The process of fetal formation and development week by week

This is an automatically translated article.

The article is professionally consulted by Dr., Doctor Ngo Thi Uyen - Obstetrician and Gynecologist - Department of Obstetrics and Gynecology - Vinmec Nha Trang International General Hospital

Pregnancy and motherhood is a woman's sacred responsibility. From a fetus after 40 weeks of "brooding" to giving mother a small angel is an inspiring journey with sweat and tears. According to the World Health Organization (WHO), vaccination for pregnant women is an important step to prevent certain bacteria and viruses that cause illness for both mother and baby during 9 months and 10 days of pregnancy. Therefore, mothers also need to keep in mind the vaccines that need to be given before and during pregnancy.

Week 2: Conceive


This week, you just ovulated. The egg is fertilized within 12-24 hours after the sperm meets the egg. If all goes well, this simple biological event begins a series of increasingly complex processes that create a new person. Over the next several days, the fertilized egg will continue to divide into many cells as it travels down the fallopian tube, into the uterus and begins to penetrate the lining of the uterus.

Thai nhi tuần thứ 2.
Thai nhi tuần thứ 2.

Week 3: Nesting


Now nestled in the nutrient-rich lining of the uterus is a microscopic ball of hundreds of cells that multiply at lightning speed. This ball, called the blastocyst, has begun to produce the pregnancy hormone hCG, upon this signal the ovaries will stop releasing an egg.

Thai nhi tuần thứ 3
Thai nhi tuần thứ 3

The 4th week


Our ball is now officially called an embryo. It's been about 4 weeks since the first day of your last period, which is usually when your next period should appear. At this time, home pregnancy tests will give positive results. At this point, our little friend is only the size of a poppy seed.

Thai nhi tuần thứ 4
Thai nhi tuần thứ 4

Week 5


Although he looks more like a tadpole than a human, he is growing very fast. The circulatory system is starting to form and the little heart will start beating this week. Baby is only as big as a sesame seed at this week of pregnancy.

Thai nhi tuần thứ 5
Thai nhi tuần thứ 5

6th week


Your baby's nose, mouth and ears begin to take shape, and the intestines and brain also begin to develop. Baby is 4-7mm (about the size of a green pea).

Thai nhi tuần thứ 6
Thai nhi tuần thứ 6

Week 7


The little boy has doubled in size since last week, his tail is still there but will disappear soon. Tiny hands and feet that looked like oars were growing from growing arms and legs. At this time, the length from the head to the bottom of the baby is about 9-15mm (about the size of a peanut).

Thai nhi tuần thứ 7
Thai nhi tuần thứ 7

Week 8


The little one starts to move around, but mom can't feel it yet. Nerve cells begin to branch, forming the primitive nervous system. The respiratory tube begins to extend from the throat to the developing lungs. Her current size is from 16-22mm.

Thai nhi tuần thứ 8
Thai nhi tuần thứ 8

9th week


Your basic form is already formed, even with pretty little earlobes, but the road is still long. The fetal tail is gone. She weighs only a fraction of an ounce, but you're about to gain weight fast. Mom, she's as big as a grape (head-butt length 23-30mm).

Thai nhi tuần thứ 9
Thai nhi tuần thứ 9

10th week


Our little friend has completed the most important part of the development process. Your skin is still translucent, but your little hands and feet can be folded and stretched, and small details like nails have begun to take shape. She has a head-butt length of 31-40mm.

Thai nhi tuần thứ 10
Thai nhi tuần thứ 10

11th week


Our angel is almost fully formed. Even though mom can't feel it yet, she can kick her legs, stretch, and even hiccup because her diaphragm is developing. At this point, she has a head-butt length of 41-51mm.

Thai nhi tuần thứ 11
Thai nhi tuần thứ 11

12th week


This week your little reflexes begin: Your fingers will soon begin to flex and stretch, your toes will curl, and your mouth will make sucking movements. She'll feel it when you gently touch her belly - even though she can't feel your movements yet. Your baby has grown as big as a lemon!

Thai nhi tuần thứ 12
Thai nhi tuần thứ 12

13th week


This is the last week of the first trimester of pregnancy. Your tiny fingers now have fingerprints, veins and internal organs clearly visible through the skin. If you're carrying a girl, your baby's ovaries contain more than 2 million eggs.

Thai nhi tuần thứ 13
Thai nhi tuần thứ 13

Entering the second trimester: What to expect?


After the first trimester, miscarriages are less common. For many moms-to-be, early pregnancy symptoms like morning sickness and fatigue are gone. If you feel more energetic now and haven't exercised before, this is a good time to start a regular pregnancy exercise routine.

Thai nhi giữa thai kỳ
Thai nhi giữa thai kỳ

Week 14


Your small brain now has nerve impulses and she can also move her facial muscles. The kidneys are also working. You can even see her sucking her thumb on the ultrasound now! My baby is now as big as a lemon! (head-butt length about 87 mm).

Thai nhi tuần thứ 14
Thai nhi tuần thứ 14

15th week


Your baby's eyelids are still closed, but he can still perceive light. If the mother shines the light on her belly, the baby will avoid the light. This week's ultrasound will reveal your baby's sex. Baby is the size of an apple this week.

Thai nhi tuần thứ 15
Thai nhi tuần thứ 15

Week 16


Your baby's scalp is starting to take shape, although no hair is visible yet. The small legs have now developed, when the mother can feel the fetus. Your little head is now straighter, and your ears are close to the correct position. Our little friend is now about the size of an avocado.

Thai nhi tuần thứ 16
Thai nhi tuần thứ 16

17th week


Our little one can now move his joints, and his skeleton - formerly soft cartilage - is now ossifying. The umbilical cord is getting stronger and thicker.
Mom's baby is the size of a radish.

Thai nhi tuần thứ 17
Thai nhi tuần thứ 17

Week 18


Baby is stretching his arms and legs, and mom can feel these lovely movements. Inside, a protective layer of myelin is forming around your nerve.
This week your baby weighs about 190 grams!

Thai nhi tuần thứ 18
Thai nhi tuần thứ 18

19th week


Your baby's senses - smell, sight, touch, taste and hearing - are developing and he can hear your mother's voice. You can talk, sing or read aloud to your baby if you like.
Your baby weighs about 240 grams.

Thai nhi tuần thứ 19
Thai nhi tuần thứ 19

20th week


Your baby can now swallow and her digestive system is making the sticky, dark, sticky meconium she will give on the first defecation - in a diaper or in the womb when you have a bowel movement. born.
Your baby is now the size of a banana, weighing about 300 grams.

Thai nhi tuần thứ 20
Thai nhi tuần thứ 20

Week 21


Baby's movements have changed from flapping wings to kicking or kicking the wall of your uterus. You can start paying attention to the poses as you get used to the baby's activities.
Your baby is the size of a carrot, about 360 grams.

Thai nhi tuần thứ 21
Thai nhi tuần thứ 21

22nd week


Our baby now looks like a miniature newborn. Features like lips and eyebrows are more pronounced, but the pigment that would color her eyes hasn't appeared yet.
Your baby weighs 430 grams.

Thai nhi tuần thứ 22
Thai nhi tuần thứ 22

23rd week


Baby's ears are getting better and better at picking up sounds. Even after birth, your baby may recognize some of the noises she now hears inside the uterus.
Your little friend is the size of a large mango, about 500 grams.

Thai nhi tuần thứ 23
Thai nhi tuần thứ 23

24th week


Our little friend has a rather long and thin figure, but the time to be chubby is coming. Your skin is still thin and translucent, but that will start to change soon, too.
Our little friend is as big as a cob of corn, about 600 grams.

Thai nhi tuần thứ 24
Thai nhi tuần thứ 24

Week 25


Baby's wrinkled skin begins to be filled with fat, making him look more like a newborn. Your baby's hair is starting to grow in color and texture.
Your baby now weighs about 660 grams.

Thai nhi tuần thứ 25
Thai nhi tuần thứ 25

26th week


Your baby is now inhaling and exhaling amniotic fluid, which helps with lung development. These breathing movements are the practice for the first breath of air at birth.
Your baby weighs about 760 grams.

Thai nhi tuần thứ 26
Thai nhi tuần thứ 26

27th week


This is the last week of your second trimester of pregnancy. Dear little one now sleeps and wakes up on a regular schedule, and your brain is very active. Your lungs aren't fully formed yet, but they can function outside of the uterus with medical help.
Mom's little friend is about 875 grams.

Thai nhi tuần thứ 27
Thai nhi tuần thứ 27

Third trimester of pregnancy: What's going to happen?


During the third trimester, you may urinate more often or experience leg cramps when your baby presses on nerves in your hips and back.
The honeymoon phase of pregnancy is over and the bliss of parenthood is looming on the horizon. Now is the time to do things like sign up for birthing classes, visit the doctor more often, and create a baby registry.

Thai nhi quý 3 thai kỳ
Thai nhi quý 3 thai kỳ

28th week


Your baby's eyesight is developing, this allows him to perceive light from outside through the filter. She can blink, and your eyelashes are already grown.
Your baby weighs about 1000 grams.

Thai nhi tuần thứ 28
Thai nhi tuần thứ 28

29th week


Your baby's muscles and lungs are busy getting ready for the outside world, and his head is growing to make room for his developing brain.
Your baby is the size of a pumpkin.
From week 29 to week 34, babies gain an average of 200g per week

Thai nhi tuần thứ 29
Thai nhi tuần thứ 29

30th week


Your baby is surrounded by half a liter of amniotic fluid, although the amount of amniotic fluid will become less as he grows and takes up more space inside your uterus.

Thai nhi tuần thứ 30
Thai nhi tuần thứ 30

31st week


Now our little one can wiggle his pretty head. A protective layer of fat is being accumulated under the skin and filling the small arms and legs.

Thai nhi tuần thứ 31
Thai nhi tuần thứ 31

32nd week

Trắc nghiệm: Khi thai nhi 32 tuần, mẹ cần chú ý gì?

Khi bước vào tuần thứ 32 của thai kỳ, thai nhi sẽ có bước phát triển vượt trội và dẫn đến những thay đổi về mọi mặt trong cơ thể mẹ. Vậy hãy cùng tìm hiểu xem khi thai 32 tuần chúng ta cần lưu ý những gì qua bài trắc nghiệm sau đây nhé.

Mom will probably gain half a kilogram every week. Half of that weight goes directly to the little one, who will gain from one-third to one-half of her birth weight over the next seven weeks to prepare for life outside.

Thai nhi tuần thứ 32
Thai nhi tuần thứ 32

33rd week


The baby's skull bones have not yet been fused but are connected by cartilage tissue, which makes it easier for the baby's head to pass through the birth canal, they will not fuse completely until the baby is an adult.

Thai nhi tuần thứ 33
Thai nhi tuần thứ 33

34th week


Your baby's central nervous system and lungs are maturing. Babies born between 34 and 37 weeks with no other health problems can usually live normal long lives.
The average baby weight is about 2100 grams
From week 34 to week 40, your baby's weight increases on average about 200-250 grams per week.

Thai nhi tuần thứ 34
Thai nhi tuần thứ 34

Week 35


This place is getting more and more crowded, mom! Your baby's kidneys are fully developed, and the liver is also able to process some waste products.

Thai nhi tuần thứ 35
Thai nhi tuần thứ 35

36th week


Your little one is gaining about 30 grams per day. You are also losing the smooth membrane that surrounds your body along with the toxins and waxes that have protected you from the beginning until now

Thai nhi tuần thứ 36
Thai nhi tuần thứ 36

37th week


Mom's due date is fast approaching, but even though she looks like a newborn baby, she is not ready to enter the new world. Over the next two weeks, your baby's lungs and brain will fully mature.

Thai nhi tuần thứ 37
Thai nhi tuần thứ 37

Week 38


Are you curious about your baby's eye color? Your baby's irises aren't pigmented yet, so if your baby is born with blue eyes, they'll change color until they're about 1 year old.

Thai nhi tuần thứ 38
Thai nhi tuần thứ 38

Full term pregnancy


At 39 weeks, your baby will be considered full term. In the illustration, you can see how the mucus plug that seals your uterus and internal organs is pinched.

Em bé được coi là đủ tháng khi ở tuần thứ 39
Em bé được coi là đủ tháng khi ở tuần thứ 39

39th week


Baby has fully developed physically, but you are still busy storing fat to help regulate body temperature when going out into the world.

Thai nhi tuần thứ 39
Thai nhi tuần thứ 39

Week 40


If your due date has passed, it will not be as late as you think, especially if you calculate your due date based on the first day of your last period. Sometimes women ovulate later than expected.
But if you don't have any signs of labor on your due date, your doctor will do some tests like ultrasound and non-stress testing to make sure you can continue the pregnancy safely.
The average birth weight of a South Asian infant between 38-40 weeks is about 3200 grams - 3300 grams.

Thai kỳ tuần thứ 40
Thai kỳ tuần thứ 40

Week 41


At present, the mother's pregnancy is called the old-term pregnancy. More than 2 weeks from the due date is creating the risk of complications for mother and baby, the doctor will definitely advise the mother to perform induction.

Thai nhi tuần thứ 41
Thai nhi tuần thứ 41
See fetal development week by week in detail at:

Labor and birth


Seeing your baby for the first time is wonderful, but exactly what will lead to that moment is unpredictable, and it's natural for moms to feel anxious. Please consult your doctor and visit during pregnancy to ensure the health of mother and baby are always best protected.
During pregnancy, the mother may encounter a number of diseases if she does not have a proper diet, rest and regular antenatal check-up: Gestational diabetes, thyroid diseases, pre-eclampsia , high blood pressure,... These are all dangerous diseases and are difficult to detect if not tested and checked for pregnancy health. To protect the health of mother and baby during pregnancy, Vinmec offers all-inclusive Maternity packages.
Mother and baby will receive comprehensive care: before, during and after birth. Mother will be performed health check-ups, especially thyroid screening, Rubella test; Testing for parasites transmitted from mother to child. The baby will be screened before birth and after birth to help screen for abnormal diseases and birth defects right from the womb. In particular, at Vinmec, doctors will analyze the results and provide genetic counseling for prenatal screening for babies.

Khách hàng khám thai tại Vinmec
Khách hàng khám thai tại Vinmec

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