centimeters and it will grow rapidly until it reaches a length of 50 centimeters in week 39. At this point the baby should be perfectly placed with his or her head down and although it would be ready to be born, its brain and lungs will develop a lot in these last weeks, it will also gain more weight.
Basically he or she is already a small human being, there are small changes such as the color of the iris, also it will be detached from the lanugo and as their kidneys are functioning perfectly, the baby does not stop urinating.
Thanks to the thick layer of fat under your skin, your body looks very plump and adorable. That layer of fat will also help control the temperature of your body after birth.
At this time, the baby is about 51 centimeters in length and is more than ready to be born.
*Translated from the original article by Gabriela Nava published on VIX Español
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