Pregnancy : 1st Trimester

Pregnancy : 1st Trimester

First Trimester 1-12 weeks

  • Pregnancy Test – how to tell
  • Calculating Babies Due Date application as on
  • Physical Changes – what is happening to you and your baby
  • Baby’s development
  • Breast, nipple, body, tiredness & exhaustion, morning sickness and nausea, frequent weeing, excessive saliva and taste changes, fainting, dizziness, headaches, constipation, wind, libido, and sex drive
  • Emotional Changes
  • What to expect at your first pregnancy Medical visit?

Pregnancy Test – How To Tell

There is an array of pregnancy tests available on the market, however all test for the presence of human Chorionic Gonadotropic (hCG) hormone in either your blood or urine.

False positive/ false negative pregnancy tests

hCG is a hormone made by the placenta and is only present in your body when you are truly pregnant, hence generally a test that is positive is often truly positive! However false positives can occur in some circumstances such as:

  • You have an hCG-producing growth such as an ovarian tumour
  • Protein in your urine can give a false-positive result
  • Some medications particularly fertility drugs may cause a false positive result
  • If you have experienced a recent birth or miscarriage hCG may still be present in your body
  • The urine collecting cup is dirty - detergent residue can cause false-positive results
  • The test kit is faulty

Alternatively, false negative pregnancy tests are possible and usually happen when the test is done prematurely. The levels of hCG required to give a positive pregnancy result are high and so it is possible to get a negative result while your hCG levels are increasing to positive pregnancy levels.

Urine pregnancy tests

While urine pregnancy tests can accurately detect the presence of hCG, they are qualitative - merely giving a negative or positive result. Most urine tests need a higher level of hCG than a blood test to show a positive result and so may be slower to show a positive result.

The best ways to ensure that you get the correct result from a urine pregnancy test are:

  • Read the instructions BEFORE you take the test - not all tests are the same!
  • Test your first-morning urine - this will ensure that your hCG levels are as high as they can be. If you cannot use this urine, test urine that has been in your bladder for a couple of hours.
  • Do not drink a lot before the test - this will only dilute your urine and make the level of hCG lower than it would normally be.
  • Check with your doctor that any medications you may be taking (particularly fertility drugs) will not affect the result of your test

Some urine pregnancy tests can frustratingly not give you an answer either way - this is because your hCG levels are too high for a negative but too low for a positive result. Though, once your hCG level rises to the extent that it is no longer considered a negative result, it will continue to rise until you get a positive result.

One of the main drawbacks to using urine pregnancy tests early on (some tests can test for the presence of hCG as early as a week after your period was due) is that 30-50% of all embryos that attach to the uterine wall, detach again. This is different from the early miscarriage. With pregnancy tests able to give an early positive result, it can be very disappointing to discover that your positive has turned into a negative result.

Blood pregnancy tests

You can have a blood pregnancy test done by your doctor as early as 11-14 days after ovulation. After being sent to a lab for testing, the results of a blood pregnancy test can tell you two things:

Qualitative - whether you are pregnant or not.

Quantitative - how much hCG is in your blood. This is useful to estimate how far your pregnancy has progressed.

Blood pregnancy tests are 99% accurate and can detect a much lower amount of hCG than urine pregnancy tests and it is for this reason that many women still choose to have a blood test done after doing a urine pregnancy test themselves at home.

First Trimester

The first trimester is a period of major development for your fetus and of profound physical and emotional changes for you.

You may realise that you are pregnant straight away, however, many women will not realise they are pregnant until at least week four or five. This is one of the reasons why women are encouraged to plan for pregnancy.

During the first trimester of your pregnancy, your body is undergoing dramatic changes. By week six you may already notice your clothes getting a little tighter around your waist.

Physically you may experience some of the following symptoms during the first trimester:


As your body begins working overtime developing the foetus, you will most likely be exhausted during the first trimester. You should take plenty of time out to rest during this period. If you feel like having a sleep during the day, try to do so. If you are in a relationship, make sure your partner helps around the house or if necessary, employ a cleaner or ignore some housework for a while.


While we have all heard about morning sickness it is often not until you are pregnant that you realise you can be nauseous at any time of the day during pregnancy.

If you experience only slight nausea, you may find that snacking regularly on biscuits and cheese may help to alleviate the symptoms. If you have severe nausea and vomiting, however, consult your doctor as you may be nutritionally at risk.


This discomfort is one of the most common complaints of pregnancy. Heartburn is defined as a burning sensation in the middle of your chest; it often occurs after eating. You may also experience acid or bitter taste in your mouth and increased pain when you bend over or lie down. During the first trimester, nearly 25% of all pregnant women have heartburn. Later, it may become more severe when your growing baby compresses your digestive tract. Eat small, frequent meals. One sure way to get heartburn is to eat a large meal, then lie down!


This is also common in early pregnancy, brought on by two changes in your body. Increased hormones, whereby your body produces progesterone, which relaxes the smooth muscles of the intestinal wall and stomach, resulting in a slow down of digestion, and your blood volume increases. If you don't drink enough fluids to keep up with the increase in blood volume, you will experience dehydration which causes constipation. So, drink lots of fluids, exercise, and snack on prunes!

Do not use laxatives without your doctor's approval. If constipation is a continuing problem, discuss treatment at a prenatal visit. Try not to strain when you have a bowel movement as straining can lead to hemorrhoids.

Micturition (Urinary frequency)

You may begin to experience the frequency of urination early in your pregnancy (as early as one week after conception). With an increase in progesterone levels and secretion of hCG, the blood supply to the pelvic area increases, resulting in bladder irritation. As the uterus grows, it exerts increasing pressure on the bladder, resulting in the need to pass urine more often.

Breast changes

Breast changes can begin quite early in pregnancy with increasing levels of estrogen and progesterone. You may notice nipples become darker, and the breasts feel larger, heavier, and quite sore to touch. Wearing a comfortable bra can help alleviate some of the discomforts.

Research your options

Start researching the childbirth options that are available to you during this trimester. You will need to talk to your doctor and other mothers about the type of birth you want. You may also want to do some reading to bring yourself up to speed with the options available to you. A visit to the Essential Baby birth choices page will provide you with information about all your options.

Antenatal care

Throughout your pregnancy, you will have regular check-ups, or "antenatal visits" with your doctor or specialist. These visits will generally take place every month until 28 weeks, then fortnightly to 36 weeks, and then weekly for the last month. If you have any complications, the regularity of visits will be increased. You should take advantage of your visits by asking as many questions as possible. If necessary, take the questions written on a sheet of paper to ensure that you get the answers you need.

When you are pregnant, there are some basic precautions that you should take to ensure both your baby's and your health. Familiarise yourself with these precautions and speak with your doctor if you have any additional questions or concerns about how to rectify any problems that you see in your immediate work, home, or social environment.

They may include:


If you are a smoker or live with a smoker it is time to quit. If you need help call the Quit helpline (13 QUIT).


It is recommended that you avoid alcohol during the first trimester of your pregnancy. Obviously, by avoiding alcohol throughout your pregnancy, your baby will not be at risk as a result of alcohol. Often, women are advised that the occasional glass of wine is safe but the best option for your own peace of mind is to talk to your specialist to find out what is recommended for you.

Recreational drugs

Stop all recreational drugs immediately. If you find it difficult to stop, talk to your doctor, who can help you quit.

Prescribed medications

Check with your doctor as soon as you fall pregnant to find out whether prescribed medications are safe.

Rubella virus (German measles)

In Australia, most girls are vaccinated against the rubella virus as teenagers. However, the antibodies can lose their efficiency over time, so it is good to check your immunity prior to falling pregnant.

If you have been in contact with anyone who has, or who is suspected of having German Measles, you should contact your doctor for testing straight away. Rubella can cause serious defects in your baby including deafness, blindness, and heart disease particularly if it is caught in the first three months of pregnancy.


The biggest rule throughout your pregnancy is to ensure that you maintain a healthy, balanced diet. You should always keep in mind that your baby is getting all his/her nutrients from you!

If you are unsure about your diet or want some help, ask your doctor to refer you to a dietician. Get into the habit of checking packaging and labels and become aware of what you are eating.

Familiarise yourself with the following:

Quick food safety checklist

  • Ensure all meats, poultry, and fish are thoroughly cooked.
  • Ensure meat is thoroughly defrosted prior to cooking.
  • Do not allow raw meat or eggs to come into contact with other foods.
  • Eat only pasteurised dairy products.
  • Avoid soft cheese (such as brie and camembert) and processed deli-meats.
  • If you are a heavy coffee drinker reduce your caffeine intake.


Caffeine affects iron absorption and so it is recommended that pregnant women limit caffeine intake. The recommendation for pregnant women is to avoid caffeine if possible, but if you cannot get by without that morning cup of coffee, then limit intake to one cup per day. Caffeine is found in coffee, chocolate, and tea. Herbal teas make an ideal substitute for tea and coffee.


The tannin found in tea interferes with iron absorption and so should also be limited. (Most herbal teas do not contain tannin but check the packaging to be sure).


Listeriosis is a bacterial disease commonly associated with the ingestion of contaminated milk, soft cheeses, contaminated vegetables, and ready-to-eat meats such as deli-meats and pate. Pregnant women may have no apparent infection but there can be a risk of fetal infection.

Symptoms of Listeriosis include fever, aches and pains, intense headache, nausea, and vomiting. During pregnancy you should take particular care to ensure all meats are thoroughly cooked, vegetables thoroughly washed, and that you eat only pasteurised dairy products. An unborn child affected by Listeriosis may be stillborn and the bacteria can cause recurrent miscarriage. Check with your doctor or dietitian if you want more information.


Toxoplasmosis is a parasite that can cause serious effects to your unborn child including brain damage and blindness. The infection can be found in raw meats, cat and dog feaces, and contaminated soil. If you have pets or have any concerns at all about Toxoplasmosis, discuss them with your doctor.

Some guidelines for avoiding Toxoplasmosis include:

  • Do not eat raw or undercooked meat.
  • Do not handle cat litter or do any gardening in the soil where cats have defecated.
  • Wear gloves when gardening.
  • Be strict about washing hands after petting animals.


Botulism is a rare but severe form of blood poisoning caused by improperly canned or preserved food such as cured ham or pork. Botulism causes progressive degeneration of the nervous system and muscular paralysis.


Salmonella infection is most often traced to eggs and chicken meat. It is advisable to avoid foods that contain raw egg and always cook chicken and eggs well. Wherever possible, purchase free-range eggs and chicken. Symptoms of headache, nausea, abdominal pain, diarrhea, fever, and shivering develop approximately 12 - 24 hours after infection and last for 2-3 days.

Work-related hazards

If you plan to work throughout your pregnancy then it is essential that you take the time to assess your workplace and the activities that you are involved in daily to determine if there are any potential hazards.

If you have concerns about your job or your environment, discuss them with your doctor. If your work environment is not suitable, or if your work activities pose a risk, then your employer should transfer you to an alternative job while you are pregnant.

Do not become overheated for long periods

Overheating your body can be dangerous to your baby, in the first trimester. In particular, hot spa baths and saunas can cause fetal abnormalities.


Generally, traveling does not cause concern throughout most of your pregnancy. The main things to keep in mind are;

  • Pregnancy can increase your sensitivity to motion sickness
  • If travelling by plane, you should not travel after your seventh month
  • If travelling long distances in a car or train take along something to drink and try to take breaks and move around regularly - try not to get cramped into one position for a long time
  • If you are travelling internationally, speak with your doctor about required immunisations and what impact they can have on your unborn baby
  • Also, read food hazards to ensure you are familiar with potentially dangerous foods and drink bottled water.


Any vaccinations that use live viruses are avoided during pregnancy, including Rubella, measles, mumps and yellow fever. It is vital that you make your doctor aware that you are pregnant prior to having any immunisations. Immunisations are required for travel to some countries, and these should be discussed fully with your doctor prior to finalising any travel plans.


The average length of pregnancy is around forty weeks, though to deliver two weeks either side of this is still considered normal. Babies take on average, 38 weeks to grow to maturity but because we cannot pinpoint exactly when conception occurs, we count 40 weeks on from the date of the woman’s last period. Two weeks after this start is when most women are at their most fertile and more likely to have conceived.

First Trimester

For at least half of the first trimester, most women do not even realise they are pregnant. Even though it doesn’t seem to make sense that we count pregnancy weeks from before conception even happens, it is the only way to estimate when the due date will be. Using a due date calculator (see attached) and counting 40 weeks from the first day of the last period, it is possible to work out with a fair degree of accuracy when the baby is likely to be born. There are no guarantees of course, because often babies make up their own minds about when they want to come into the world.

The first trimester is a time of tremendous development. There is only a window of time, at around 12-24 hours after ovulation when an egg can be fertilised by a single sperm. This normally occurs in the fallopian tube, whilst the lining of the uterus has built up to provide the ideal environment for the fertilised egg to implant. If fertilisation does not happen, the endometrial lining of the uterus is shed at the time of the woman’s next period.

From the moment when a sperm and ovum connect, the tiny group of cells sets about developing its own separate and unique identity. The placenta is formed and plays a vital role in supporting the pregnancy week by week and releasing hormones which regulate the baby’s growth.

In this series, we will look at each of the 13 weeks in this important trimester and see that however tiny it is, vital foundations are being laid down to optimise your embryos chances of survival. We will discuss the changes your body is experiencing and how you may feel. We will also look carefully at how your baby is developing.

Week 6

This week marks the start of your embryonic period (weeks 6-10) and sets the basic foundations for your baby's life. The embryo is sensitive to any negative factors (alcohol, nicotine, excess caffeine, chemicals and pollutants) that may hinder its development, so it is advised to avoid and discontinue use.

This week the embryo develops 2 cavities, the amniotic sac and the yolk sac. The amniotic sac continues to enlarge and gradually envelops the embryo and body stalk. The yolk sac never attains a large size and disappears as soon as the fetus begins to obtain nourishment from the placenta. The body stalk that connects the embryo to the developing placenta (trophoblast) gradually becomes elongated and develops into the umbilical cord, containing 2 arteries and a single vein.

You may start to develop other more noticeable signs of pregnancy, such as nausea possibly accompanied by vomiting (especially in the morning), breast soreness or tenderness, the need to urinate more frequently, fatigue, and constipation. Do not use laxatives without first talking to your doctor. Try to exercise, drink more fluids and eat foods that are high in fibre.

Your baby

By this week, your baby's heart is prominent and beating. The next step is the development of your baby's own unique blood vessels, and a blood supply that is separate to yours. Your baby's circulation first uses the resources of the yolk sac, then later the placenta. Its circulation is closed (covered by the trophoblastic covering) and does not mix directly with your blood. It is your blood that is open to the uterus and feeds the baby, so if placental separation occurs, your blood will be lost, and not the baby's.

By the middle of the week the neural tube closes at your baby's head, where it will form the early brain chambers. By the end of the week the tube has also closed at the bottom of your baby's back. The arm and leg buds are forming, and various organs and other body systems are under way. With all these physical changes, the embryo develops from a layered disc to adopt a C-shaped curvature, taking on a curved body form with a head and tail.

Baby has been busy already! Embryos grow and develop at varying rates but by week six of your pregnancy baby resembles a tadpole and is roughly half a centimetre (the size of a lentil). Previously following conception your little tadpole has been curled up, however this week it starts to unfurl, and limbs start to lengthen into arms and then legs with feet and hands resembling tiny paddles. Baby’s head is oversized with dark spots where eyes and nostrils will develop, and small divuts for ears.

Baby’s heartbeat can now be seen in an ultrasound and beats almost twice as fast as mums at about 120 times per minute! Blood begins to course through the teeny body and organs are just starting to develop including a digestive system, kidneys, bowel and two little buds which will form into lungs.

Week 7 : You

While you may not be able to show the world, you are pregnant yet with a baby belly, internally there are changes happening. Your hormones have increased to sustain your pregnancy and there are physical changes which may reassure you that, yes, you really are pregnant. It is more than likely you are going to have cravings. Often the stress of trying to resist can cause more harm than having that second Tim Tam with a hot chocolate chaser and pink marshmallow on the side. Make your motto: 'everything in moderation' and you will stay healthy and happy all through your pregnancy.

It's important to take pre-natal vitamins as recommended but watch out for constipation. Sometimes the extra iron can cause you to become less regular. Try switching to another brand, however if the problem continues to persist ask for professional advice. Feelings of heartburn or indigestion can be relieved by eating smaller meals more regularly. If you find yourself snacking more than usual, try to stick to healthy options such as peanut butter and celery sticks, or apple and cheese.

Your baby

The past week has been phenomenal in your little one’s growth, and your baby has doubled in size to around 1cm in length! The pancreas and appendix have grown. Bulgy little eyes have developed in astounding detail with a retina, optic cup and lens, and the tongue and inner ears are starting to form. Baby has the beginnings of reproductive organs; however, you will have to wait another 9 weeks until around week 16 to determine the sex of your baby via an ultrasound. Your baby is technically still an embryo, and by the end of week 7 a fine, transparent layer of skin is covering baby’s body and is developing in two layers along with the formation of sweat glands.

Your baby's progress - Week 8

Your little one has grown to around 1.5cm to 2.5cm this week and is now the size of a kidney bean! Almost half baby’s height and weight are made up of its head which has a little tongue, nostrils and the beginnings of a nose. Baby’s ‘tail’ (spinal cord) is receding and joints have developed giving a more human appearance – webbed fingers and toes are still present, but by week 8 your little one no longer looks like a sea monkey!

Although you cannot feel it yet, baby is beginning to move around! Bones are starting to ossify, and baby’s skeleton has begun to form. Most internal organs are present in their basic forms including the brain, heart, liver and lungs, and a network of blood vessels are pumping blood through the tiny body. Arms and hands are growing more rapidly than legs and feet, a process which continues throughout development with hand gestures such as grasping developing quicker than leg movement like walking, which does not develop until your little one is around one year old.

Your baby's progress - Week 9

Your little one is the size of a walnut! Tiny eyes are now covered by eyelids; however, they will remain closed for most of your pregnancy. There is not much to see in the womb anyway! With development of the neck region your baby can lift and turn its now rounded head, and week 9 brings with its tiny earlobes, and fingers and toes are nearing completion. Baby is becoming still more proportionate in relation to its oversized head, with the stomach growing and intestines moving from the umbilical cord into the abdominal cavity. Little nasal passages open this week, and baby’s diaphragm is also developing, which is vital for baby’s first breath when the day arrives in around 21 weeks!

Your baby's progress - Week 10

Congratulations, this week of your pregnancy is an exciting week! Baby goes from being an embryo to a fetus with all organs present and most major structures now formed. The brain is developing at a rapid rate and your baby’s nervous system is responsive! Baby weighs approximately 5 grams, and as baby becomes fully formed, its weight gain will rapidly increase, and its structures will continue to grow and develop to maturity. The kidneys are now moving into the upper abdomen area and the beating heart of your baby is almost fully developed. Baby now has taste buds and is capable of moving food all the way through to its bowls with a fully functioning digestive tract! Tooth buds are growing which will form the little teeth that will burst through your little one’s gums at the age of six months or so.

Your baby's progress - Week 11

Rapid growth is continuing this week, your baby has doubled in size and is between 5 and 7cm long and 8 grams! No wonder you are feeling tired! You can relax knowing that by week 11 baby is stronger and at a reduced risk of developing any congenital abnormalities.

Baby’s body has straightened out, and bones and ribs have appeared. A beautiful face is now formed, and baby can suck, swallow and yawn as it moves around your uterus and responds to touch, however baby is still too small for you to feel it yet. Baby has begun to develop a sense of smell which when combined with maturing taste buds creates their first experiences of taste and smell in the womb.

Your baby's progress - Week 12

Baby’s hands begin to wonder, and studies have shown babies like to touch and explore their own faces. Some babies make a sucking action with their mouths and others suck their thumb in the womb. Your baby now has a gag reflex, too. Lungs are being prepared for future air respiration and you your baby is practicing ‘breathing’ by inhaling and exhaling amniotic fluid.

At week 12 the placenta is still larger than your baby, and supplies your little one with oxygen, fats, proteins, vitamins and minerals. The placenta also conducts the ‘diffusion’ process whereby it filters out carbon dioxide and waste materials. Poo is building up in baby’s intestine to be released upon birth in a dark substance referred to as ‘meconium’.

Your baby's progress - Week 13

Congratulations you have now entered your second trimester! The first three months from conception were a period of rapid development, and the following three will represent a stage of rapid growth for your baby.

Baby’s head is still whopping and large in comparison to her growing body, but her nose and chin are now well-defined and bones like the ribs are forming. From this point on, baby’s body starts growing to catch up with that big head, and baby is likely to be around 7cm to 9cm and will enjoy sloshing around in 100mls or so of amniotic fluid.

Your baby can move in a jerky fashion, flexing the arms and kicking the legs. In fact, if you prod your abdomen, your baby will squirm in response, although you will not be able to feel it just yet.

Her skin is paper-thin and rather see-through, and if you could see her inside you, you could even get a glimpse through her skin of her functioning and still-developing organs.

Baby’s sense of taste and smell are more developed, and her amniotic sac will continue to increase in size and mass and fill with more fluid. Baby had better enjoy all that space she is got right now for somersaults and movement because in another few months it will get squishy!

Your baby's progress - Week 14

Your little womb tenant is now around the size of a lemon and could well be making his own sour facial expressions - baby is now capable of squinting, frowning and making other facial expressions. He is also starting to develop the ability to move their eyes this week, although his eyelids will remain fused shut for another three months. Thanks to brain impulses, his facial muscles are getting a workout as his tiny features form one expression after another. He is his own unique little person, and now comes complete with fingerprints and toe prints on the end of his digits.

Baby’s skeleton is becoming harder and more defined as the bones continue to ossify, and his arms have grown enough to be in proportion with the rest of his body. His legs have a bit more growing to do, but he is having a happy little time inside your belly. Between weeks 13 and weeks 17, your baby is practicing his full range of movements, which may occur in bursts that last for around 1-2 minutes but have been studied as lasting up to 7 minutes.

Baby may be developing his own favourite resting place in the amniotic sac, where he will retreat after one of his aerobic workouts. While there is still plenty of room, this is often in the lowest part of the amniotic sac.

Your baby's progress - Week 15

Aw – so cute! So, umm, hairy. Baby is now covered in fine hair called lanugo and will be sprouting thicker hair on her head and eyebrows over the coming weeks. The lanugo helps regulate her body temperature and grows in unique patterns like fingerprints all over her body. Most of that hair will fall out in the later weeks of pregnancy and end up being swallowed by baby as she inhales and exhales the amniotic fluid!

The tiny bones inside baby’s ears are now starting to harden and she is beginning to hear sounds, though it is unlikely she can make sense of them. Her brain’s not yet mature enough to process sound correctly, but over the coming weeks she will start to hear your digestive sounds, heart beat and voice (although it will be muffled by the amniotic fluid she’s swimming around in).

Baby now has her taste buds and some studies suggest the fetus can savour the flavour of your adult meals which contain strong ingredients like garlic – although it’s probably not as tasty for baby as the meal you have managed to eat as baby can only take in the flavours transmitted through the amniotic fluid rather than that pasta sauce! The amniotic fluid increases around your baby as she grows and moves more freely, floating like an astronaut in space.

Baby’s umbilical cord is now completely mature. The cord contains two arteries and one vein, enclosed and protected by a thick gristle-like substance called 'Wharton's Jelly'. The umbilical vein gives baby the oxygen-rich, nutrient filled blood from the placenta, with the umbilical arteries returning the depleted and deoxygenated blood back to your body.

Many of your baby's major organ systems are increasing in capacity - especially her amazing tiny heart and circulatory system.

Your baby's progress - Week 16

Baby is now around the size of an avocado and it is time to get ready for him to go through his first huge growth spurt. In the next few weeks, your baby will double his weight and finally be bigger than the placenta that is keeping him alive. Your baby's head-to-body ratio is starting to even out, as the rest of his body - including his arms and legs play catch-up.

Sometimes, when you move suddenly, you may a feel a slight pain in your sides. Ligaments on each side of your uterus and pelvic walls are stretching as baby grows. By now, baby will be making your tummy look rounder and your waistline take on the shape of a Teletubby as he will be around 12cm.

He will also be an active little demon, turning somersaults and playing with his umbilical cord. Your baby now gets the hiccups, but since they have fluid instead of air in the trachea, they do not make any sound. He also likes to play, by pulling and tugging and squeezing on the umbilical cord. Although still too slight to be felt, your baby's movements can be seen during ultrasound exams, which you will no doubt be having soon to peek at your growing bundle.

This information serves as a general guide on baby’s development cycle only, however all babies are different and develop at varying rates in the womb.

Pregnancy : 1st Trimester (2020). First trimester. Retrieved from


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