Baby Development - The beginning of a New Life

The exciting time of your pregnancy begins when two small cells unite and lodge in your uterus.

The miracle that is happening under your heart is an elementary experience: Your child grows up to meet you as an independent little personality.

There is nothing more exhilarating than following its rapid development from the time of conception to birth: Even at the end of the first trimester of pregnancy, the embryo can be recognized as a completely small person, even if it is only about 7.5 centimeters long.

The pregnancy is medically divided into three phases. Each so-called trimester lasts around three months or around 13 weeks. During this time, not only does the child develop, but your body and soul also go through various changes.





First trimester

The first trimester, which spans the first to fourth months of pregnancy, is considered the stage of adjustment and confrontation.

First month

First to fourth week

Week 1:
Strictly speaking, in the first two weeks of pregnancy you are not pregnant at all, but still have a completely normal monthly cycle. Since hardly any woman knows exactly when she will ovulate, the first day of her last period is used as the starting date to calculate the expected due date. However, this calculation based on “Naegel’s rule” has a small catch: It assumes a stable 28-day cycle for women, deviations are not taken into account. For shortened cycles, you have to subtract the corresponding days or add them for longer cycles.





Small math equation

How to calculate the due date of your baby: Date of the first day of the last menstruation - 3 months + 7 days + 1 year. For example, if July 3, 2018 was the last day of the period, it would be July 3. - 3 months = April 3rd + 7 days = April 10th. Then April 10th, 2019 would be the due date. Determining the due date is important in order to be able to observe whether the child is developing in a timely manner and when the delivery period is exceeded.

Week 2:

In the second week after your menstruation, influenced by the estrogen hormone, your uterine lining builds up again into a kind of thick "carpet". The corpus luteum hormone progesterone ensures that the tissue is soft and permeable enough to accommodate a fertilized egg. At the same time, an egg cell in the follicle matures to ovulate.




Week 3:

As soon as a sperm cell penetrates the cracked egg cell, the egg is fertilized. The gender of your child has already been determined, because the father is solely responsible for this: he has sperm with X and Y chromosomes. If the egg is fertilized by a sperm with the Y chromosome, you will have a boy.

About 30 hours after fertilization, the egg cell begins to divide up to a certain stage and then slowly makes its way through the fallopian tube into the uterus. In very rare cases, the embryo may implant outside the uterus. In this case, one speaks of an abdominal cavity or ectopic pregnancy, which has to be terminated for medical reasons.




Week 4:

As soon as its arrival, the germ, which is now the size of an apple kernel, "nests" in the nourishing mucous membrane of the uterus. It already gets nutrients from your blood through the placenta.



The placenta


The placenta consists of embryonic tissue. Together with the umbilical cord, it is the vital connection between you and your child. The placenta supplies your baby with oxygen, water, nutrients and vitamins for 40 weeks and also "disposes" of its waste materials. In addition, it filters toxins from the mother's blood through the so-called placental barrier, passes your antibodies on to your child and produces important pregnancy hormones.



Second Month

Fifth to eighth week 

Week 5:

Your menstrual period is now overdue. On a regular cycle, a pregnancy test will now be positive about three days after the expected bleeding. Commercially available tests react to the hormone HCG (human chorionic gonadotropin) in the urine. This hormone is produced by the placenta and the fetus and can therefore only be detected when the pregnancy has already reached a certain stage. Use your morning urine for your pregnancy test. This contains higher HCG concentrations, so pregnancy can be proven better and earlier. Exception: women who work at night should only carry out the test after a period of rest.

The heart of the approximately 0.5 centimeter embryo is already beating. Its main organs and the arms and legs begin to develop.




Week 6:

Your uterus is growing and is now about the size of a tangerine. Perhaps now you sometimes have intense, pain-sensitive breasts and your nipples are also getting a little darker. It can also happen that you suddenly become very tired during the day and feel limp and weak.




Week 7:

Fingers and toes of the embryo develop, the heart has also developed and beats twice as fast as that of an adult. Your child can already be seen in the ultrasound.

Week 8:

Your baby now measures a good 14 millimeters, about the size of a grape. Everything is aimed towards growth: the organs become larger and develop further, the face is also shaped: eyes, lids and the tip of the nose emerge, the inner ear develops. Nerve cells develop in the brain. In addition, your baby will begin to move - but you will not notice it yet.




Third Month

Ninth to twelfth week

Week 9:

You slowly feel that your stomach is getting bigger, maybe you have already gained some weight? The main reason for the increase in your weight is the increasing amount of blood in the uterus and placenta, the amniotic fluid and the increase in glandular tissue in the breast. However, the baby still weighs less than five grams! Something else changes noticeably: Your feelings will probably ride a roller coaster every now and then, and you will now react more emotionally than you were used to before pregnancy.




Week 10:

All vital organs are now developed and functional. They grow and mature and start to develop features such as fingernails and hair. At the end of the tenth week of pregnancy, your child takes another decisive step: From a medical point of view, the embryo now becomes a fetus.




Week 11:

The fetus, which is a little over four centimeters in size, is already sipping amniotic fluid, which is mainly formed by the inner membranes and from parts of the maternal blood. In the course of pregnancy, the amniotic fluid is constantly reabsorbed and produced again and again. It consists of 99 percent water, the remaining percent is made up of protein, sugar, salts and other trace elements as well as coagulants. The child's hairs and flakes of skin float in the amniotic fluid. Normal amniotic fluid is colorless and clear, but it can sometimes look a little milky. The normal amount of amniotic fluid is around 35 ml in the 11th week, 350 to 500 ml in the 20th week and 1000 to 1500 ml in the 36th week. After that, it decreases by around 100 ml every week.



Stable phase

Pregnancy enters the stable phase and the risk of miscarriage is now lower. In most cases, morning sickness also disappears.



Week 12:

The fetus is now about five centimeters long and weighs about 30 grams at the end of the 12th week of pregnancy. Sex development is complete and your child is moving his arms and legs, turning his head and already clenching his tiny fists. However, it does not control these movements itself; they are reflexes that get their impulses directly from the spinal cord.




Fourth Month

13th to 16th Week

Week 13:

Your child now measures five to six centimeters from head to bottom, at the end of the 13th week of pregnancy it is already seven to around eight and a half centimeters. It can now make sounds as its vocal cords are fully developed.

Now the fine body hair fluff, the so-called lanugo hair, also grows. The “fur leftover” serves as protection.




Week 14:

The gender of your child can be determined on the ultrasound. It is already busy sucking its tiny thumb, can blink and furrow its forehead. Your little one is getting eyebrows, and the hair on the head is already beginning to show.




Week 15:

Your child now does gymnastics all the time, with the powerful movements he strengthens his body muscles. His little heart carries around 100 liters of blood a day. In the meantime, your baby can also open and close its mouth, the suck reflex develops and they show increased swallowing and sucking movements.




Week 16:

In the next three weeks, your child will almost double their weight from around 100 grams and grow several centimeters. It is already exercising its lungs by inhaling and exhaling amniotic fluid. It now likes to play with the umbilical cord - it grabs it and pulls on it.


Second Trimester

In the second part of pregnancy, which lasts from the fifth to the seventh month, you usually go through a period of wellbeing.




Fifth Month

17th to 20th Week

Week 17:

Your child's hearing is already so well developed that your baby can hear the first noises such as the rushing of your blood and heartbeat. In addition, the birthing custard (vernix) forms, a kind of natural care cream that covers and protects the small body.




Week 18:

Your baby's trunk/neck and limbs in particular are now experiencing a growth spurt. It is already practicing breathing by raising and lowering its chest. The body proportions also change, the legs become longer than the arms, and the head-to-body ratio becomes more balanced. In extensive gymnastics lessons, your child trains all of the senses: if, for example, their feet hit the wall of the uterus, they pull them back. You may now feel your baby's movements for the first time - a wonderful moment, and not just for the first child!

Week 19:

The retina in the eye reacts to light stimuli. The development of the skin is also complete, but it is still so thin that the blood vessels show. The characteristic small skin grooves that make up the individual finger and toe print have been created on the fingers and toes.




Week 20:

Halftime! By the end of the 20th week, you are already halfway through your pregnancy. Your child's weight is around 300 grams and they measure around 15 cm from crown to rump. It diligently drinks amniotic fluid and excretes it as urine.





Sixth Month

21st to 24th Week

Week 21:

Your baby swims in about one liter of amniotic fluid, it can now orientate itself well in its surroundings, because its sense of balance is almost completely developed. Your child's heart will get bigger and stronger. There is still a small opening between the right and left atrium, which only closes after the birth.




Week 22:

Now your child already looks like a newborn, but it is still very thin and needs to get a little fatter. Its somersaults can now also be felt through the abdominal wall. At last the dad can make contact with the baby.




Week 23:

Now your child can hear your voice through the abdominal wall. Talk to him regularly and often, then he will later remember the familiar voice and it will calm him down. Your child has developed sleep and wake phases and can even be woken up by external movements. Towards the end of the seventh month, your child will already open their eyes, and eyelashes are already growing on their lids. You can easily see the long, now firmer nails on its fingers.

Week 24:

At the end of the 24th week of pregnancy, your baby has an average weight of 530 grams and measures 28 centimeters from crown to rump. You can now feel the upper edge of your uterus yourself at navel level.


Seventh Month

25th to 28th Week

Week 25:

The amniotic sac is slowly getting tighter for your child, but they can cross their legs, move back and forth, turn, kick and change their position within the uterus. Your uterus is now the size of a balloon and presses against your stomach and diaphragm. As a result, you may be short of breath or have heartburn more often.

From now on, with appropriate medical care, your child would have a good chance of survival if it were born too early due to its lung development.




Week 26:

Your uterus is already practicing light labor (so-called practice labor), which you will notice when your stomach gets hard for up to a minute every now and then. The contractions are painless, irregular, and slowly subsides - in contrast to labor pains, which get stronger and stronger. As long as it is not heavy and regular labor, which may even be accompanied by bleeding, there is nothing to worry about.



Practice makes perfect

The practice contractions are called "Braxton-Hicks contractions", sometimes they are also called "wild contractions". Braxton-Hicks contractions do not change anything in the cervix and therefore have nothing to do with the birth.

Week 27:

Your baby is now putting on fat more and more, his skeleton is becoming more stable and harder, the little fingernails and toenails are becoming stronger. Due to the growing uterus and the additional weight, the center of gravity of your body shifts. You may temporarily feel insecure while walking - make sure you have comfortable footwear in which you have a good grip.




Week 28:

Your child has reached around a third of its birth weight. His brain is also growing steadily, with important windings and furrows forming in both halves.

You can often feel that your baby has hiccups by making tiny, rhythmic movements in your abdominal wall. As a result, it trains the immature muscles of its diaphragm, which is later needed to breathe.

Third Trimester

You have now reached the last trimester of pregnancy, which includes the eighth to tenth month, and are therefore in the so-called "stress stage".





Eighth Month

29th to 32nd Week

Week 29:

Your stomach is getting bigger and bigger now. If you have a negative Rh factor, be sure to do the second antibody screening test (see page 172).

Week 30:

Your child's lanugo hair recedes and their scalp hair grows. Your little one is now also training "breathing" through the nose. You can now clearly feel his sleep and wake phases.

Even if it takes another ten weeks, your child is gradually preparing its body for the birth. The circulatory system “learns” to supply its most important organs such as the brain, heart and kidneys with blood in a targeted manner. When they later pass through the narrow birth canal, they receive an optimal dose of oxygen.

Week 31:

Many babies are already lying upside down, but this is not the final position yet, because they can turn around again at any time. So you don't need to worry if your child is still lying up straight.

Week 32:

Your child already weighs around 1700 grams and is around 42 centimeters tall. It gains about 200 grams of body weight per week. That's why it doesn't move as much now, and you may feel it less than before. It is best to lie down on your left side so that your child's weight does not press on the large vena cava to the right of the spine. If the large blood vessel is compressed, it can cause symptoms such as dizziness or nausea.


Ninth Month

33rd to 36th Week

Week 33:

The first stool, the so-called child pound or meconium, slowly collects in baby's intestines. The viscous, sticky, dark green to almost black mass consists mainly of swallowed lanugo hairs, skin particles, superficial cells of the intestinal mucosa and bile pigment. Usually, your child will not have a bowel movement until one or two days after it is born.

Week 34:

The maternity leave period starts here for you. If you have statutory health insurance, you can now apply for maternity benefit with your health insurance company. To do this, you need a certificate from your gynecologist or midwife about the expected delivery date. This will only be issued from this point on.

Week 35:

Your child's pupil reflex is now also working, his fingernails have grown to the fingertips. Babies' skull bones are not yet firmly interlocked and are still “soft” so that they can more easily adapt to the birth canal during birth. In return, the skeletal bones are getting harder and stronger.

Week 36:

Your baby is now almost a thousand times the size it was on its first day: about 46 centimeters long and about 2,700 grams. In the coming weeks it will continue to gain weight and form fatty tissue, which will protect it when the temperature changes after the birth. Your uterus has now reached its highest level: It reaches up to the costal arch, which often makes breathing and movement difficult. As a rule, this is the time to go into contractions, which also ensure that you can breathe better again. The usual 30 to 40 second long contractions “push” (the so-called preceding part), ie the head or bottom, slowly moves down so far that it makes contact with the bony border of the pelvic entrance.


Tenth Month

37th to 40th Week

Week 37:

Your child's lungs are now fully mature and can do their important job after birth. This is ensured by the so-called “surfactant factor”, which is now produced in sufficient quantities, without this the alveoli would collapse immediately after birth.

Week 38:

At the beginning of this week you will be “on time”. If your baby is now born, it will no longer be premature. It has completed its development and is ready for life outside the womb. The diameter of the head is now about ten centimeters. The cervix of the uterus has to open just as wide at birth.

Week 39:

Your baby is now around 50 centimeters tall and weighs around 3,000 to 3,500 grams and can only move very little because it has become too tight and small for him. Most babies have crossed their arms over their chests and bent their legs in the past two weeks.



Apply for parental leave

Don't just think about the upcoming birth, but also about the time afterwards: Would you like to take parental leave after maternity leave? Then you have to register this in writing with your employer - no later than one week after the birth.



Week 40:

Even if the due date determines the end of the 40th week of pregnancy: Only 5 percent of all babies are born on the calculated date. Actually, the appointment is more of a period: three weeks before and two weeks after.

Towards the end of pregnancy, the functionality of the placenta declines: the tissue ages and is increasingly unable to perform its previous tasks. At the latest, then your baby will give the starting signal for the birth.

We at Töpfer wish you all the best!



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