What Happens during Pregnancy - 40 Week Pregnancy Journey Guide

What Happens during Pregnancy - 40 Week Pregnancy Journey Guide

Every mother wants to listen to the first sounds of her baby, the first movement, the first milestone of each and every development. From the baby’s first ultrasound to the baby’s first kick, what all changes a mother can expect in her baby can be calculated by the pregnancy week by week calculator.

The unborn baby remains in the mother’s womb for 38 weeks, but generally the gestational period, that is the term for which the mother carries the baby in her womb lasts for 40 weeks. This is because it is counted from the time the mother had her last menstrual period, and not from the actual date of conception which occurs after two weeks of the last menstrual period.

The whole gestation period is divided into three trimesters:

The first trimester

Starts from the time of conception to the 12th week of pregnancy.

The second trimester

Starts from the 13th week, till the 28th week of pregnancy.

The third trimester

Starts from the 29th week and goes on till the 40th week of pregnancy.


The process which involves the fertilisation of the sperm with the ovum, and then the implantation of the fertilised zygote in the endometrium of the uterus is known as the conception. It is at this point of time that the gender and the inherited characteristics of the baby are decided.

It is extremely important to track the growth of your baby every week, in order to see if the baby is growing up properly. And that is why pregnancy week by week calculators are used. New would-be mothers visit their obs and gyne specialist regularly to check on the growth rate of their unborn babies. The various changes are listed out below according to the week they take place in.

Pregnancy Week 1-2

At this time, you are not actually pregnant. The counting starts right from the time of your last menstrual period. Actually, it is a lot difficult to pinpoint the exact time when the fertilization occurred. So, the gestational period is counted right from the time the new egg is released.

Pregnancy week by week

Pregnancy Week 3

This is the time where you can firmly say that you are pregnant. The zygote starts dividing and forms clusters of cells, first called the morula, and then the blastocyst, which consists of two layers of cells, the outer trophoblast layer, and the inner embryoblast. The trophoblast layer forms the placenta, which serves as the lifeline of the baby, as it supplies oxygen and nutrients to the growing foetus. The inner mass of cells gradually develops into the embryo.

Pregnancy Week 4

This is the time when the implantation takes place. The ball of cells is now no bigger than a poppy seed. It finds its way down the fallopian tube and gets implanted in the endometrial lining. The amniotic sac also starts forming. And most importantly the embryo starts producing hCG (human chorionic gonadotropin), the hormone which is responsible for showing the positive pregnancy indication in an urine pregnancy test. Also, the embryo now differentiates into three layers, the endoderm, the mesoderm, and the ectoderm. By the end of the fourth week, the foundations of the baby’s organs are firmly in place.

Pregnancy Week 5

The little ball of cells now resembles a tiny tadpole-like shape, with a distinguishable head, and a tail. A primitive heart starts to form. The heart is formed first because the circulatory system is the most important of all. The neural tube is under construction, which later on forms the brain and spinal cord. There is also the formation of a rudimentary digestive system.

Pregnancy Week 6

The baby’s nose and mouth start forming.

Pregnancy Week 7

The umbilical cord is formed and the limbs start forming.

Pregnancy Week 8

Growth spurts are occurring throughout the body and the limbs are growing longer. Eyelids are formed. The heart is divided into left and right chambers. The baby grows, and along with it, the amniotic fluid increases too.

Pregnancy Week 9

The tiny muscles start to form and the foetus can be detected on ultrasound.

Pregnancy Week 10

The stomach and kidneys are operational. The heart is fully formed. The teeth start forming in the gums. The gonads start forming too.

Pregnancy Week 11

The bones begin to harden. And the skin gradually turns from see-through transparent to opaque.

Pregnancy Week 12

Basic brain structures are complete, and the brain takes up half of the weight of the body. The heartbeat becomes loud and clear.

Pregnancy Week 13

Fingernails and the downy hair on the body start forming. Her chest muscles and vocal cords are developing slowly.

Pregnancy Week 14

This is the start of the second trimester. The baby’s posture improves. The coating of downy hair, called lanugo covers the body. The brain develops the left and right cerebral hemispheres. Body reflexes are established.

Pregnancy Week 15

The baby’s vertebral column starts to ossify. The urinary system is formed.

Pregnancy Week 16

Muscles are stronger. Facial expressions are observed. The eyes are sensitive to light and can make small movements. Thumb sucking reflexes can be developed.

Pregnancy Week 17

The heartbeat becomes steady. The baby can hear the mother’s voice. Fat stores are starting to develop under the baby’s skin 

Pregnancy Week 18

The baby’s first poop, meconium, starts forming in his bowels. The baby’s nervous system is under major construction.

Pregnancy Week 19

You can feel the baby moving inside. The skin of the baby is covered with vernix caseosa, a coating which protects his/her skin from getting pruney. 

Pregnancy Week 20

External genital organs are visible. Most of the fat that is formed is brown fat, which keeps the baby warm.

Body changes during pregnancy week by week

Pregnancy Week 21

Taste buds develop. So, you should try eating more vegetables and fruits, so that the child is a less picky eater later on.

Pregnancy Week 22

The baby’s fingers learn to grab onto different body parts.

Pregnancy Week 23

The blood vessels develop underneath and so the baby’s skin takes on a reddish hue. Keratin is being added to the baby’s skin and hair. This helps in thickening the skin. Specialized lung cells, pneumocytes, start developing.

Pregnancy Week 24

The baby is putting on more and more weight. The auditory system of the baby is rapidly developing. The hair on the baby’s body is still white and has yet to get pigmented.

Pregnancy Week 25

The surfactant, a chemical which helps the lungs to expand, once the baby is out of the womb, is starting to form. The baby draws in amniotic fluid through the nostrils.

Pregnancy Week 26

The eyelids open up. The bay starts blinking. The baby is becoming coordinated.

Pregnancy Week 27

The baby is now more than a foot long. The baby ingests amniotic fluid in large quantities and excretes urine.

Pregnancy Week 28

This is the beginning of the third trimester.  The baby begins to experience REM sleep. The baby starts hiccupping.

Precautions during early pregnancy week by week

Pregnancy Week 29

The baby grows stronger. The kicks and jabs feel more strong and frequent now.

Pregnancy Week 30

The lanugo or the peach fuzz around the baby starts shedding off since the fat keeps the baby warm now. The brain develops more grooves and creases. The surface area increases. The red blood cells are produced in the bone marrow of the baby.

Pregnancy Week 31

All the five senses of the baby are now operational. The baby sleeps most of the time.

Pregnancy Week 32

The baby settles into the birthing position, head at the bottom, the legs, up.

Pregnancy Week 33

The baby gains weight at a steady rate. The sharp kicks and jabs are more painful now.

Pregnancy Week 34

The vernix, the coating on the skin of the baby starts thickening. The hands and legs of the baby may be visible through the belly.

Pregnancy Week 35 

The percentage of fat in the baby’s body is now 15%. The space inside your uterus is now getting more and more cramped.

Pregnancy Week 36

The foetus looks more like an infant. In the case of first birth, the baby drops at the pelvic level at this time. This is known as lightening or dropping.

Which part of the pregnancy is the hardest

Pregnancy Week 37

If the baby has already dropped, the punches and kicks become less frequent due to tight quarters.

Pregnancy Week 38

The baby’s irises are now pigmented, though they may change colour once they are exposed to light. The lungs are fully mature. The baby is ready to live his life outside the womb.

Pregnancy Week 39

The tear ducts start developing. More fat gets accumulated. Hair may grow on the head of the baby.

Pregnancy Week 40

The baby’s umbilical cord is around 20 inches long. All the baby’s body organs and reflexes are now fully functional. The baby produces stress hormones which help the baby in accommodating with her new surroundings after birth. Mostly the partition occurs at this time, though some pregnancies last 42 weeks too.

What Are the precautions to be taken during early pregnancy?

Maintaining a balanced diet is the most crucial measure to be taken care of during early pregnancy;

It must include a proper amount of vitamins such as vitamin A, all vitamins B, for example, riboflavin, folic acid, cyanocobalamin.

Mother should avoid all kinds of alcohol, tobacco, and drugs also.

Avoid direct as well as indirect exposure to harmful chemicals, pesticides, weedicides.

The proper amount of sleep periods (8to 9 hours a day)is also a necessary factor.

Travelling habits should be safe and hygienic, such as using a seat belt and keeping a first aid kit with you.

Avoid all medicine unless your doctor approves it.

Avoid heavy weight lifting and bending.

Breast changes during pregnancy

Changes in breasts are one of the earliest signs of pregnancy. The hormones in the mothers’ body help in breast development.  Estrogen stimulates growth and prolactin stimulates milk production.

After delivery, there is increased production of estrogen and progesterone, and the prolactin secretion is at its peak, which promotes lactation.

In the first trimester, the breasts grow in size and may feel swollen and tender. The nipples grow larger and become sensitive.

In the second trimester, the milk ducts develop. So the breasts feel more heavy or full. Cup size increases. During the first few weeks of the second trimester, the breasts start producing colostrum.

In the third trimester, the breasts become denser and heavier. Nipples are more pronounced and can also change shape. The nipples and areola tale on a darker hue. Since the skin stretches over the growing breasts, it may start drying and itching. A gentle moisturizer can help in this case. Stretch marks can also develop.

So these are all the pregnancy changes week by week and the breast changes that you can experience during your pregnancy. Also, each woman is different, so do not become afraid if your symptoms do not match with the mentioned ones. You are doing great, and everything will turn out all right in the end.

Keep faith in yourself, and have a good day 😇

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