1 month old baby in womb

Fetal Development: Week-by-Week Stages of Pregnancy

Overview

What are the three stages of fetal development called?

Fetal development is an orderly and intricate process. It begins before you even know you’re pregnant and ends with the birth of your baby. Between conception and delivery, there are many detailed steps that have to occur.

There are three stages of fetal development: germinal, embryonic and fetal. Most people don’t talk about their pregnancy in these terms, but it can be helpful to know.

Germinal stage

The germinal stage is the shortest stage of fetal development. It begins at conception when a sperm and egg join in your fallopian tube. The sperm fertilizes the egg and creates a zygote. The zygote begins its journey down to your uterus over the course of about one week. During this journey, the zygote divides many times, eventually creating two separate structures. One structure eventually becomes the embryo (and later, the fetus) and the other becomes the placenta. Cell division continues at a rapid pace. Eventually, the zygote turns into a blastocyst. The blastocyst arrives at your uterus and implants into your uterine lining. If implantation is successful, your body immediately begins producing hormones to support a pregnancy. This also stops your menstrual period.

Embryonic stage

The embryonic stage lasts from about the third week of pregnancy until the eighth week of pregnancy. The blastocyst begins to take on distinct human characteristics. It’s now called an embryo. Structures and organs like the neural tube (which later becomes the brain and spinal cord), head, eyes, mouth and limbs form. The embryo’s heart begins to develop and pulse around the sixth week. Buds that will become arms and legs also form around the sixth week. By the end of the eighth week, most of the embryo’s organs and systems take shape. For a lot of people, this is the point in pregnancy where morning sickness begins.

Fetal stage

The fetal stage of development begins around the ninth week and lasts until birth. This is when the embryo officially turns into a fetus. The fetus gets its assigned sex around nine weeks of pregnancy, although your healthcare provider can’t detect it on ultrasound yet. The fetus’s major organs and body systems continue to grow and mature. Things like fingernails, eyelashes and hair also grow. The fetus is able to move its limbs, although you may not feel it until 20 weeks of pregnancy. The majority of growth — in both weight and length — happens in the fetal stage.

When does a pregnancy start?

The start of pregnancy is actually the first day of your last menstrual period (LMP). This is the gestational age of the fetus. It’s about two weeks ahead of when conception actually occurs. Though it may seem strange, the date of the first day of your last period will be an important date when determining your due date. Your healthcare provider will ask you about this date and will use it to figure out how far along you are in your pregnancy.

How does conception work?

Each month, your body goes through a reproductive cycle that can end in one of two ways. You’ll either have a menstrual period or become pregnant. This cycle is continuously happening during your reproductive years — from starting your period to menopause around age 50.

In a cycle that ends with pregnancy, there are several steps. First, a group of eggs (called oocytes) gets ready to leave your ovary for ovulation (release of the egg). The eggs develop in small, fluid-filled cysts called follicles. Think of these follicles as small containers for each immature egg. Out of this group of eggs, one will become mature and continue through the cycle.

The mature follicle now opens and releases the egg from your ovary. This is ovulation.

After ovulation, the opened follicle develops into a structure called the corpus luteum. This releases the hormones progesterone and estrogen. Progesterone helps prepare your uterine lining for pregnancy. If you don’t become pregnant during a cycle, this lining is what your body sheds during your period. If sperm fertilizes the egg, conception occurs and the fertilized egg begins its journey to your uterus, where it will implant.

How long is a pregnancy?

Traditionally, we think of pregnancy as a nine-month process. However, this isn’t always the case. A full-term pregnancy is 40 weeks, or 280 days. Depending on what months you’re pregnant during (some are shorter and some longer) and what week you deliver, you could be pregnant for either nine months or 10 months. This is completely normal and healthy.

Stages of Growth Month-by-Month in Pregnancy

The fetus will change a lot throughout a typical pregnancy. This time is divided into three stages, called trimesters. Each trimester is a set of about three months. Your healthcare provider will probably talk to you about fetal development in terms of weeks. So, if you’re three months pregnant, you’re about 12 weeks.

You’ll see distinct changes in the fetus, and yourself, during each trimester of pregnancy.

First trimester

The first trimester will span from conception to 12 weeks. This is generally the first three months of pregnancy. During this trimester, the fertilized egg will change from a small grouping of cells to a fetus that begins to have human features. The first trimester is exciting, but also when most people develop unpleasant symptoms like morning sickness and fatigue.

Month 1 (weeks 1 through 4)

Although it’s strange, the first two weeks of pregnancy are a “getting ready” period. Your body slowly releases more hormones and your uterus prepares for a potential pregnancy. At the end of the second week, your ovary releases an egg (ovulation). If sperm meets an egg just after ovulation, the process to pregnancy continues.

• Week 3: Fertilization occurs during the third week. A sperm and egg join and create a zygote.
• Week 4: The tiny bundle of cells turns into a blastocyst and implants into your uterine lining. The beginning of what will become the placenta forms. A water-tight sac forms around the blastocyst. This is the amniotic sac, and it provides cushioning to a fetus during pregnancy.

By the end of the fourth week, the blastocyst is about 2 millimeters (mm) long — the size of a poppy seed.

Month 2 (weeks 5 through 8)

The second month of pregnancy is when most people realize they’re pregnant. Pregnancy hormones go into overdrive, and by about the fifth week, an at-home pregnancy test will show as positive. This is when many people begin to feel symptoms of pregnancy.

• Week 5: The neural tube (brain, spinal cord and other neural tissue of the central nervous system) forms. The tiny “heart” tube will beat 110 times a minute by the end of the fifth week.
• Week 6: Tiny buds that become arms and legs also develop. Blood cells are taking shape, and circulation will begin. Structures that’ll become the ears, eyes and mouth take form. Your healthcare provider can probably detect a heartbeat on a vaginal ultrasound.
• Week 7: Bones begin replacing soft cartilage and genitals begin to form. The embryo’s head is large in proportion to the rest of its body. Some people think the embryo resembles a small tadpole or seahorse due to its prominent tail (which becomes legs) and large head.
• Week 8: All of the major organs and body systems are developing. The fetus has web-like hands and feet. Eyes become visible and ears begin to form. The umbilical cord is fully developed and helps to transport oxygen and blood to the embryo.

After the 8th week, healthcare providers refer to the embryo as a fetus. It will remain a fetus until birth.

By the end of the second month, the fetus is about 0.5 to 1 inch (in) long — about the size of a black bean.

Month 3 (weeks 9 through 12)

The third month of pregnancy is when an embryo becomes a fetus. It’s a period of rapid growth and development. The fetus develops distinct facial features, limbs, organs, bones and muscles. By the end of the 12th week, the fetus has an assigned sex, but it won’t be visible on ultrasound for several more weeks.

• Week 9: The beginnings of teeth and taste buds are forming. Its muscles are forming and its body shape takes on more of a human appearance. But, its head is still 50% of its length. Your provider may be able to hear its heartbeat with a Doppler ultrasound.
• Week 10: The arms, hands, fingers, feet and toes are fully formed (no more webbed fingers). Fingernails and toenails are beginning to develop and the external ears form. The external genitals also begin to form, but it’s too soon to see them on an ultrasound.
• Week 11: The fetus is starting to explore a bit by doing things like opening and closing its fists and mouth. Its knees, elbows and ankles are working, but it’s too soon to feel any kicks. The bones are hardening, but its skin is still see-through. Facial features are more prominent.
• Week 12: All the organs, limbs, bones and muscles are present and will continue to develop in order to become fully functional. The circulatory, digestive and urinary systems are also working and the liver produces bile. The fetus is drinking and peeing amniotic fluid.

Since the most critical development has taken place, your chance of miscarriage drops considerably after 12 weeks (the end of the first trimester). Most people begin feeling some relief from morning sickness now, too.

At the end of the third month, the fetus is about 2.5 to 3 inches long — about the size of a plum.

Second trimester

The second trimester of pregnancy is often thought of as the best part of the experience. By this time, any morning sickness is probably gone and the discomfort of early pregnancy has faded. You may also start to feel movement as the fetus flips and turns in your uterus. During this trimester, many people find out about the fetus’s assigned sex. This is typically done during an anatomy scan (an ultrasound that checks physical development) at around 20 weeks.

Month 4 (weeks 13 through 16)

Many people begin showing signs of being pregnant at this point in pregnancy, especially if you’ve been pregnant before. Your pregnancy care provider can hear the fetal heartbeat loud and clear on a Doppler ultrasound. The fetus can even suck its thumb, yawn, stretch and make faces.

• Week 13: Vocal cords form and the fetus’s large head begins to grow proportionate to its body.
• Week 14: The fetus’s skin starts to thicken and fine hair begins to grow. It can start bringing its fingers to its mouth and turn its head. External genitals are fully developed and fingerprints begin to form.
• Week 15: Some organs, like intestines and ears, are moving to their permanent location. The fetus still uses amniotic fluid to practice breathing, but its lungs are beginning to develop. The fetus begins to make more purposeful movements, like sucking its thumb or smiling.
• Week 16: The fetus has lips and its ears are developed enough that it can hear you talk. Even though its eyes are closed, the fetus can react to light by turning away from it.

By the end of the fourth month, the fetus is about 5 inches long and weighs about 4 ounces. For reference, that’s about as big as an avocado.

Month 5 (weeks 17 through 20)

By the end of the fifth month of pregnancy, most people begin to feel the fetus moving around. The first movements are called quickening and can feel like a flutter. If your pregnancy has been healthy to this point, you’ll finally get your first ultrasound. You may even get to find out the fetus’s assigned sex.

• Week 17: The fetus still has thin skin, but will start to put on fat. Its skin is covered with a whitish coating called vernix. This “cheesy” substance is thought to protect fetal skin from long-term exposure to amniotic fluid.
• Week 18: The fetus is covered in lanugo, a peach fuzz-like hair. It helps keep the fetus warm and provides another layer of protection. The fetus may have a sleep-wake cycle, and loud noises may wake the fetus if it’s asleep.
• Week 19: The fetus is getting stronger and most people begin to feel kicks and punches. The fetus also has its own unique set of fingerprints and can hiccup.
• Week 20: The fetus’s nails grow towards the end of its fingers. The area of the brain responsible for its five senses begins to develop.

By the end of the fifth month, the fetus is about 9 to 10 inches long and weighs about 1 pound.

Month 6 (weeks 21 through 24)

If you could look inside your uterus right now, you’d see that the fetus’s skin is reddish in color, wrinkled and veins are visible through translucent skin. In the sixth month of pregnancy, its eyelids begin to part and you may notice regular, jerky movements. The fetus responds to sounds by moving or increasing its pulse.

• Week 21: Limb movements are coordinated and frequent. The fetus has bone marrow that helps it produce blood cells.
• Week 22: The fetus’s grasp is getting stronger and it can touch its ears and the umbilical cord. It can hear your heartbeat, your stomach rumble and your breathing.
• Week 23: If born prematurely, the fetus may survive after the 23rd week with intensive care. It will begin rapidly adding fat to its body.
• Week 24: The fetus’s lungs are fully developed, but not well enough to work outside your uterus.

By the end of the sixth month, the fetus is about 12 inches long and weighs about 2 pounds.

Month 7 (weeks 25 through 28)

The fetus continues to mature and develop reserves of body fat. The fetus changes position frequently and responds to stimuli, including sound, pain and light. The amniotic fluid begins to diminish.

• Week 25: More body fat makes the fetus’s skin less wrinkled and plumper. Its nervous system is quickly maturing.
• Week 26: The fetus makes melanin, the substance that gives skin and eyes their color. The fetus’s lungs start to make surfactant, a substance that helps it breathe after birth.
• Week 27: The fetus can open its eyes and blink. It also has eyelashes.
• Week 28: The fetus may begin turning head-down in your uterus as it gets ready for birth. At the end of the seventh month, the fetus is about 14 to 15 inches long and weighs between 2 and 3 pounds.

Third trimester

This is the final part of your pregnancy. You may be tempted to start counting down the days to your due date and hope that it comes early, but each week of this final stage of development helps the fetus prepare for birth. Throughout the third trimester, the fetus gains weight quickly, adding body fat that’ll help after birth.

Your healthcare provider will monitor you closely as you approach your due date. You’ll visit your provider biweekly and then weekly. Make sure to ask your provider any questions you have about labor and delivery.

Month 8 (weeks 29 through 32)

The fetus continues to mature and develop reserves of body fat. The brain develops most rapidly during this time. The fetus can see and hear most stimuli. Most internal systems are well-developed, but the lungs may still be immature.

• Week 29: You may notice the kicks and jabs feel more like pokes now that the fetus is getting cramped in the amniotic sac.
• Week 30: The fetus can control its own body heat. Its brain is maturing and growing rapidly.
• Week 31: The fetus can process more information and stimuli. You can probably notice more distinct patterns in when it’s awake and when it’s asleep.
• Week 32: The fetus’s skin isn’t translucent anymore. Other than the lungs and brain, most other organs are well-formed and ready for birth.

The fetus is about 17 to 18 inches long and weighs as much as 5 pounds.

Month 9 (weeks 33 through 36)

During this stage, the fetus continues to grow and mature. The lungs are close to being fully developed at this point in pregnancy. The ninth month is mostly about putting the finishing touch on growth and brain development.

• Week 33: The fetus’s bones are hardening, with exception of its brain, which needs to be soft to descend the birth canal.
• Week 34: The vernix that protects the fetus’s skin starts to get thicker.
• Week 35: The fetus’s brain continues to grow, but still only weighs two-thirds of what it should at birth.
• Week 36: The fetus loses its lanugo and it has hair on its head.

The fetus is about 17 to 19 inches long and weighs from 6 to 7 pounds.

Month 10 (Weeks 37 through 40)

In this final month, you could go into labor at any time. At this point, the fetus’s position may have changed to prepare for birth. Ideally, it’s head-down in your uterus. You may feel very uncomfortable in this final stretch of time as the fetus drops down into your pelvis and prepares for birth. Your provider may encourage you to perform kick counts, which is a way to track how much the fetus moves.

• Week 37: The fetus’s toenails reach the end of its toes. You may start to feel the fetus drop into your pelvis.
• Week 38: The fetus is packing on 0.5 pounds per week to get to its final size.
• Week 39: The fetus is full-term and ready to meet the world!
• Week 40: It’s your due date week. Call your pregnancy care provider if you notice any signs of labor.

The fetus is about 18 to 20 inches long and weighs about 7 to 9 pounds.

Frequently Asked Questions

How early can I know I’m pregnant?

From the moment of conception, the hormone human chorionic gonadotrophin (HCG) will be present in your blood. This hormone is created by the cells that form the placenta (food source for the growing fetus). It’s also the hormone detected in a pregnancy test. Even though this hormone is there from the beginning, it takes time for it to build within your body. It typically takes three to four weeks from the first day of your last period for the HCG to increase enough to be detected by pregnancy tests.

When should I reach out to my healthcare provider about a new pregnancy?

Most healthcare providers will have you wait to come in for an appointment until you’ve had a positive home pregnancy test. These tests are very accurate once you have enough HCG circulating throughout your body. This can be a few weeks after conception. It’s best to call your healthcare provider once you have a positive pregnancy test to schedule your first appointment.

When you call, your healthcare provider may ask you if you’re taking a prenatal vitamin. These supplements contain folic acid. It’s important that you get at least 400 mcg of folic acid each day during pregnancy to make sure the fetus’s neural tube (beginning of the brain and spine) develops correctly. Many healthcare providers suggest that you take prenatal vitamins with folic acid even when you aren’t pregnant. If you weren’t taking prenatal vitamins before your pregnancy, your provider may ask you to start as soon as possible.

What weeks are most important for fetal development?

Each trimester or phase of pregnancy carries its own unique risks. It’s hard to pinpoint specific weeks as being more or less important. However, most healthcare providers will say the most important time for fetal development is the first 13 weeks of the pregnancy (or the first trimester). The risk of miscarriage drops after the first trimester, when the fetus’s major organs and systems are formed and working. This isn’t to say that your pregnancy becomes less important after 13 weeks. It just means a lot of the critical steps and processes are complete and that a lot of the most major birth disorders occur in the first trimester.

What does full-term mean in a pregnancy?

Once you get close to the end of your pregnancy, healthcare providers may use several terms to describe when you go into labor. These terms are labels that divide up the last few weeks of pregnancy.

They’re helpful in determining how likely a baby is to have complications at birth. For example, babies that are born in the early term period (or before it) generally have a higher risk of breathing issues than babies born at full term.

When you’re looking at these labels, it’s important to know how they’re written. You may see the week first (38) and then two numbers separated by a slash mark (6/7). This stands for how many days you currently are in the gestational week. So, if you see 38 6/7, it means that you’re on day 6 of your 38th week.

The last few weeks of pregnancy are divided into the following groups:

• Early-term: 37 0/7 weeks through 38 6/7 weeks.
• Full-term: 39 0/7 weeks through 40 6/7 weeks.
• Late-term: 41 0/7 weeks through 41 6/7 weeks.
• Post-term: 42 0/7 weeks and on.

Talk to your healthcare provider about any questions you may have about gestational age and due date.

A note from Cleveland Clinic

There’s a lot that needs to happen for a pregnancy to occur, grow and result in a birth. Learning about how the fetus grows can be exciting and eye-opening, especially when you realize how many organs, systems and body functions develop within a nine-month period. Both you and the fetus growing inside of you go through many changes during pregnancy. Ask your pregnancy care provider about these changes and any other questions you have. They’re there to be a resource to you and give you the best possible care.

Pictures of Fetal Development Month-by-Month

Reviewed by Traci C. Johnson, MD on February 20, 2023

You're pregnant. Congratulations! Are you curious how big your developing baby is, what your baby looks like as it grows inside you, and when you'll feel it move? Take a peek inside the womb to see how a baby develops from month to month.

Fertilization happens when a sperm meets and penetrates an egg. It's also called conception. At this moment, the genetic makeup is complete, including the sex of the baby. Within about three days after conception, the fertilized egg is dividing very fast into many cells. It passes through the fallopian tube into the uterus, where it attaches to the uterine wall. The placenta, which will nourish the baby, also starts to form.

At this point the baby is developing the structures that will eventually form their face and neck. The heart and blood vessels continue to develop. And the lungs, stomach, and liver start to develop. A home pregnancy test would show positive.

The baby is now a little over half an inch in size. Eyelids and ears are forming, and you can see the tip of the nose. The arms and legs are well formed. The fingers and toes grow longer and more distinct.

The baby measures about 2 inches and starts to make its own movements. You may start to feel the top of your uterus above your pubic bone. Your doctor may hear the baby's heartbeat with special instruments. The sex organs of the baby should start to become clear.

The baby now measures about 4.3 to 4.6 inches and weighs about 3.5 ounces. You should be able to feel the top of your uterus about 3 inches below your belly button.  The baby's eyes can blink and the heart and blood vessels are fully formed. The baby's fingers and toes have fingerprints.

The baby weighs about 10 ounces and is a little more than 6 inches long. Your uterus should be at the level of your belly button. The baby can suck a thumb, yawn, stretch, and make faces. Soon -- if you haven't already -- you'll feel your baby move, which is called "quickening."

An ultrasound is usually done for all pregnant women at 20 weeks. During this ultrasound, the doctor will make sure that the placenta is healthy and attached normally and that your baby is growing properly. You can see the baby's heartbeat and movement of its body, arms, and legs on the ultrasound. You can usually find out whether it's a boy or a girl at 20 weeks.

Shown here is a 2D ultrasound (inset) contrasted with a 4D ultrasound, both at 20 weeks.

The baby weighs about 1.4 pounds now and responds to sounds by moving or increasing their pulse. You may notice jerking motions if they hiccup. With the inner ear fully developed, the baby may be able to sense being upside down in the womb.

The baby weighs about 2 pounds, 6 ounces, and changes position often at this point in pregnancy. If you had to deliver prematurely now, there is a good chance the baby would survive. Ask your doctor about preterm labor warning signs. Now is the time to register for birthing classes. Birthing classes prepare you for many aspects of childbirth, including labor and delivery and taking care of your newborn.   

The baby weighs almost 4 pounds and is moving around often. The baby's skin has fewer wrinkles as a layer of fat starts to form under the skin. Between now and delivery, your baby will gain up to half their birth weight. Ask your doctor how to do a fetal movement chart. Think about breastfeeding. You may notice a yellowish fluid leaking from your breasts. That is colostrum, and it happens to get your breasts ready for making milk. Most women go to the doctor every two weeks at this stage of pregnancy.

Babies differ in size, depending on many factors, such as gender, the number of babies being carried, and size of the parents. So your baby's overall rate of growth is as important as the actual size. On average, a baby at this stage is about 18.5 inches and weighs close to 6 pounds. The brain has been developing rapidly. Lungs are nearly fully developed. The head is usually positioned down into the pelvis by now. Your baby is considered at 'term' when they are 37 weeks. They are an early term baby if born between 37-39 weeks, at term, if they're 39-40 weeks and late term if they're 41-42 weeks.

A mother's due date marks the end of their 40th week. The delivery date is calculated using the first day of their last period. Based on this, pregnancy can last between 38 and 42 weeks with a full-term delivery happening around 40 weeks. Some post-term pregnancies -- those lasting more than 42 weeks -- are not really late. The due date may just not be accurate. For safety reasons, most babies are delivered by 42 weeks. Sometimes the doctor may need to induce labor.

IMAGES PROVIDED BY:

(1) Copyright © LookatSciences / Phototake – All rights reserved.
(2) Dr. David M. Phillips / Visuals Unlimited / Getty Images
(3) 3D4Medical.com / Getty Images
(4) Copyright © Scott Camazine / Phototake -- All rights reserved.
(5) Copyright © LookatSciences / Phototake – All rights reserved.
(6) Nestle / Petit Format / Photo Researchers, Inc.
(7) © Lennart Nilsson Photography AB. All rights reserved worldwide.
(8) a) Dr.Benoit/Mona Lisa. Copyright © LookatSciences / Phototake -- All rights reserved. b)Vincenzo Lombardo / Photographer's Choice / Getty Images
(9) Dr. Benoit/Mona Lisa. Copyright © LookatSciences / Phototake -- All rights reserved.
(10) © Lennart Nilsson Photography AB. All rights reserved worldwide.
(11) Jose Manuel Gelpi Diaz / iStockphoto
(12) © Lennart Nilsson Photography AB. All rights reserved worldwide.
(13) © Yoav Levy / Phototake -- All rights reserved.

SOURCES:

American Academy of Family Physicians.

American College of Obstetricians and Gynecologists: "How Your Baby Grows During Pregnancy."

KidsHealth.org: "Pregnancy Calendar."

March of Dimes: "Prenatal Care – Ultrasound."

US Department of Health and Human Services Office of Women’s Health: "Pregnancy: Breast Changes."

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What does a child do while it is in the mother’s stomach

August 17, 2018

In 9 months, a child goes a long way from a tiny embryo to a chubby baby and already in the womb acquires some features that will remain with him for life: for example, you can understand whether he will become right-handed or left-handed and what kind of food he will prefer. In a fairly short period of time, a lot of interesting things happen to a child, and today we invite you to go through the path from birth to birth with your baby.

1st trimester of pregnancy
1st–2nd week

So the long journey began. For the first 4 days, the future person is smaller than a grain of salt - its size is only 0.14 mm. However, starting from the 5th day, it begins to grow and by the 6th it almost doubles - up to as much as 0.2 mm. On the 4th day, the embryo "comes" to where it will spend the next 9 months - into the uterus, and on the 8th day it is implanted in its wall.

3rd–4th week

© EDITORIAL USE ONLY/East News

Embryo at the 4th week of pregnancy.

Around the 20th day of pregnancy, a very important event occurs: the neural tube appears, which will then turn into the spinal cord and brain of the child. Already on the 21st day, his heart begins to beat and all important organs, such as the kidneys and liver, begin to form. The eyes have not yet taken their usual position - the bubbles from which they will then take shape are located on the sides of the head. By the end of the 1st month, the embryo has a circulatory system, and the spine and muscles begin to develop.

5th–6th week

© EDITORIAL USE ONLY/East News © lunar caustic/wikimedia

At the 5th week, the hands appear in the embryo, however, the fingers are still very difficult to distinguish, but in the joints the arms and legs are already bent. It was at this time that the external genitalia begin to form, but it is not yet possible to see on an ultrasound whether it is a boy or a girl. By the way, since its appearance, the embryo has grown a lot - it has increased by as much as 10 thousand times. Already now, the baby's face is beginning to form, and the eyes, which will be closed for a very long time, darken, becoming more human-like.

7th–8th week

The 7th week of pregnancy is the time when the baby begins to move, however, so far completely unnoticed by the mother, and the fingers and toes become almost the same as in adults. At this stage, the rudiments of milk teeth appear in the embryo and the reproductive system develops, and the kidneys begin to produce urine. Despite the fact that the growth of the fetus is only 2.5 cm, it acquires its own facial expressions, it has eyelids, and the tip of the nose becomes more defined.

9th–10th week

© lunarcaustic/wikimedia

Baby at 9-10 weeks of gestation.

By this time, the baby has already grown well - its weight is 4 grams, and its height is 2-3 cm. Despite its tiny size, the brain is already divided into two hemispheres, and milk teeth and taste buds are beginning to form. The baby's tail and membranes between the fingers on the hands disappear, he begins to swim in the amniotic fluid and move even more actively, although still unnoticed by the mother. It was at this time that the child's individual facial features appear, and hair begins to grow on the head.

11–12 weeks

At this time, the genital organs are formed in the child, so it is already possible to find out his sex on an ultrasound scan, although the probability of an error is still high. The child still looks a little alien: he has a big head and a small body, but his face is more and more like an adult. The ears are almost in the right position, eyebrows and eyelashes appear. The cartilage that makes up the skeleton gradually ossifies, new blood vessels appear, and hormone production begins. By the way, the baby has already grown up to 6 cm and weighs about 20 grams.

13th-14th week

Baby at 14 weeks pregnant.

Despite the fact that the child's head is half the length of the entire body, the face is more and more reminiscent of an adult, and the rudiments of all 20 milk teeth have already been formed in the oral cavity. The child is already able to put his finger in his mouth, but he will learn to suck a little later. Due to the active formation of blood vessels, the baby's skin is red and very thin, so vellus hair appears on the body - lanugo, which is necessary to maintain a special lubricant that protects against hypothermia.

2nd trimester of pregnancy
15th–16th week

By the 15th week, the baby has grown to 10 cm and is gaining weight - now he weighs about 70 grams. Despite the fact that the eyes are still quite low, the face is already quite recognizable, moreover, the child begins to “make faces”, since the facial muscles are well developed. By this time, he already knows how to suck his thumb, and the sebaceous and sweat glands begin their work.

17th–18th week

And finally, the child's auditory canals are formed, so he begins to distinguish sounds well and hears the mother's voice, moreover, he is able to recognize it. In addition to the milk teeth, the embryos of the molars also appear, the bones are finally formed and begin to harden. By the way, the bones of the skull will remain mobile until birth - when passing through the birth canal, they will overlap each other to make it easier for the baby to be born. But the mother is finally beginning to feel the movements of the child, who has grown to 14 cm and 190 grams.

19th-20th week

Baby at 20 weeks pregnant.

Despite the fact that the child's eyes are still closed, he is already well oriented in the surrounding space. Moreover, now you can understand whether the child will be right-handed or left-handed, because right now he begins to use his dominant hand more actively. Fingerprints appear on the baby's fingers - another unique sign of each of us. By the way, the child is already beginning to gradually distinguish day from night and is active at a certain time.

21–22 weeks

The 21st week is the time when the baby begins to gain weight due to the formation of subcutaneous fat. Soon, the folds that newborns have will appear on his arms and legs. On the 22nd week, those neurons are formed in the brain that will be with a person all his life. Very soon the child will open his eyes, he is already trying to do this, and the eyeballs move almost like an adult.

23–24 weeks

At 23 weeks, the baby may begin to dream, and his face is so formed that an ultrasound can determine whose facial features he has inherited. His skin becomes opaque, his eyes open, and the child can already react to light, moreover, bright flashes can scare him. By the 24th week, the baby grows to almost 30 cm, and its weight reaches 0.5 kg.

25th–26th week

At this time, the taste buds of the child are finally formed and, tasting the amniotic fluid, he can frown if he does not like it. By the way, this is how eating habits are formed - already in the womb we have our favorite and unloved foods. Very soon the child will learn to blink and can already see a little, however, so far it is very, very vague.

3rd trimester of pregnancy
27th–28th week

Baby at 27–28 weeks of gestation.

If you do an ultrasound at this time, you can see how the baby smiles and intensively sucks his thumb. At this time, the baby has the first "toy" - his own umbilical cord, and he actively studies his body. At the end of the 7th month of pregnancy, the child develops an individual metabolism, which he will have all his life. The baby is already quite large - his weight reaches 1.2 kg, and his height is 35 cm.

29th-30th week

© East News

Baby at 30 weeks pregnant.

The layer of subcutaneous fat is increasing, and the baby is becoming more and more plump and well-fed. In addition, he already knows how to cry, cough, and even sometimes hiccups - this happens, most likely, when he swallows too much amniotic fluid. By the 30th week, the baby's brain is already so developed that it is quite capable of remembering and even analyzing information.

31–32 weeks

At this time, a person has all 5 senses, and his daily routine is more and more reminiscent of the one he will follow after birth. The child hears the work of all the organs of the mother, knows her voice perfectly, thanks to which, immediately after birth, he is able to distinguish her from all other people. The baby's immune system begins to produce antibodies that will protect him from all kinds of infections that may lie in wait in the first days and months after birth.

33–34th week

And finally, subcutaneous fat is already formed, and lanugo disappears from the body of the fetus. By this time, the baby has grown a lot - the length of his body reaches 40 cm, and the weight is very close to or even exceeds 2 kg. The baby's nervous system is already fully formed, but the lungs are still developing.

35th–36th week

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The child yawns. 3D ultrasound at 36 weeks pregnant.

At this time, the child looks almost exactly the same as when he was born. He is still quite thin, but the layer of subcutaneous fat is increasing more and more intensively. However, his hair and nails are already fully developed, and he himself becomes so big that he has almost no room to maneuver, so he can move less than in earlier stages.

37–38th week

And finally, the process of forming a person has finally ended - now he is completely ready for birth, and obstetricians consider the pregnancy to be full-term. Lanugo completely disappears from his body and can only sometimes remain on his arms and legs. Since there is almost no space left in the uterus, it may seem to the mother that the child has begun to move more intensively, but in fact the force of the blows has increased, because the child's muscles have already completely formed and strengthened.

39th–40th week

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The first minutes after birth.

The lungs of a child continue to form until the very birth, and only at the time of birth they release the right amount of surfactant - a substance that prevents the alveoli from sticking together after the first independent breath. Very soon, the baby will announce its birth with the first cry and begin its long journey through a large and interesting world.

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Child development by weeks | 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 is determined, you can distinguish the mouth, nose, auricles. 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 area (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.

Fetal development by weeks 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 amniotic sac 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".

fetal development: 11–14 weeks

The development of the fetus in the photo of the legs: Week 11