Pregnancy & Baby’s Development
Congratulations! Welcome to the wonderful journey towards motherhood – Pregnancy – which lasts for 40 weeks (This may extend a week or two more in some cases, but there is nothing to worry about in that case).
A pregnant mother needs a lot of support and care throughout this journey. Knowing the right facts and information is necessary for the mother’s and the developing baby’s health. Your baby’s first few years, beginning from conception, are the most crucial years of developing a strong foundation of cognitive learning and physical health. Parents-to-be have a great responsibility in their hands, and by having the right knowledge and care ensures a healthy pregnancy and birth.
This page will provide insight on development of the baby and changes in the mother’s body week by week.
The Beginning of Pregnancy
The first trimester of pregnancy is the first three months or first 12 weeks of pregnancy. The first step of pregnancy is conception, when the female egg is fertilized by a male sperm to become an embryo, which implants itself in the uterus. Fertilization occurs during the fertile days of a menstrual cycle, which occur almost in middle of the cycle, several days near the day of ovulation. Read More about Conception and Fertility.
Usually, the beginning of pregnancy is taken from the first day of the last menstrual period (LMP) because it is easier to determine LMP than the day of conception (which occurs around the mid part of the first month of pregnancy). So in the first two weeks of pregnancy, the woman is not yet pregnant!
Changes in Mom-to-be
Besides the quick and useful info here, you might also like to read about do’s and dont’s, what to eat, how you and your baby are changing together in each month of pregnancy. Please Click here to read more about pregnancy from the blog.
A newly pregnant woman will notice a missed period, and before that, some common signs of pregnancy, like nausea, craving for a particular food, slight fluid discharge from vagina, tingling of breasts, darkening of nipples and areolae, slight enlargement of breasts, tiredness and fatige, and frequent urination. Some women may not notice any of these changes, and may come to know about their pregnancy by the 5th or 6th week after observing a missed period.
Changes in Breasts – The increase of hormones estrogen and progesterone and increased blood supply lead to breast enlargement due to enlarged breast glands for preparation to breastfeed the baby. New pregnant mothers should buy new and comfortable bra sizes for supporting the breasts.
Tiredness – The increase in hormone levels and preparation of the body for supporting the growing baby can lead to a more than usual fatigue and tiredness, which can last for the entire first trimester. This is in a way good because this prevents the mother from physical exhaustion and putting excess physical strain on the body. In the first trimester, the baby is very small and weakly linked to the uterus. Physical strain can put pressure on the weak placenta and can lead to detachment of placenta from the uterus. The pregnant mother should take rest and relax and avoid getting tired and ask for help with household chores.
Nausea – Nausea is the most uncomfortable factor a pregnant mom would face, and this may last up to four or five months. She would feel nauseated on smelling a particular food or perfume, active kitchen, or after having a meal. Many call this Morning Sickness, but this can go on for the whole day. In excess nausea, whatever she eats is vomited out, and can lead to dehydration and weight loss. For relief, small and frequent meals can be taken, and the OB/GYN can also prescribe medicine for relief from nausea.
Frequent Urination: This is markedly observed by the end of the first trimester and not in the very beginning. Enlarging uterus compresses the bladder, which lies next to it, and the capacity of the bladder to hold enough urine decreases, and the frequency of urination increases. There is also a rise in blood volume, which makes kidneys more active. Coffee and tea should be avoided as much as possible, which increase the amount of urination. Lots of water, fruit juice and soup etc should be taken. There is also a rise in number of bacteria in the urine during pregnancy which can cause infections in the urinary tract.
Constipation – Caused by vitamin and folic acid supplements, and higher progesterone levels. It is advised to increase fluid intake, prefer foods rich in dietary fiber such as fruits, vegetables and whole grain cereals. Some safe pregnancy exercises can also help. Severe cases should always be reported to a doctor.
Stomach Cramps: These may be related to the increasing size of the uterus and is commonly observed in pregnancy. Cramps with vaginal bleeding can be a sign of miscarriage and the doctor should be immediately consulted.
The second month of pregnancy is just like the first one, though, if not yet, you may develop cravings for certain foods. Some crave for chocolates, ice creams, cakes, or flavorful and tangy foods. Also, you may feel intolerant to certain food odors, which may make you nauseous. You may be surprised that the aroma you liked earlier now makes you feel uneasy.
There may also be digestion problems like bloating in the stomach, occasional headaches, irritability and dizziness because of the changes in hormones. If you feel anything like this, it’s best to relax, take it easy and have some rest, or divert your attention to something interesting that makes you forget the feeling of discomfort. For example, reading a book or talking to a friend.
Blood supply to the breasts increases, aerola become darker and breasts become heavier, and you may need to buy new brassieres for better support and comfort.
There may be increased vaginal discharge. Using some absorbent pads helps keep the area dry and clean.
You may feel nauseous like previous months in pregnancy, but there may be some relief from the morning sickness by now and you may feel an increase in appetite. You will also notice a healthy glow on your face.
By the end of the third month, you will have gained quite a lot of weight and would also begin to show a protruding belly. However, doctors should be consulted to determine your weight goals.
For overweight women, it is often not healthy to put on too much weight as it can lead to the risk of diabetes. Your baby needs just 300 calories per day at this stage to develop normally. Therefore, eating everything that comes before you may not be a very good idea.
The fourth month is when the excitement really begins. If your morning sickness didn’t go away by the third month, it will surely go away now. Now is also the time when the baby might start kicking inside you. However, if it does not, there is no reason to panic. Sometimes, the baby starts kicking by the starting of the fifth month.
Your breasts will continue to increase in size during this period and the veins may become more prominent. Some women also develop acne or reddish skin during this time. This is because of the increased hormone levels and does not really signal a deficiency, although many people believe so.
By the starting of the fourth month, your uterus grows very large and is forced into your abdomen. Due to this, your lung capacity is reduced and thus, you may feel fatigued or out of breath without doing too much physical activity. It is best to take as much rest as possible.
It is also advisable to include a lot of calcium and iron in your diet during the fourth month as the baby starts developing teeth root and other parts during this period.
If you did not feel the baby kicking during the fourth month, you definitely will now. This is also the time when you will feel the most energetic. Thus, this is a good time to indulge in light exercises to keep yourself fit and busy. However, always consult a doctor before taking up an exercise regimen.
Although nausea and headache are completely gone by this time, you may experience a lot of heartburn and pelvic pain. Pelvic pain is normal during this period, but if it becomes intolerable, you should immediately consult a doctor.
The thyroid glands become overtly active during this time, which may lead to more sweat than normal. Apart from that, you may also see some fluid discharge from your breasts during this time which is normal and there is no need to worry.
The sixth month is quite similar to the fifth month of pregnancy. You continue to gain weight but there are no major changes in your body. You may still experience heartburn and constipation and continue to sweat a lot because of an overtly active thyroid gland. Some women also report nose bleeding at this stage. Such a phenomenon is normal and nothing to worry about. It happens because of increased volume of blood in your body.
You may also begin to see stretch marks in your body. Taking essential vitamin supplements after consulting a doctor may help in minimizing them.
This is the beginning of the third trimester where your belly becomes large enough to cause you difficulty in sleeping. It is best to use some extra pillows or sleeping on the sides (mostly on your left) for a comfortable sleep. Avoid lying on your back as much as possible. The uterus increases in size and pushes itself in the pelvic region, thus causing frequent urination.
The increased body weight and the increased size of the uterus may result in extra stress on the back. Avoid wearing high heels during this time and practice pelvic rocking to ease stress on your back. Pelvic rocking is done by getting down on all fours on the floor. Your arms and legs should be exactly parallel to each other and your back should be straight. Do not curve your back downwards or upwards. Begin the exercise by keeping the back straight and pulling up your abdominal muscles towards your back. Next, just relax your abdomen and allow your pelvic region to push forward slowly. Hold this position for a few seconds and get back to your starting position. Please watch this video for the same.
You can do the pelvic rocking exercise fifteen to twenty times a day, preferably at sufficient intervals. If need be, this should be done with someone’s help or in supervision of a doctor.
It is during the eighth month that you may begin to feel Braxton Hicks contractions, also known as false labor. These contractions are characterized by tightening of the abdomen which comes and goes. These contractions are normal and nothing to be worried about. They happen as your uterus prepares itself for child birth.
Your pelvis keeps on increasing in size as the baby drops down in your pelvic region, called as engagement. During this time, you may experience increased pelvic pressure, which may further be accentuated by the increase in size of your baby. You may also experience discomfort in your rib cage region as the baby pushes itself into the region with its increasing size.
You are most prone to injuries during the ninth month of your pregnancy, so be careful. The hormones produced in your body to loosen your pelvic muscles may make you feel clumsy and restless. At this stage, you may find it really difficult to get a comfortable sleep because of physical and emotional stress.
The baby puts pressure on the pelvic walls while the thoughts of labor may keep you awake at night. Apart from that, your breasts also tend to swell during the ninth month, as the body prepares them (breasts get filled up with the baby’s first feed – colostrum) to feed the soon to arrive baby.
This is when you are past your due date and all you need to do is wait. Your hands, feet and other body parts may appear swollen (edema) at this point in time due to water retention. It is best to pay attention to uterine contractions during this time. When contractions occur for a prolonged period and close together, usually it indicates time for the baby’s arrival.
Going past the due date is not really worrisome. There are a lot of women who have delivered perfectly healthy babies past the due date. However, it is advisable to visit a doctor and undergo tests when you go past your due date. The tenth month of pregnancy isn’t much different than the ninth month, except the fact that you may feel more impatient and need to be more careful than usual.
Baby’s Development – Week by Week
In the beginning, the baby is just a single cell – the female egg, and after it gets fertilized by the sperm inside the fallopian tubes, it rapidly starts to multiply into many cells (blastocyst) and starts moving towards the uterus for implantation. Pregnancy begins when the egg is fertilized and we will call it as day 1 or first day of pregnancy. Though beginning of pregnancy is generally taken from the first day of last menstrual period, but to easily explain the development of the baby, we will follow this method.
Note: The details provided here are more general or approximate in approach. Every baby develops at a different pace, and a slight variation from the given developmental milestones of a baby is absolutely normal. Your OB/GYN is the best person to guide you about your baby’s development.
Weeks 1 and 2
Your body is preparing itself for pregnancy and is following a normal menstrual cycle. The day of ovulation is near (which occurs usually 14 days before the first day of the next period, when the egg or ovum is released by the ovaries towards the fallopian tubes). After the ovulation process, the released egg will wait inside the fallopian tubes for the sperms to reach it, and fertilize it. Sperms have a lifetime of 3 days within your body, so 3 days before and after the day of ovulation is the time to conceive.
Day 1 – The most active of the thousands of sperms, which are released inside the vagina during intercourse, reach the egg inside the fallopian tubes. The ovum already present there, gets fertilized by one of the hundreds of sperms that try to fertilize it! Congratulations, your pregnancy has begun! Though you are not aware of it at this moment…
Day 3 – The fertilized egg divides into 8 smaller cells and is known as a zygote. The eight cells adhere to each other for further development.
Day 4 – The eight cells form an outer layer of cells and an inner cell mass.
Day 5 – From the above stage, Blastocyst is formed, which consists of an outer layer of cells (trophoblast), blastocyst cavity, and the inner cell mass. The blastocyst is contained in the zona pellucida, the outermost layer (like an egg shell) of the female egg or ovum. Till now there has been no increase in size from that of the egg, and the cell division has lead to formation of smaller cells only.
Day 6 – the zona pellucida breaks and the blastocyst moves out of it – a stage known as zona hatching, in order to embed itself in the uterus.
Day 7 – The hatched cell mass starts invading the uterine wall to begin embedding itself.
Day 9 – The cell mass has completely embedded itself inside the uterine wall and inner call mass differentiates itself into epiblast and hypoblast, trophoblast being the outer cell layer as it was during the blastocyst phase. The embryonic phase has begun.
Day 12 – The epiblast and hypoblast of the inner cell mass form a bilaminar disc.
Second Month of pregnancy begins.
Days 13 – 16: Primitive streak is formed and 3 layers of cells (ectoderm, endoderm and mesoderm) are formed at the junction of the layers epiblast and hypoblast of the bilaminar disc. This is followed by formation of a yolk sac (from the endoderm) for providing nutrition to the growing embryo, and amniotic sac (from the ectoderm) for the baby’s protection is formed. Primitive blood vessels (non vascular at first) are formed, to make contact with the maternal blood.
Days 17 – 20: Between the yolk sac and the amniotic fluid, the baby is developing – the neural groove (spinal cord), primitive brain, primitive vertebrae, and the other end which will form the tail, appear. The baby is now 2.1mm in length. Formation of heart begins.
Days 21 – 24: The baby is now about 4mm in length and primitive heart appears outside the little body which soon begins beating! The baby has small arm and legs in the form of buds. Primitive eyes and ear pits are formed.
Days 25 – 28: Primitive forms of major organs – lungs, pancreas, liver, gallbladder, urinary system and spleen start to appear. The facial feature – mouth, starts to form.
The third month of pregnancy begins.
Days 29 – 32: The brain and eyes develop further; small pits at the place of nose form. Arms and leg buds elongate, with hands and feet appearing as little paddles.
Days 33 – 36: Blood flows through tiny vessels connecting the embryo, yolk sac and other membranes. Formation of kidneys begins. The baby measures about 8mm in length by now.
Days 37 – 40: The hands and feet on the arms and legs can be clearly identified with little fingers that are still webbed. Formation of external genital organs begins during this time. The baby is now around 13mm in length.
This is the last week of the first trimester.
Days 41 – 44: By this time, all major organs have started developing or are already developing. In the ultrasound, movement of limbs can be observed. The hair follicles start forming. This is the time when primitive forms of all major organs are present in the baby, and therefore the embryonic stage ends. The fetal stage has begun.
The fourth month of pregnancy begins with this week. Your baby is now in the beginning phase of the fetal stage as all the vital organs of the body are formed. Though all organs keep developing, the baby will grow more rapidly in size and shape by building bones, muscles and skin tissue. External genitalia form during this time and sex prediction can be performed using ultrasound.
The baby is now almost 4 inches (10cm in length). Muscles are forming and bones are getting stronger. Facial muscles are more developed and now the baby can smile, frown and can suck her thumb. Her body movements are now more active.
Very fine hair (called lanugo) start forming on the scalp and rest of the body. Eyebrows start forming but are not clearly visible. Her heartbeat can be heard using Doppler or ultrasound. Neck is now visible.
External genitalia are now developed. Her skin is still bit transparent and blood vessels below the skin are visible. Meconium (first bowel that is formed when the baby takes in the surrounding amniotic fluid, shed lanugo, bile and water) has begun to get collected in the intestines.
Weeks 17 to 20
- The baby is now about the size of your hand (open and spread out) or about 20 cm / 8 inches in length.
- The baby’s muscles and bones are more developed and the movements have become more rapid and active.
- You can now feel your baby’s movements for the first time, which is known as quickening – which feels like gurgles and bubbles in the stomach.
- Nails, eyebrows and eyelashes become visible and lanugo can be seen all over her body.
- Size of the uterus is now increasing to accommodate the growing baby and the uterus starts moving towards the upper side of the stomach (1cm up every week from the end of the 20th week).
- Fingerprints and footprints are more developed.
Weeks 21 to 24
- The baby now starts appearing more or less like a newborn, but still has red and wrinkled skin and little fat. She may weigh nearly 750g by this time and can be about 30 cm or 12 inches in length. The size of the uterus keeps increasing and you appear pregnant.
- The movements of the baby are now more active and can be felt at different times throughout the day.
- The baby develops a sleep pattern. She may be asleep for several hours and then be awake for the next few hours.
- Eyes are almost completely developed, and the eyelids are beginning to part.
Weeks 25 to 28
- Eyelids can now part completely, and the baby can now open and close her eyes.
- The nervous system and brain are rapidly developing like previous weeks of pregnancy, and by this time the brain has begun to control some body functions and baby also experiences REM sleep and also has dreams. Alcohol consumption during this time or during following weeks will have an adverse affect on the baby’s brain development.
- Ears are more developed and the baby can hear sounds better.
- Baby’s movements become more strongly felt.
- The baby keeps accumulating fat tissue.
In this final stage of fetus development, the baby prepares for birth and accumulates fat tissue under the skin. The skin also loses translucency and becomes more developed and opaque. Most of the internal and external organs are well developed at the beginning of this trimester, but the brain, lungs, skin and sensory organs are the ones that develop further to face the outer world during this time. The baby sleeps for 14 to 17 hours in a day. This is not continuous. There are periods of short naps – deep motionless sleep, REM sleep with movements and periods of wakefulness all during the day.
Weeks 29 to 32
- The baby is now about 40cm in length and weighs near 2kg.
- Near this time, fat tissue build up beneath the skin expedites.
- Skin pigmentation begins around this time.
- Sensory organs and related parts of the brain begin rapid development (ears, nose, skin and eyes) and the baby begins to sense the surrounding environment more clearly.
- Baby’s sense of smell also develops further and he / she can smell the surrounding fluid. Studies and observations have shown that the amniotic fluid is known to contain a faint aroma and taste of the food eaten by the mother. The smell of the amniotic fluid therefore helps in building the baby’s future food preferences.
- Alveoli form in the lungs and the baby begins primitive breathing movements.
- The baby prepares for birth by storing iron, calcium and phosphorus in the body.
- Now the baby can sense light and dark as his / her pupils can contract and expand with changes in surrounding brightness.
Weeks 33 to 36
Your baby is now almost like a newborn and has better chances of survival outside the womb.
- She is now near 45cm in length and weighs around 2.5kg or bit more.
- Her brain is rapidly developing and making nerve connections by sensing the surrounding smell, noises and light. The nervous system develops quite fast and very fundamental and important development occurs in the central nervous system around this time.
- Lanugo sheds from the skin. The baby swallows some of it and it forms part of the baby’s first bowel.
- She may have shifted downwards towards the pelvis.
- The space inside the womb is now decreasing and therefore the baby’s movements may change. The baby has less room to straighten legs and therefore kicking may change to rolling about.
- Sleep patterns may become more rhythmic. The baby now sleeps for longer and also wakes for longer periods.
Weeks 37 to 40
These are the final weeks of pregnancy and your baby is now much like a newborn.
- The baby will now have thick hair growth on scalp (but the thickness of hair growth may vary as genetic factors also contribute, some babies have good hair growth whereas some babies may have very less hair on their scalp).
- The baby has been building up immunity since the beginning of the third trimester.
- The baby is now about 48 cm in length and weighs about 3kg.
- Your baby would have shifted down towards the pelvis in a head down position. The baby’s lower body occupies the upper and larger part of the uterus and the head moves down towards the cervix. This is known as lightening. This way there is less pressure on the diaphragm and stomach which is comforting for pregnant mothers, but they may feel a little pressure in the pelvic region. This position indicates the baby’s readiness for birth.
- All of the baby’s organs have developed to an extent that he / she can face the outside world and has excellent chances of survival outside the womb.
-Pregnancy for Dummies by Joanne Stone, MD, Keith Eddleman, MD, and Mary Duenwald
-From First Kicks to First Steps by Alan Greene, M.D.