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Pregnancy is the most ecstatic time for a woman, but, it comes with a lot of anxiety and worry. While weight gain and physical changes hold a fair share of this agony, constant concern for the baby’s growth and development doesn’t fall quite behind.

Whether you are in the first trimester of pregnancy or are advancing towards the end of your term, your baby is constantly growing. Initially, this growth is pretty basic. Your baby takes a tadpole-like form and slowly develops major organs including the heart and the brain. Gradually, these features advance and your baby gets a pair of eyebrows and grows toenails. During the last months, there is a major increase in the size and weight of the baby as most of the development has already occurred.

If you are excited to know how your baby is forming within your uterus each day and want to know about its development, movements and growth, this article is for you. It will allow you to have a virtual view of the month by month and week by week growth of your baby. Because you can’t get an ultrasound each time you wonder about this, right?

  1. Foetal development month by month
  2. Foetal development week by week
  3. Foetal development video

You now have a vague idea of your baby development, which progresses each week until it is born. Let’s now have a detailed look at the monthly progress of your baby's development along with its size and movements.

4th month pregnancy baby development

By the fourth month of pregnancy, the major organs have already formed but the baby continues to grow in size. It grows doubly during this month from 7 centimetres to 14. The eyelids still remain fused and the eyebrows and eyelashes begin to form as the baby grows some hair. This month witnesses three major events, the first being that the appearance of a larger head and a smaller body diminishes as the body of the foetus grows. Second, the foetal heart sound can now be heard with the help of an ultrasound scanner. Excited, aren’t you? Hold on, there is more. Your baby also begins to move starting this month and if you are lucky enough, you may feel some of these. These movements are quite minute and often involve thumb sucking, which may be negligible in terms of a movement but makes for an essential life skill. Not just this, your baby may even get hiccups and develop a faint cry during this month.

5th month pregnancy foetal growth and development

In the fifth month of pregnancy, 6 to 8 inches long foetus, weighing about 360 grams, is going through a lot of physical changes. The skin of the foetus gets coated with a thick, creamy layer called vernix, which protects it from the amniotic fluid surrounding it. The muscles and bones continue to develop and it has well-defined arms, hands, nails, fingers, eyelids, eyebrows, eyelashes and has fine hair. The movements of the baby continue to enhance and it can now yawn and stretch, in addition to sucking its thumb. It may also be able to open its eyes at times, which means that the eyelids, which were completely shut till now, begin to be functional.

Another peculiar movement you may feel during the 5th month is the much-awaited baby kick and turns. The baby starts developing other important functions like cognitive skills and an improved immune functioning. It also follows a proper sleep-wake schedule now. However, this may be different from your sleep cycle, which is likely to disturb your sleep. The foetus also begins to develop its unique set of fingerprints during this month.

6th month pregnancy foetal size and development

During the sixth month of pregnancy, the foetus immensely increases in size and moves more often. This may be the first time you feel the foetus moving and may experience around 8 to 10 movements every day. This is a sign that your foetus is healthily developing. It now weighs half a kilogram and is 8 to 10 inches in size, which means that it has a fair chance of survival if it is delivered prematurely during this month but that sure has a high risk of disabilities.

The major features of the baby are well-developed by now and it continues to improve the finer features and grows in size during this month, which finally makes it larger than the size of the placenta. Its skin is covered by a layer of fine hair called lanugo, which helps to keep it warm. The ears of the baby are developed and it can probably hear outside sounds. So, you can carry on with your baby talk from now on.

The bones of the foetus are continuing to develop and also start taking a proper form to ascertain an upright posture post birth.

7th month pregnancy foetal movements and growth

Your baby is growing really quick now. It already weighs a kilogram and is 10 to 13 inches in size. Explains much of the weight gain? Rapid growth, development and organisation of the foetus occurs during this month. The organs and systems, which were formed initially, continue to refine during this month but your baby is still covered by the vernix. Fingerprints and even footprints form well and the brain continues to grow and differentiate with an increase in its surface area. This initiates the development of osseous growth points in the skull, which is required for bone expansion post birth.

Not just the brain, its lungs also continue to grow and branch profoundly, improving the chances of premature survival to almost 85%. As your baby grows in size, the space inside your womb seems limited. So, adjusting movements are more than the previous months. As the baby rolls, turns, twists and swishes, you may feel at least 3 movements in half an hour, which indicates that it is quite healthy and active. It may also respond to certain sounds and sensations now.

(Read more: Pregnancy month 7 baby movements)

8th month pregnancy foetal position and development

A major development that occurs during the 8th month of pregnancy is the change in foetal position. It moves around and adapts to a cephalic position by fixing its head between the pelvic bones. This aids in a normal delivery and the foetus stays in this position till then. This also prevents it from swimming around in the amniotic fluid.

Talking of amniotic fluid, it can be seen that its levels diminish during this month, which is an indication of the optimal functioning of its kidneys. Neuronal connections continue to improve and in addition to sound, the foetus may also be able to perceive light.

And it obviously also increases in size. It weighs up to 2.1 kilograms by now and 45 cm in length, which is quite close to its delivery size. The thin layer of hair covering the foetus’s body now sheds as it prepares itself to be born and its external genitalia also develops well. Displacement of testicles and development of vulva occurs in male and female foetuses respectively. The baby has a very high chance of survival if delivered now, but, it may require to spend a few days under intensive care.

9th month pregnancy foetal weight and development

During the ninth month of pregnancy, the baby is well-developed and is just waiting to be born. If it has been given the right nutrition till now, it will attain a size of about 51 centimetres and can weigh up to 3.3 kilograms. Since the baby enormously grows in size, it has lesser space to move around. So, you may experience lesser kicks and rolls now but this is not at all a matter of concern. The layer of vernix covering its skin thickens as the baby begins to descend to a lower position in your womb. This, and the cephalic head positioning of the baby, will assist the process of delivery, which will occur anytime soon. Although the baby delivered during this month will still be considered as preterm, it holds an excellent chance of survival but would need medical attention for quite some time.

1st month pregnancy baby growth

During the first month of pregnancy, your gestation journey begins when the male and female gametes unite to form a zygote. This occurs at the end of the fallopian tube and it is slowly transported down the fallopian tube into the uterus. While it moves, the zygote slowly differentiates to form a blastocyst. The inner layer of this blastocyst will grow to form the foetus and the outer layer will form its protective coverings.

Upon reaching the uterus, the blastocyst strongly embeds within the uterine wall, which is responsible for its nourishment until the placenta is formed. Zygote formed during the first month may be tiny but it contains all the genetic information which is required to form a baby. This is encrypted in the form of a DNA and is inherited equally from both the parents.

2nd month pregnancy foetal growth

The second month marks the beginning of the embryonic stage of the baby, which was yet just a blastocyst. Slowly, the embryo begins to differentiate to be able to form the basic structures. This process of differentiation allows the embryo to form various types of cells including nerve cells, blood cells, and cells of the kidney and the brain. During this month, the embryo grows in size from 2 mm to a whopping 10 mm, which is how you can predict the rate of differentiation.

You may note that at this point your baby is at a high risk of malformation or defects due to maternal habits like smoking, alcohol or certain infections and medications. So, it is very important to take care of these factors.

As the second month advances, the major organs including the brain and the heart begin to develop. Neural tube forms the core for the development of the brain and spinal cord of the baby, which will start this month and continues until the later months of pregnancy. The lungs and gastrointestinal organs start to differentiate and the heartbeat begins to form. Signs of limbs may be seen in the form of tiny buds and eyes may start forming. During this month, the baby starts to curve within your uterus and takes a tadpole-like form with a head and a tail. The growth is often disproportional and is more within the head area giving the look of a large forehead.

(Read more: 2 months pregnant baby size)

3rd month pregnancy foetal development

As the third month begins, the embryo loses its ‘tail’ with the formation of the tailbone at the end of the spine. The eyes form and move from the side of the head towards the front of the face and even begin to develop some pigment responsible for its colour. However, the eyes are shut. Other facial features, especially the ear begin to develop and refine during this month along with the development of the digestive system and the intestines.

The baby is 2.5 inches at the beginning of this month, grows another inch by its end and weighs 43 gram. As this growth occurs, the baby acquires a more human form and the limbs, which were mere buds, begin to grow, marking the formation of arms and elbows. The embryo even begins to grow nails and it is officially termed as a foetus at the end of 10 weeks. Sexual organs also begin to differentiate and the genitals form. It still has a large head, though, it can form some RBCs and by now has tooth buds, taste buds and a palate.

(Read more: Pregnancy month 3)

Isn’t it amazing how a single-celled zygote transforms itself into a baby in just a few months? In fact, it is growing every moment. From becoming a blastocyst to an embryo and then a foetus, your baby undergoes a lot of changes, which are evident each week. Let’s have a look at these developments:

Week Baby growth and development
Week 1     This is actually your menstrual week. The duration of pregnancy is calculated from the first day of your previous cycle. So, fertilisation has not yet occurred.
Week 2  Ovulation occurs during this week, which may be accompanied by mild bleeding or spotting. This releases your egg and makes it available for fertilisation by the male gamete. 
Week 3 Fertilisation occurs now as the male and female gametes unite to form a zygote at the end of fallopian tube. 30 hours after this, it divides to form a two-celled structure. 3 days later, the zygote forms a 16-celled structure, called a morula.
Week 4

The morula then begins to move from the end of the fallopian tube to the uterus, where it gets implanted. It buries itself into the thick lining of the uterine wall (endometrium) and is now called a blastocyst.

The cells then begin to divide rapidly and your baby is about the size of a grain of rice.

Week 5

The neural tube evolves, which will later develop the brain and the spinal cord.

The heart and its circulation begin to form and you miss your period and run a positive pregnancy test due to the hormones released by the developing baby.

Week 6

The baby is now called an embryo and is 3 mm in length. The head and the upper part of the body develop and the heart acquires a tubular shape.

At this stage, the embryo curls up in the uterus and acquires a tadpole-like form.

Eyes may begin to form and buds for the development of limbs appear.

Neural tube slowly starts to develop the brain and the spinal cord.

Week 7

The tubular-shaped heart develops a heartbeat. Amniotic sac and placenta start developing for protection and nutrition respectively.

Slowly, the placenta buries itself into the uterine wall in order to derive nutrition and oxygen.

Week 8

The heart differentiates and forms its chambers. The well-formed 4 chambers start to develop their function. The circulation is still derived through the umbilical cord.

Vertebral column begins to develop but comprises of cartilage instead of bone.

Nervous system continues to develop and electrical activity begins.

Fingers of the embryo start to form. At 8 weeks, the head of the embryo is disproportionately large and the forming spinal cord looks like a tail. Embryo is 1.3 cm in length.

Week 9

Mouth and tongue start forming along with the development of the eyes.

The muscles of the embryo begin to develop, which assists its movements.

RBCs are being produced.

Week10  

Marking a transition, the embryo is now called a foetus and loses its tail. The head is still large but it evolves to a more human-like form. Arms, legs, fingers and toes are distinctly visible now along with the formation of eyelids.

Bony cells replace the cartilage. The foetus is 2.5 cm in length.

Week 11 Heart begins to differentiate and tooth buds develop inside the gums.
Week 12 The eyelids are fused and already formed web-like fingers start developing nails. The foetus begins to move about a bit and its heartbeat can be felt by foetal ultrasound.
Week 13 7 cm in length, the foetus swims around vigorously within the protective sac.
Week 14 The toes also start developing nails now. Swallowing functions evolve and the kidneys are able to synthesise urine. The foetus is 3.5 inches long and its arms are now in proportion to the body. It begins to develop a sleep-wake routine of its own.
Week 15 The fingers and toes continue to grow nails.
Week 16 Sex can be determined by now and the body of the foetus is covered by a protective layer of hair called lanugo. The head starts to become erect and taste buds develop.
Week 17 The foetus is 5 to 6 inches long and weighs about 4 ounces.
Week 18 Body and facial features are well formed and evident as nose, lips and ears. Scalp hair is also seen.
Week 19 The foetus begins to respond to sound stimulus. You may feel the hiccoughs of the baby at times.
Week 20 Ears are fully functional and can hear the sound from the outside. The genitals can now be distinguished by a scan. The oil glands of the baby develop and secrete sebum.
Week 21 Baby starts moving around with the first movement being as thumbsucking. This can even be seen on an ultrasound. Baby movements in the form of kicks, flutters and punches may also be felt.
Week 22 Lower limbs are fully formed and toenails develop completely.
Week 23 The foetus begins to gain some weight and its skin is red and wrinkled.
Week 24 Fused eyelids separate to distinct upper and lower eyelids and allow the foetus to shut and open its eyes. The foetus is able to breathe and breathing movements are also present.
Week 25 Eyebrows and eyelashes are distinctly visible.
Week 26 The foetus can respond to external sounds and those within the uterus.
Week 27 An increase in the size of foetus gradually occurs.
Week 28 The foetus now weighs a kilogram and has a more proportionate body as the body grows to keep up with the size of the head.
Week 29 The foetus is 14 inches long.
Week 30 The foetus weighs 2.5 pounds and its lungs continue to develop.
Week 31 The foetus grows and matures and acquires more fat.
Week 32 It now weighs 3 to 4 pounds and is covered by a thicker layer of vernix.
Week 33 The baby is mostly asleep and its movements are more coordinated. It now acquires a heads down position preparing for delivery.
Week 34 Kicks and movements become stronger and the fingernails reach the end of fingertips.
Week 35 As the lungs continue to develop, the baby nestles its head between the pelvic bones of the mother.
Week 36-38 Muscle tone is developed and the foetus can lift its head. It has soft earlobes with limited cartilage. Grasping skills improve and lanugo disappears as the baby gains fat.
Week 39-40 Testicles descend into the scrotum and vulva develops. The chest becomes prominent and the foetus prepares itself for delivery.

References

  1. Better health channel. Department of Health and Human Services [internet]. State government of Victoria; Pregnancy - week by week
  2. South Dakota Department of Health. FETAL GROWTH AND DEVELOPMENT. [Internet]
  3. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Fetal development
  4. Office on Women's Health [Internet] U.S. Department of Health and Human Services; Stages of pregnancy.
  5. National Health Portal [Internet] India; Intrauterine growth restriction (IUGR)
  6. AR Albu, IA Horhoianu, MC Dumitrascu, V Horhoianu. Growth assessment in diagnosis of Fetal Growth Restriction. Review . J Med Life. 2014 Jun 15; 7(2): 150–154. PMID: 25408718
  7. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; An Alcohol-free pregnAncy is the best choice for your bAby.
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