In this article, we are looking at the dates according to the last menstrual period (unless mentioned otherwise) to correspond with the dates given to you by your doctor.
Week 1 to 4
The most amazing miracle first occurs when the sperm cell meets the egg in the Fallopian tube, usually 12 to 24 hours after ovulation.
These cells then fertilize and make its way to the uterus, a place it will call home for the next 266 days. During this journey, the cells are continuously duplicating and by the 3rd day after ovulation, consist of 16 cells and referred to as a blastocyst. This blastocyst is smaller than the head of a pin and consists of an outer layer of cells (trophoblast) which ultimately forms part of the placenta while the inner cells (embryoplast) develop into the embryo.
6 days after ovulation (hence week 3), the blastocyst attaches to the lining of the uterus and this process is called implantation.
During week 3, the fetal membrane (amnion) and the amniotic cavity are formed. The amniotic fluid which is initially derived from the filtrate of mommy’s blood fills the cavity. The purpose of this fluid is to act as a shock absorber for the fetus, help regulate fetal body temperature and prevent adhesions between the skin of the fetus and surrounding tissues.
The cells beside the amniotic cavity are called the embryonic disc which forms the embryo. The cells have been dividing rapidly and at approx. the 12th day after ovulation, the yolk sac is formed which at this stage is the primary source of nourishment for the embryo.
Baby, at day 28, is approx. 0,2mm or as big as a grain of sand.
Mommy, however, may suspect that she is pregnant due to a missed menstrual cycle.
A pregnancy test done at this stage would have a positive result.
HOW EXCITING!!!!!!!!
Week 5
During this week, the cells of the embryonic disc differentiate into 3 distinct layers:
· the outer ectoderm,
· the middle mesoderm and
· the inner endoderm
These layers form so quickly that it is difficult to determine the exact sequence of events.
As the embryo develops, the outer ectoderm layer forms: the skin, nails, hair follicles and lens of the eyes. It also forms the lining for the ears, nose, sinus, mouth, anal canal enamel, chest glands and all the parts of the nervous system.
The mesoderm layer of the cells form the muscle cartilage, bone, lymphatic tissue, spleen, blood cells, heart, reproductive organs and the kidneys and ureters.
The endoderm, however form the lining of the gastrointestinal tract, urinary bladder, gallbladder and liver, the tonsils, trachea, lungs, thyroid and pancreas.
The development of the brain and the nervous system begins early in this week.
The primitive spinal column is approximately one third of the length of the embryo. Before the end of this week the heart begins to develop. The heart muscle cells start joining in an s-shape to form two tubes which then unite to form a common tube, the primitive heart tube.
BY DAY 36 THE HEART STARTS BEATING!
At the end of this week the primitive gut elongates and differentiates into an anterior foregut. At this stage the midgut still opens into the yolk sac.
The kidneys are being formed, and things are growing rapidly now.
Week 6
During this week of fetal development, the respiratory system begins as an outgrowth called the laryngotracheal bud. This bud elongates and differentiates into the larynx, glottis, and trachea with the distal portion forming the bronchi and lungs.
The umbilical cord is developed and serves as baby’s lifeline while in utero.
It is this umbilical cord that is responsible for transporting oxygen, removing waste and supplying the necessary nutrients for the remainder of the pregnancy.
The cells that develop into the eyes form thick circles on both sides of the anterior portion of the embryo soon to become the head. Nostrils are formed and soon the nerves running from the nose to the brain appear.
The brain is developing at a phenomenal rate with the neural plate consisting of a forebrain, midbrain and hindbrain.
Did you know that over the course of the remaining months that your baby's brain will develop over 100 billion neurons? This is just the beginning!
GET THIS EMBRYO’S UNIVERSITY APPLICATION FORMS READY!
The total length of the embryo is approximately 5mm.
Week 7
The yolk sac now constricts and detaches from the midgut which seals. The oral cavity and gastrointestinal are developing to form a continuous tube from the mouth to the anus.
The foregut develops into the pharynx, oesophagus and stomach while the midgut is transformed into the small intestine (the duodenum, the jejunum and the ileum), cecum, appendix and start of the large intestine known as the ascending colon. The hindgut forms the rest of the large intestine (the transverse and descending colon).
Towards the end of this week, the lymphatic system begins to develop from the mesoderm layer. The embryo which is curved into a C-shape is now covered in a very thin layer of skin. The extremities start making their appearance as small elevations at the side of the trunk, known as limb buds.
The structures of the ears as well as the maintenance of balance start to form.
Teeth even begin to develop under the gums - Thankfully, right now you won't be dealing with the dreaded teething pain!
Week 8
This clever little embryo’s brain has enlarged significantly with the head bigger than the rest of the body. Don’t worry, it is very normal; the body’s growth will catch up! The eyes, eyelids, nose and ears are rapidly developing while the muscles, spinal column and organs continue growing.
This week the upper limb buds start forming into arms, forearms and hands while in the lower limb buds the thighs, legs and feet become visible.
Development progresses and the salivary glands, liver, gallbladder and pancreas are formed. Baby is now equipped to deal with digestive enzymes and start processing the insulin and glucagons the body needs to function.
The heart is now divided into four chambers, the right atrium, left atrium, right ventricle and left ventricle.
The heartbeat varies from 120 to 160 beats per minute, although in these early stages up to 175 beats per minute is acceptable. That miraculous sound of the heart beating can be heard on ultrasound at this stage, and should be made into a ring tone!
Baby measures 1,6cm from crown to rump (i.e. head to bum) and weighs about 1 gram.
Week 9
Growth continues and towards the end of week 9, the baby has doubled up in weight, now weighing about 2 grams and measures approximately 2,3cm from crown to rump.
Mommy is still feeling very tired and often emotional while most likely still experiencing the dreaded nausea and/or vomiting known as ‘morning sickness’, although ‘all day sickness’ is often a better description! Hang in there moms, it is a very good sign that all is going according to plan and you will soon be feeling much better.
Week 10
This week the shoulders, elbows and wrist area become apparent and baby has the ability to kick and box or even practice some dance moves. They are very busy, so parents get your running shoes ready; this little sausage is going to keep you on your toes! It is however still too early to be feeling any movements.
The liver and spleen starts producing red blood cells.
The eyes start moving from the side of the head to the front while the palate of the mouth and tongue starts developing.
At the end of this week baby is no longer regarded as an embryo but in medical terms is referred to as a fetus, although I am sure some of you have chosen other names such as ‘pip’, ‘popsicle’, ‘peanut’ or even ‘bean’.
At this stage all the main organ systems have begun to develop, although function is still minimal.
Week 11
The eyelids fuse shut and the irises begin to develop. The placenta, which is attached to the uterine wall, begins to function. The placenta allows oxygen and nutrients to diffuse into the fetal blood from mommy’s blood. Likewise the carbon dioxide and other waste products diffuse from the fetal blood into mommy blood at the placenta. It is important to note that almost all drugs, including alcohol passes freely through the placenta. The placenta also serves as a protective barrier, preventing most micro-organisms crossing it. There are however a small number of these that cannot be stopped such as AIDS, German measles, chicken pox, measles and poliomyelitis. The placenta stores nutrients such as carbohydrates, proteins, calcium and iron which are released into the fetal circulation as required. Finally the placenta provides the high levels of hormones, estrogen and progesterone, which are considered necessary to maintain pregnancy and develop the mammary glands with in the breasts for lactation.
At the end of this week, baby will be just over 3 cm and weighing over 4 grams.
Week 12
So much has taken place inside mommy’s tummy, and this little miracle continues to grow day by day! Baby’s vocal cords start forming, the nails and hair start growing and the muscles within the intestines start contracting which later aids in the digestion of food. The eyes move closer together while the ears progress to their normal position on either side of the head.
One of the vital organs, the liver, begins to function, by cleaning the blood, storing essential nutrients and providing essential chemicals.
Mommies are often feeling better at this stage and some can’t wait to go shopping for that gorgeous pink outfit or adorable blue babygro covered in trains and cars. Depending on the fetal position, ultrasound can be used to determine whether baby has the XX (girl) or the XY (boy) chromosome already. The baby’s gender is however determined by the daddy immediately upon fertilization. In theory, if fertilization takes place after ovulation, it is most likely to be a boy as the boy sperm reach the ovum first as they are faster swimmers. If however fertilization took place prior to ovulation, it is more likely to be a girl. The reason for this is that the boys tend to be faster but die off sooner, so if ovulation took place the boys reach the egg sooner than the girls. The girl sperm are slower but more resilient and last longer. You go girl!
It is however better to wait a little bit longer and be 100% sure before removing any labels and throwing away the receipts. In the mean time daddies, it might be a good idea to start saving for those karate lessons if it’s a girl, to keep all the boys away!
90% of the time, the mommies ‘gut’ feeling or instinct regarding gender is correct, but may be influenced by others around her.
Baby is approximately 14 grams at this stage, although bearing in mind that baby may grow at a different rate and later influenced by genetic factors.
Week 13
Hooray! You have reached the second trimester of your pregnancy.
During an ultrasound examination, and with a watchful eye, one can often see the baby’s chest rapidly expanding and retracting as the diaphragm practices the inhaling and exhaling movements.
Baby continues to grow and often mommies start showing external signs of growth too, with her favorite pair of trousers struggling to close…
Baby’s neck is growing and no longer resting on his/her chest.
It is recommended that the nuchal translucency (i.e. back of the neck) is assessed to determine the risk associated in having a Down Syndrome baby.
Week 14
Baby’s skin is extremely thin and translucent. Fine hair known as lanugo covers the skin, protecting it while suspended in fluid. This does fall off before birth, so you won’t be delivering a hairy monkey!
The thyroid gland, found in the neck, begins producing essential hormones.
Boy’s prostate gland, situated at the base of the urinary bladder, starts developing; while girls’ ovaries descend into the pelvis.
Babies continue with their aerobic or kickboxing sessions and may even put their thumbs in the mouth.
Week 15
Mommy may start experiencing fluttering sensations within her tummy. This could be baby’s break-dance session, although often difficult to differentiate this movement and that of bowel. If you haven’t felt anything yet, please do not panic! If this is your first pregnancy, the abdominal and pelvic muscles are still very tight making it difficult to feel. The position of the placenta also plays another important role. With an anterior placenta, a lot of the movements are absorbed as the placenta acts as a shock absorber. It may be as late as 22 weeks before first time moms feel any movement.
At this stage the fingernails, toenails and even eyebrows are beginning to grow.
Your little bundle is approximately 10 cm long and weighing 70 grams.
Week 16
Babies have found new toys, the umbilical cord, their toes or even cuddle up into the placenta as if it’s their pillow. Baby may experience hiccups already, although mommy probably wouldn’t be able to feel it yet.
Growth continues while the bones ossify and get stronger.
Week 17
By 17 weeks, baby weighs approximately 130 grams. It becomes difficult to measure the length of him/her as not the entire baby fits into the ultrasound screen. Babies are often curled up with their legs up in front of the face, probably practicing their yoga moves. They are extremely flexible, as the ligaments have not yet developed.
Week 18
9 months is a very long time to be swimming around within mommy’s tummy. Often our skin looks all wrinkly after half an hour of splashing around in either the bath or swimming pool. A white substance therefore forms on baby’s skin, known as vernix to aid in the skin protection.
At this stage baby’s vocal cords have developed, but will not be able to make any sound as air is required. If baby could speak, I am sure he/she would tell you how comfortable and happy he/she is. Inside mommy’s tummy is the best place for baby right now, a safe place where baby can continue growing.
Week 19
The hair on baby’s scalp starts growing this week. The growth may be really slow with a lot of newborns not having a great deal of hair. This is definitely not the stage to be rushing out and buying grips, clips or bobbles in the case of girls or even hair gel for boys!
Did you know baby swallows the amniotic fluid he/she is swimming in? This fluid slides down into the stomach, gets absorbed by the kidneys before continuing its course to the urinary bladder where it is urinated out and swallowed again…sounds disgusting I know, but very clean.
Not recommended for adult consumption!
Week 20
Half way! Women are pregnant for approximately 40 weeks, although babies come when they are ready, unless parents or gynecologist have opted for a caesarian section.
Growth has been phenomenal with baby’s kicks feeling stronger as the muscle development continues. At this stage the different nerve cells associated with taste, smell, hearing, seeing and even touch are being developed.
It might be a good idea to start playing relaxing music to baby or get daddy or siblings talking to mommy’s tummy. Hearing familiar voices or sounds that baby became accustomed to while in-utero, is thought to have a calming effect after birth.
It is recommended that between the gestational ages of 18 – 22 weeks, a thorough ultrasound examination, referred to as an anomaly or detail scan, is performed. This ultrasound examination can take up to 45 minutes to complete as every aspect of baby’s body is examined.
Week 21
If baby is a girl, her uterus, ovaries and vagina have formed while the boys’ testes start descending into the scrotum.
Baby’s tongue is now fully formed and if timing is good, mommy and daddy would be able to see baby swallowing or even pulling out his/her tongue on ultrasound.
At this stage mommies are often aware of baby’s routine or sleep pattern. A lot of babies tend to be more active after breakfast, lunch time and again in the late afternoon when mommies are more relaxed. Studies have shown the more relaxed mommy is; the more relaxed baby is! So dads, it is in your best interest to keep mommy relaxed… back massages, feet massages, breakfast in bed etc. (The plot thickens!)
Week 22
Baby continues to grow week by week and at this stage is often weighing 450 grams, almost a block of butter. Total length is approximately 27 cm, not quite the length of a ruler yet.
Baby’s eyelids, eyebrows and fingernails are fully formed while the brain continues growing.
It is important to remember that baby seen on ultrasound is still very skeletal as the adipose layer has not quite developed up till now.
Week 23
The proportion of babies head to his/her body and legs appear to normalize and appear quite similar to that of a newborn, although still missing the body fat.
The pancreas, an organ responsible for the production of certain hormones, starts producing insulin, which is essential in the breakdown of sugars. Baby’s brain, heart, lungs, spine, muscles and bones are growing nicely.
Week 24
The taste buds situated on baby’s tongue begins to form. During this week small sweat glands start forming in the skin. Muscle coordination of the hands and feet has improved while baby endlessly boxes and kicks mommy inside. Mommies may feel baby kicking and eagerly call daddy to put his hand on her tummy, but to everyone’s disappointment baby stops moving! These clever little human beings sense the pressure on mommy’s tummy and puts their hands in front of their faces (the classic leave me alone sign) and stops doing what they were doing. Daddies need to be patient and continue talking to baby so that he/she recognized his voice. (Don’t forget mommies feet massage too!)
Eyelids have started opening, and bearing in mind that everything is still swollen, it can be difficult to see on ultrasound. Depending on the ethnic group of the parents, baby’s eyes are often either blue or gray-blue or brown when born, but may change colour within the first 6 months.
Week 25
Some studies have suggested that at 25 weeks, baby’s nostrils start to open and they have the ability of having a preferred smell, so mommies don’t make any drastic changes to your perfume. Baby’s movements have improved and appear to be more controlled at this stage.
Please remember to take a lot of pregnancy photos of mommies growing tummy for the album!
Week 26
At this stage baby often weighs just under a kilogram and continues growing at an extraordinary rate, often picking up an average of 200 grams per week for the remainder of the pregnancy.
Baby’s lungs are going through astonishing changes with the formation of branches and air sacs. The lungs also secrete a slimy substance known as surfactant which ultimately enables the lungs to expand during respiration.
During this week, the optic nerves are fully formed and start sending messages from baby’s eyes to the brain. Due to this astounding progress, babies are thought to be light sensitive and if a torch is shone onto mommy’s tummy, baby would turn his/her head away from the light.
You may try this experiment at home!
Week 27
Every day that baby stays within mommy’s tummy, improves his/her survival rate as the lungs, heart, brain, bones, muscles and organs continue growing; getting ready for the outside world.
Week 28
The additional fatty layer underneath the skin is clearly noticeable when viewing baby during a 4D ultrasound. It is however important to remember that baby’s nose and lips are quite swollen at this stage due to the amniotic fluid. The nose however also tends to be rather flat, to facilitate breathing during breast feeding, enabling baby to breath from the side while suckling.
Week 29
Eyebrows and eyelashes are fully formed at this stage while the lanugo starts shedding from baby’s face. Baby continues to grow and definitely making his/her presence known. Mommy’s tummy is probably feeling more and more like a punching bag as baby continues the aerobic or kickboxing sessions.
Week 30
During this week the bone marrow takes on the enormous task of producing red blood cells that are responsible for transporting oxygen and nutrients throughout the body while simultaneously removing all the waste products such as carbon monoxide and other gases.
The tear ducts in the corner of baby’s eyes are now capable of producing tears.
Lanugo continues to disappear while the growths of baby’s toenails are almost at the final stage.
The fatty layers continue to accumulate below the skin, giving baby the healthy appearance. Parents, start getting baby’s modeling contract ready!
Although a generalization, babies often weigh approximately 1,5 kilograms.
Week 31
The brain continues to grow and develop with the production of billions of nerve cells.
Babies are still pretty active at this stage, with visible signs of the commotion seen on the surface of mommy’s tummy. Some have referred to this spectacle as some alien invasion!
Week 32
Babies who are still in a breech presentation (i.e. head on top and bum at the bottom) generally start turning so that the head is down (i.e. cephalic presentation). It is very normal for babies to move into this position at any stage prior to this, and there is no indication that baby would arrive any earlier.
At this stage of development, baby’s 5 senses, see, taste, touch, smell and ability to hear, are working. Baby however still has quite a bit of growing to do with the lungs being the last organ to complete development. The toenails are totally formed and almost ready for that pedicure!
Interestingly studies have shown that while babies are sleeping, they may have rapid eye movement (REM) in a dream-like state. Not sure what they dream about though!
Week 33
All the bones are growing and hardening while the skull remains quite supple and not completely joined; allowing for slight overlapping during the birthing process.
The amniotic fluid that baby has been swimming around in, starts diminishing. Due to the reduced fluid and lack of space, the acrobatic movements that took place beforehand tend to subside a little. By this stage babies often have a set routine when they are more active or enjoying their siesta, with their wake time most likely at 10pm. Good luck!
Week 34
By now baby has perfected the skill of blinking. His/her fingernails have reached the finger tips and would have the ability of scratching his/her face…book that manicure!
Mommy’s antibodies cross the placental barrier and are transferred to baby, providing some protection to various diseases. Breast feeding after birth would nevertheless improve the ability to fight off diseases too! Baby needs all the protection he/she can get.
Baby’s average weight at this stage would be about 2, 3 kilograms, and growing!
Week 35
The adipose tissue (fatty layer) continues to plump up the skin, especially the arms and legs at this stage. This layer helps to regulate baby’s body temperature.
In boys, the testes have completed their descent into the scrotum while the girl’s labia are swollen due to mommy’s hormones.
The uterus (a.k.a. womb) has expanded to 1000 times its original size, that’s some stretching!
Week 36
I bet mommy is feeling pretty uncomfortable at this stage. Baby has most likely started the descent into the pelvis, making it easier for mommy to breath as there is less pressure on her diaphragm and lungs. The trips to the toilet tend to increase due to the added pressure on mommy’s bladder. Baby’s lungs at this stage have developed completely, although functioning happens once baby is born.
Week 37
Baby continues to practice the breathing motion, strengthening the diaphragm. This may result in hiccups in baby, and is very normal. Their weight at this stage is approximately 2,9 kilograms, although genetic factors play a role. Hang in there, baby is nearly here. I hope your bags are packed and either in the boot of the car or strategically placed at the front door!
Week 38
Baby’s lungs are maturing and still producing surfactant, ready to cope with the real world.At this stage baby’s grip is becoming quite firm, ready to squeeze daddy’s little finger. I hope you have remembered to take a lot of belly photos to add to the photo album. Should baby decide it is time to escape the comforts of the uterus for the big world out there, baby would be classed as being born at full term. Normally caesarian sections would be performed towards the end of this week.
Week 39
I am sure mommy and daddy, even Granny and Grandpa are getting impatient. Babies come when they are ready. Make sure all the baby clothes have been washed and you have enough nappies ready! The lanugo has mostly disappeared except for a little on baby’s shoulders, arms and legs. This fine hair floats around in the amniotic fluid and is swallowed by baby. Baby’s intestines are accumulating all this hair and other waste products and referred to as meconium, resulting in baby’s first tar like poo. Its amazing how vomit, wee and poo becomes a natural topic once baby arrives.
Week 40
While baby remains inside, he/she continues to grow. The average birth weight is approximately 3,5 kilograms with a length of 51 cm. A number of babies are just too comfortable inside and not ready to face this world, some gynaecologist would allow you to carry for a further 2 weeks before making plans to induce labour. Remember to charge the batteries of the camera and cellular phones. Ensure the memory stick has been emptied giving you lots of space for those amazing first moments!
Cherish every minute, they grow up too quickly…Congratulations with the birth of your baby/babies!
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