What develops first in a baby
Stages of Fetal Development - First Trimester
Stages of Fetal Development - First TrimesterStages of Fetal Development - First Trimester
One - 13 Weeks
| FERTILIZATION Biologically speaking, fertilization (or conception) is the beginning of human development. Fertilization normally occurs within several hours of ovulation (some authors report up to 24 hours) when a man's sperm combines with a woman's egg | |
| WEEK 2
| |
| WEEK 4
| |
| WEEK 6
| |
| WEEK 8
| |
| WEEK 10
| |
| WEEK 12
| |
Your Baby's Development: The First Trimester
From the moment of conception to the time of delivery, your growing baby goes through several stages of development. The first third of your pregnancy is called the first trimester. It’s made up of weeks 1 through 12 or 13 of pregnancy. Here is a summary of how your baby develops during the first trimester.
Path to improved health
Pregnancy begins when a man’s sperm fertilizes a woman’s egg. Since you don’t always know when fertilization occurred, doctors calculate pregnancy based on the first day of your last menstrual period (LMP). Your doctor will count forward 40 weeks from your LMP to estimate the due date. Most births occur between weeks 38 and 42.
If you have an ultrasound early in your pregnancy, your doctor may measure the baby to determine your due date instead.
After conception, your baby begins a period of dramatic change known as the embryonic stage. This stage runs from the 5th through the 10th week of pregnancy. During this stage, the baby is called an embryo.
There are numerous changes that occur during the embryonic stage. First, the cells of the embryo (called embryonic stem cells) multiply and develop. They become the hundreds of different types of cells needed to make a whole human body. Your baby’s major organs and body parts begin to take shape.
The placenta forms during the embryonic stage. The placenta takes nutrients, oxygen, and water from your blood and passes these along to your baby through the umbilical cord. It also removes the baby’s wastes. The placenta will filter out most of the harmful substances that may be present in your body.
The amniotic sac forms during this stage as well.
It is filled with amniotic fluid, which surrounds and protects your baby in the uterus.
Below are some of the highlights that occur during the embryonic stage.
- Nervous system. This is one of the first things to develop. It includes the formation of your baby’s brain, spinal cord, and nerves.
- Heart. An S-shaped tube forms on the front of the embryo. This will become your baby’s heart. At first the heart doesn’t beat, but soon it starts beating and pumping an early form of blood.
- Face. Your baby’s facial features begin to take shape. The eyes and ears form on the sides of the head and are linked to the brain. The eyes move forward on the face, and eyelids form to protect the developing eyes. Pieces of tissue grow and join together to create the forehead, nose, cheeks, lips, and jaw. The nasal passages, mouth, and tooth buds form the baby’s first teeth. A tongue with taste buds also forms.
- Arms and legs.
At first, your baby’s arms and legs begin as little buds that sprout from the embryo’s sides. As they grow, the arms look like paddles and the legs look like flippers. A ridge appears on the end of each one. They eventually become your baby’s fingers and toes. - Sexual organs.Cells form to become your baby’s eggs or sperm. Your baby’s vagina or penis is visible at the end of the embryonic period. However, it’s still too soon to tell on an ultrasound if your baby is a girl or boy.
- Muscles and movement.Muscles develop and the embryo begins to move. At first it’s only twitching and reacting to touch. Once the nerves and muscles start working together, your baby can start moving on purpose.
By the end of the embryonic stage at week 10 of your pregnancy, your baby will be about 1 inch long. That’s still too small for you to feel your baby’s movements. You’ll probably feel them starting in the middle of the second trimester.
After the embryonic stage, the fetal stage begins and your baby is called a fetus. This stage runs from the 11th week until birth. Your baby will grow longer and gain weight quicker. His or her organs and body parts will continue to develop. Fingernails and toenails begin to form and the kidneys start working. By the end of the first trimester, your baby has tripled in length to about 3 inches long.
Things to consider
As your baby develops in the womb, your body goes through a lot of changes as well. Make an appointment with your doctor if you think or know you’re pregnant. He or she will be able to confirm your pregnancy. Your doctor will also talk with you about your baby’s development and prenatal care. So much important development happens during the first trimester. It is important to not take any medicines without first asking the advice of your doctor.
Questions for your doctor
- Am I pregnant?
- How far along am I in my pregnancy?
- What weeks do you consider to be the first trimester?
- What lifestyle changes should I make to support my baby’s development?
- Are there any risks to the baby or me that I should be aware of?
Resources
American Academy of Family Physicians: Changes in Your Body During Pregnancy: First Trimester
March of Dimes: Pregnancy Week by Week
National Institutes of Health, MedlinePlus: Fetal Development
Copyright © American Academy of Family Physicians
This information provides a general overview and may not apply to everyone.
Talk to your family doctor to find out if this information applies to you and to get more information on this subject.
Child development by week | Regional Perinatal Center
Expectant mothers are always curious about how the fetus develops at a time when it is awaited with such impatience. Let's talk and look at the photos and pictures of how the fetus grows and develops week by week.
What does the puffer do for 9 whole months in mom's tummy? What does he feel, see and hear?
Let's start the story about the development of the fetus by weeks from the very beginning - from the moment of fertilization. A fetus up to 8 weeks old is called embryo , this occurs before the formation of all organ systems.
Embryo development: 1st week
The egg is fertilized and begins to actively split. The ovum travels to the uterus, getting rid of the membrane along the way.
On the 6th-8th days, implantation of eggs is carried out - implantation into the uterus.
The egg settles on the surface of the uterine mucosa and, using the chorionic villi, attaches to the uterine mucosa.
Embryo development: 2-3 weeks
Picture of embryo development at 3 weeks.
The embryo is actively developing, starting to separate from the membranes. At this stage, the beginnings of the muscular, skeletal and nervous systems are formed. Therefore, this period of pregnancy is considered important.
Embryo development: 4–7 weeks
Fetal development by week in pictures: week 4
Fetal development by week photo: week 4
Photo of an embryo before the 6th week of pregnancy.
The heart, head, arms, legs and tail are formed in the embryo :) . Gill slit is defined. The length of the embryo at the fifth week reaches 6 mm.
Fetal development by week photo: week 5
At the 7th week, the rudiments of the eyes, stomach and chest are determined, and fingers appear on the handles.
The baby already has a sense organ - the vestibular apparatus. The length of the embryo is up to 12 mm.
Fetal development: 8th week
Fetal development by week photo: week 7-8
The face of the fetus can be identified, the mouth, nose, and auricles can be distinguished. The head of the embryo is large and its length corresponds to the length of the body; the fetal body is formed. All significant, but not yet fully formed, elements of the baby's body already exist. The nervous system, muscles, skeleton continue to improve.
Fetal development in the photo already sensitive arms and legs: week 8
The fetus developed skin sensitivity in the mouth (preparation for the sucking reflex), and later in the face and palms.
At this stage of pregnancy, the genitals are already visible. Gill slits die. The fruit reaches 20 mm in length.
Fetal development: 9–10 weeks
Fetal development by week photo: week 9
Fingers and toes already with nails.
The fetus begins to move in the pregnant woman's stomach, but the mother does not feel it yet. With a special stethoscope, you can hear the baby's heartbeat. Muscles continue to develop.
Weekly development of the fetus photo: week 10
The entire surface of the fetal body is sensitive and the baby develops tactile sensations with pleasure, touching his own body, the walls of the fetal bladder and the umbilical cord. It is very curious to observe this on ultrasound. By the way, the baby first moves away from the ultrasound sensor (of course, because it is cold and unusual!), And then puts his hands and heels trying to touch the sensor.
It's amazing when a mother puts her hand to her stomach, the baby tries to master the world and tries to touch with his pen "from the back".
The development of the fetus: 11–14 weeks
Development of the fetus in the photo of the legs: weeks 11
The baby, legs and eyelids are formed, and the genitals become distinguishable (you can find out the gender (you can find out the gender child).
The fetus begins to swallow, and if something is not to its taste, for example, if something bitter got into the amniotic fluid (mother ate something), then the baby will begin to frown and stick out his tongue, making less swallowing movements.
Fruit skin appears translucent.
Fruit development: Week 12
Photo of the fetus 12 weeks per 3D Ultrasound
buds are responsible for production for production urine. Blood forms inside the bones. And hairs begin to grow on the head. Moves more coordinated. The skin turns pink, the ears and other parts of the body, including the face, are already visible. Imagine, a child can already open his mouth and blink, as well as make grasping movements. Baby sucks his thumb, becomes more energetic. Pseudo-feces are formed in the intestines of the fetus - meconium , kidneys begin to work. During this period, the brain develops very actively. The auditory ossicles become stiff and now they are able to conduct sounds, the baby hears his mother - heartbeat, breathing, voice. The fetus intensively gains weight, fat deposits are formed. The weight of the fetus reaches 650 g, and the length is 300 mm. The lungs at this stage of fetal development are so developed that the baby can survive in the artificial conditions of the intensive care unit. Lungs continue to develop. Lips and mouth become more sensitive. The eyes develop, open slightly and can perceive light and squint from direct sunlight. In girls, the labia majora do not yet cover the small ones, and in boys, the testicles have not yet descended into the scrotum. Fetal weight reaches 900–1200 g, and the length is 350 mm. 9 out of 10 children born at this term survive. The lungs are now adapted to breathe normal air. Breathing is rhythmic and body temperature is controlled by the CNS. The baby can cry and responds to external sounds. Child opens eyes while awake and closes during sleep. The skin becomes thicker, smoother and pinkish. Starting from this period, the fetus will actively gain weight and grow rapidly. The fetus reacts to a light source. Muscle tone increases and the baby can turn and raise his head. On which, the hairs become silky. The child develops a grasping reflex. The lungs are fully developed. The fetus is quite developed, prepared for birth and considered mature. The baby has mastered over 70 different reflex movements. Due to the subcutaneous fatty tissue, the baby's skin is pale pink. The head is covered with hairs up to 3 cm. The baby perfectly mastered the movements of his mother , knows when she is calm, excited, upset and reacts to this with her movements. During the intrauterine period, the fetus gets used to moving in space, which is why babies love it so much when they are carried in their arms or rolled in a stroller. The nails protrude beyond the tips of the fingers, the cartilages of the ears and nose are elastic. In boys, the testicles have descended into the scrotum, and in girls, the large labia cover the small ones. The weight of the fetus reaches 3200-3600 g, and the length is 480-520 mm. After the birth, the baby longs for touching his body, because at first he cannot feel himself - the arms and legs do not obey the child as confidently as it was in the amniotic fluid. Therefore, so that your baby does not feel lonely, it is advisable to carry him in your arms, press him to you while stroking his body. And one more thing, the baby remembers the rhythm and sound of your heart very well . Therefore, you can comfort the baby in this way - take him in your arms, put him on the left side and your miracle will calm down, stop crying and fall asleep. In the book “280 Days Before Your Birth” (Bombora Publishing House), Norwegian biochemist Katarina Vestre talks about the stage-by-stage development of the fetus in the mother’s womb – at what point the sex of the unborn child is determined, which of of all organs begins to form the earliest and why the first two pairs of kidneys are not suitable for life. "Snob" publishes one of the chapters of By the beginning of the third month, you are already the size of a strawberry. You have a wide and flattened nose, your eyes are far apart. With a high forehead and large head, you look a bit like an alien, but over the next few weeks you will acquire quite human features. Your dark eye circles will be covered by thin eyelids, the crooked head will straighten a little more, the chin will grow, and the neck will become more pronounced. This month it will finally be possible to understand who you will become - a boy or a girl. For the first few weeks, there is no difference between the sexes, which is probably why boys also have nipples - not that they need them, they just form before the gender differences appear. Even the internal genital organs are one and the same generalized structure. Regardless of the sex of the embryo, two sacs are formed, both attached to small tubules. But in the seventh week, the transformation begins, and your genes will have to decide what will happen next: if you have a Y chromosome in the last pair of chromosomes, then these sacs will become testicles; if there are two X chromosomes, then they will turn into ovaries. The Y chromosome itself looks pretty pathetic. It contains very few genes - somewhere around 50-60. For comparison, the X chromosome, which is found in both women and men, contains between 800 and 900 genes. At an early stage of development, in an embryo destined to become a girl, one of the two X chromosomes will turn off forever. The choice of two X chromosomes is completely random, that is, part of the cells will use the X chromosome inherited from the mother, and the other part will use the father's X chromosome. Because of this, all women are like a prefabricated genetic hodgepodge. The consequences of such mixing are especially visible in cats: since the gene that affects coat color is located on the X chromosome in them, females, unlike males, can be all kinds of variegated colors. Some cells are pigmented according to the recipe inherited from the father, while others get the mother's recipe, the color of which may differ markedly. The key gene on the Y chromosome is called SRY. The first hormone they send starts the reconstruction of one of the tubules attached to the ovaries. In women, this channel remains intact, and subsequently the ovary and uterus are formed from it. The second canal, extending from the other testicle, remains in place - it will soon turn into a seminal canal. Then the cells of the testicles begin to produce a large amount of testosterone, which seems to call: "Become a man!" This message is carried throughout the body, and soon after that the sex differences become clearly visible. Scientists conducted experiments on rabbit embryos, in which the gonads were removed in the early stages of development. No wonder misunderstandings happen in such a complex system. What happens if the cells never hear the testosterone calls of the testicles? On the surface of the cells are testosterone receptors that pick up these messages and transmit them into the cell. If these receptors turn out to be faulty, then the cells simply will not be able to hear the signal (the hormone will be produced in vain) and will continue to create a body with female sexual characteristics. Outwardly, people with this genetic disorder - hermaphrodites - can be indistinguishable from ordinary women, since the fate of the external genitalia is determined by the testosterone signal. Not all animals allow chromosomes to determine their sex. So, alligators grant the right to choose their own fate to the environment. If in the first three weeks the alligator egg develops at a temperature of less than 30 degrees, then a female will hatch from it. If the temperature exceeds 34 degrees, then the male will begin to develop in the egg. An even stranger way of determining the sex of its offspring is using a specific marine worm called Bonellia viridis. It begins its existence as a tiny asexual larva, which swims in the ocean for some time, after which it sinks to the bottom. From where exactly she lands, her fate depends entirely. If the larva lies on a free area of the seabed, then it will become a female about a centimeter long. It's hard to describe exactly what a female Bonellia viridis looks like: try to imagine an alien with a gherkin-like body and an algae-like tail. This creature spends the rest of its life attached to the seabed, feeding on the remains of small animals and plants. If the larva does not land on a free area of the seabed, but gets on the skin of a female of its own species, then it will immediately turn into a tiny male only one to three millimeters long. Having reincarnated, the male crawls into the body of the female, where he spends the rest of his days as a personal sperm donor. As a token of gratitude, the female shares her food with the parasite. Of all the love relationships that can only be found in nature, these are perhaps the most intimate in the truest sense. And there are also animals that, in the event of a change in environmental conditions, are generally able to change their sex throughout their lives. Take, for example, Thalassoma bifasciatum (blue-headed thalasso), a fish that lives in the coral reefs of the Caribbean. If the “husband” suddenly dies for some reason, then he will immediately find a replacement. One of the females, usually the largest, will immediately turn into a male. In just one day, her ovaries shrivel up and are replaced by male gonads, so the future of their coral colony is safe. If the fetus has a Y-chromosome and the chemical signal reaches the desired target, then the penis begins to form. It develops from a small tubercle that becomes the clitoris in girls. About three months after conception, this tubercle grows so much that the sex of the fetus can be determined with the naked eye. The boy's testicles, however, are still inside, where they will be until the seventh month. First, they will gradually descend into the stomach, and then reach the scrotum.
Development of the fetus for weeks: Week 14 9000 9000 Fetal development: 15-18 weeks
Fetal development by weeks photo: week 15 
The fetus begins to actively push in the mother's tummy. The sex of the fetus can be determined by ultrasound. Fetal development: 19-23 weeks
Fetal development by week photo: week 19
Fetal development by week photo: week 20 Fetal development: 24-27 weeks
Now the baby is already falling asleep and waking up. Downy hairs appear on the skin, the skin becomes wrinkled and covered with grease. The cartilage of the ears and nose is still soft.
Fetal development by week photo: week 27 Fetal development: 28-32 weeks
Almost all babies born prematurely at this time are viable. The weight of the fetus reaches 2500 g, and the length is 450 mm. Fetal development: 33-37 weeks
Fetal development by week photo: week 36 Fetal development: 38-42 weeks
Fetal development by weeks photo: week 40 
For a baby, this is a completely natural state, so he will calm down and fall asleep when he is rocked. 
And for you, finally, the time of bliss will come :) . How a fetus develops in the mother’s womb — Snob
This is necessary so that the cells do not double the production of everything that is contained in the X chromosome. The more copies of the recipe available, the more chefs will get to work and the more they will end up with. When one of the X chromosomes is disabled, the embryo already consists of a large number of cells. 
Without it, cells by default begin to form ovaries. The protein produced by the SRY gene does little by itself, but it acts as a switch that activates other genes distributed across different chromosomes. Together, these genes start the process of forming testicles, which after some time begin to produce hormones that spread throughout the small body. 
As a result, all embryos turned into rabbits, even those that carried the Y chromosome. Thus, it is the testicles that are required to tell the whole body that the embryo should become a boy. If other cells do not hear this signal, they will form the body of a female. 
Inside, however, they will have glands behaving like testicles, while the ovaries and uterus will be absent - the tubule from which they form has long been destroyed by the order of the testicles. In general, gender development is an extremely complex process that is not limited to the Y chromosome. 
If the male of this fish gets into a coral reef guarded by another male, he will not try to take his place. He will simply turn into a female and live quietly with the rest of the girls in this small coral harem. 
