Home » Follow Your Baby’s Progress » 1st trimester pregnancy symptoms

1st trimester pregnancy symptoms

Find out what to expect during the 1st trimester of your pregnancy symptoms. Below, you will find a wealth of information, which you can use as a resource.

Week 1

  1. Week 1 of pregnancy officially starts from the first day of a woman’s last menstrual period (LMP).
  1. The inner lining of the womb prepares to receive a fertilised egg between ovulation and menstruation.
  1. Dating pregnancy from about two weeks before conception helps predict the most accurate due date for an individual woman.
  1. A normal pregnancy lasts anything from 37 to 42 weeks.
  1. Pregnancy is an average of 266 days without taking the two ‘unofficial’ weeks before conception into account.
  1. When an ovum is fertilised by a sperm, 23 chromosomes from each unite.

 

Week 2

  1. The first trimester is from the start of pregnancy until 12 weeks and the busiest from baby’s developmental point of view.
  • Follicle Stimulating Hormone (FSH) is produced by the anterior pituitary gland and is responsible for maturing of the egg cell.
  1. Human Chorionic Gonadotropin (HCG) is a pregnancy hormone produced by the immature developing placenta as soon as the fertilised egg cell implants in the endometrium.
  1. HCG levels in mother’s urine and blood can confirm pregnancy with great accuracy if done at the correct time.

 

Week 3

  1. All the genetic material that will be baby’s blueprint for life is contained in the rapidly dividing ball of cells.
  1. As the cells that will become one’s baby divide, they organise themselves to perform specific tasks and become special body parts.
  1. An ultrasound scan shows rudimentary signs of pregnancy from about 3 weeks after conception.
  1. Cell division is an on-going process and soon a mulberry like cluster of almost-transparent cells, called a ‘morula’ forms.
  1. A quantitative blood test shows the pregnancy hormone HCG within 24 hours, although at this stage there is still significant room for error.

 

Week 4

  1. Some women have a distinct and intuitive feeling that they are pregnant at this stage.
  1. Some women experience bleeding much lighter than a normal period and a little earlier than expected, as a normal sign of early pregnancy, if it then passes.
  1. Blood tests give more accurate pregnancy results than urine tests and from earlier on, about 7 – 10 days after skipping menstruation.
  1. Home urine tests for HCG (human chorionic gonadotropin) to determine the likelihood of pregnancy are fairly accurate if done correctly from about 10 -14 days after skipping a menstrual period in a fairly regular menstrual cycle.
  1. The cell cluster starts to form an inner and outer group.
  1. The inner cluster will become the budding embryo, your baby-to-be.
  1. The outer group of cells become the placenta and other pregnancy support structures.
  1. The cell grouping is only about the size of a minute pin-head, but is increasing and dividing all the time.
  1. The cell cluster doubles in size every day at this stage.
  1. There are about 1,000 cells in the cluster by the end of this week.
  1. The sense of touch develops one month after conception and is crucial for brain development and emotional well-being of the unborn baby.
  1. The placenta develops by growing protrusions that imbed in the blood rich inner wall of the womb and will soon take over the vital functions to keep baby alive and thriving.

 

Week 5

  1. During this period the cell structure forms a third layer and different cells start developing differently to fulfil various, specific roles.
  1. The top layer of cells is called the neural tube and becomes the brain, the spinal cord, the nerves, and the skin.
  1. The digestive system forms from the central layer of cells.
  1. The bottom layer of cells gives rise to vital organs like the heart and to the muscles and the skeleton.
  1. The part of the embryo called the yolk sac produces blood cells but it isn’t a yolk at all.
  1. Vital body organs form and growth is rapid during this period.
  1. The eye and the inner ear develop from the same source cells.

 

Week 6

  1. Baby can easily be seen with the naked eye at this stage.
  1. A cartilage skeleton is almost complete by the end of Week Six.
  1. Baby’s sex glands have formed by this stage.
  1. Small as he is, baby can wiggle slightly now.
  1. The sense of touch develops one month after conception and is crucial for brain development and emotional well-being of the unborn baby.
  1. The breathing and digestive systems are still not differentiated and exist as a single tube.
  1. For most of the sixth week, there is no indication of protrusions that will become limbs.
  1. The buds that grow into arms will start showing by the end of this week, on the 26th day after conception!
  1. The inner structure of the lungs starts developing this week.
  1. Twins are the most common multiple pregnancy, with an incidence of about one in 90 to 100 births, with more black than white women giving birth to twins.
  1. Triplets are fairly rare at one in about 9 000 pregnancies and quadruplets, quintuplets and so on even less frequent.
  1. Multiples, other than twins, are nowadays more often than not the result of fertility drugs, occurring very rarely naturally.
  1. By the end of Week 6, the embryo is 4 millimeters long.
  1. Baby’s heart is about 2 millimeters from top to bottom and can be seen beating on ultrasound between six and eight weeks.
  1. The embryo lies curved, already hinting at the well-known foetal position, just like a small apostrophe.

 

Week 7

  1. Pregnancy can only be confirmed on an ultrasound scan at about 6-8 weeks after conception.
  1. The embryo grows from about 5 millimeters to about 8 millimeters long during the course of this week.
  1. While baby’s arms continue to develop during this week, leg buds also emerge.
  1. Baby almost doubles in length this week.
  1. Folds of tissue can be noticed on the head will become chin, cheeks and ears.
  1. The main air pipe called the trachea and the gullet or oesophagus now begin to separate into two distinct tubes.
  1. The heart does not yet have compartments but has already begun to beat.
  1. The brain was the first organ to develop and in this week alone has increased in size by 25 percent.
  1. Baby’s rudimentary hands look like paddles.
  1. Baby appears to have a tail but this is an extension of the spine that will disappear.
  1. Baby’s head almost touches the foot end, so strong is the curvature of the embryo at this stage.
  1. At this stage the mouth is just a hollow in the head.
  1. The most developed organs are the brain and the heart at this stage.

 

Week 8

  1. Until eight weeks baby is known in medical terms as an embryo.
  1. From eight weeks on baby’s medical name is foetus, which means ‘offspring’ or ‘young one’.
  • Major organs like the heart have now formed and start primitive functioning.
  • Baby is essentially a complete little human being at this stage.
  • Baby is only the size of a small apricot.
  1. The head is now about half the length of baby’s body and baby’s forehead bulges prominently.
  1. At birth the head will be one quarter of baby’s total body length.
  1. The upper and lower jaws form this week.
  1. The first hint of eyes can now be seen at the sides of the head.
  1. At this stage of development baby’s eyes are disproportionately large to the head.
  1. Just imagine, delicate structures like the tear ducts are now forming close to the eyes.
  1. By the end of this week, baby sprouts a slight bulge on the face that will become the nose.
  1. Shell-like outer ears now develop, emerging from low on the head.
  1. Baby’s sense of hearing develops from about 20 weeks, despite having outer ears now.
  1. As the head grows in coming weeks, the ears and eyes will seem to move to their appropriate positions.
  1. Baby’s milk teeth start forming in sockets in the jaw.
  1. Bone marrow cells are made at this stage in preparation for manufacture of blood cells.
  1. Baby’s bone marrow cells which are made now form a vital part of baby’s immune system.
  1. Baby weighs between 3 and 5 grams at the end of Week 8.
  1. The embryo grows from about 9 millimeters at the beginning to about 11 to 13 millimeters long by the end of this week.
  1. Arms and legs grow rapidly during this stage.
  1. The paddle-like shapes at the end of the upper limbs now begin to look like hands but the fingers are very stubby.
  1. The kidneys begin to develop this week.
  1. The digestive tract continues to grow rapidly this week.
  1. The abdomen is too small for the whole intestine which protrudes a little into the base of the umbilical cord.
  1. Muscles begin to form around the skeleton.
  1. The skeleton is still of cartilage, not bone.
  1. Joints have formed now too.
  1. Newly formed fingers and toes appear webbed at this stage.
  1. Lips begin to form this week and give baby a distinctly human appearance, but mouth and nose openings are still a single cavity.
  1. The heart has developed two chambers from the single tube and will eventually have four.

 

Week 9

  1. Baby is about 14 millimeters long at the beginning of this week and can grow to 22 – 28 millimeters by the end of the week.
  1. The legs are bent at an angle so that the soles of the feet face each other.
  1. The cartilage skeleton now systematically begins to be replaced by bone cells.
  1. Although bones are now forming, they don’t harden until shortly before birth and are still pliable afterwards.
  1. The gallbladder begins to form this week.
  1. The arm starts to bend slightly at the elbow.
  1. Baby’s tongue is developing inside the mouth.
  1. Baby’s head appears rounder than in previous weeks and is held almost upright at this stage.
  1. Eyes appear to have moved closer to each other this week.
  1. Toes start appearing at the end of the feet this week.

 

Week 10

  1. Physically male and female foetuses look alike for a number of weeks, as the testes are located in the same place in the pelvic cavity as the ovaries are.
  1. The genitalia are still very immature at this stage.
  1. From the point of DNA and the chromosomes, the differences between the genders are there from conception already.
  1. The heart is all but fully developed now and all four chambers are present.
  1. Baby’s heart now beats strongly, although function is still not as it will be after birth.
  • Baby’s heartbeat will show clearly on a scan by now and looks like a flashing asterisk on the screen.
  • A baby’s heartbeat in pregnancy varies between 120 and 140 beats a minute.
  1. Baby’s fingers and toes are still webbed.
  • Baby weighs about 8 grams and is about 2.5 or 3 cm long.
  1. Baby’s eyes are well-formed.
  1. Baby’s eyelids now begin to form.
  1. Pigmentation is now forming in the eye.
  1. The tip of baby’s nose is now quite distinct.
  1. Olfactory organs that are responsible for the sense of smell develop by the second month of gestation.
  1. Taste buds have formed at this stage.
  1. The liver begins to produce red blood cells during this week.
  1. Major blood vessels develop as an important part of the circulatory system.
  1. Fingers are more distinct, but still stubby.
  1. Brain waves register on an electro-encephalogram (EEG) at this stage.
  1. The whole ear, inner, middle and external, are formed, but not yet in their final positions.
  1. Muscles in the trunk, limbs, and head are developing rapidly this week.
  1. The large muscles of baby’s body are now capable of contracting.
  1. Baby is still termed an embryo, but looks increasingly human.
  1. Baby is about the size of a strawberry at this stage.

 

Week 11

  1. Baby has doubled in size over the past four weeks.
  1. The liver is quite large, making up 10% of complete body weight.
  1. Foetal blood circulation is responsible for removing waste products from the developing baby.
  1. This is the stage when the formation of the palate is completed.
  1. Baby’s fingers cannot yet move individually.
  1. Fingernails begin to form at the tips of baby’s fingers now.
  1. Baby’s head is becoming more round but growth slows down a bit now.
  1. Baby’s head is almost half the complete body size at this stage.
  1. Baby’s body now begins to grow in proportion to the head.
  1. The finishing touches to baby’s tongue are done this week.
  1. All rudimentary sockets for adult teeth are already forming below the milk teeth in baby’s jaw bone.
  1. The intestine rotates and moves into position in the abdomen.
  1. The diaphragm forms, separating the chest from the abdomen.
  1. Baby is now 5 cm in length and weighs 14grams on average.

 

Week 12

  1. Baby’s heart pumps blood throughout the body and most other organs have started primitive functioning.
  1. Baby’s face is distinctly human by now, his eyes are fully formed and he can scrunch his face.
  1. There is basic co-ordination between brain activity and limb movement and baby moves quite strongly, although you can’t yet feel this.
  1. Toes and fingers are now complete.
  1. Vocal chords are now formed.
  1. Baby’s hair follicles develop at this stage.
  1. The tear ducts are completed now.
  1. Baby’s external genitalia form around now.
  1. Your perfect but skinny baby swallows amniotic fluid in the womb.
  1. At the end of the all-important first trimester, baby is about 8cm long and weighs about 45grams.
  1. Medically speaking, after Week 12, the term ‘foetus’ is used for your developing baby.
  1. All organs and systems found in a full-term newborn are now present.
  1. Structure and function of organs and body systems still require much growth and maturing.
  1. Baby is surrounded by about 50 cubic cm of amniotic fluid at this stage.
  1. Baby’s heartbeat can be heard with an ultrasonic Doppler device at this stage.
  1. The irises of the eyes develop at this stage.
  1. The pancreas is now manufacturing digestive enzymes and insulin.
  1. Baby’s metabolism is regulated by the thyroid gland which has begun to function on its own now.
  1. Chest movements that prepare baby for breathing after birth begin now and continue throughout pregnancy.
  1. Baby’s swallowing reflex starts.
  1. The lungs are beginning to develop more fully.

 

Week 13

  1. The second trimester of pregnancy stretches from week 13 to week 28 and is often called the honeymoon phase because many of the early niggles and discomforts have passed.
  1. Baby is now about 9 cm long on average.
  1. The average 13 week developing baby weighs between 55 and 60 grams.
  1. Baby makes sucking motions now.
  1. One notices posture changes in baby as more muscles develop and the skeleton becomes stronger, helping hold the baby more upright.
  1. Independent hormone production is now possible while until now baby’s endocrine requirements have been produced by the mother.
  1. Baby now stretches and exercise its arm and leg muscles.
  1. Baby’s upper limbs are completed first, the arms before the legs, the hands before the feet and the fingernails before the toenails.
  1. The legs are less well developed and consequently weaker than the arms at this stage.
Copyright 2012 Sister Lilian







Wondering what to expect and when?

Many find it easy to work out how the weeks, months and trimesters relate to each other. Click a week, a month or trimester below to see what your little one will be doing in your 'bump' at that stage.

1st Trimester 2nd Trimester 3rd Trimester
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Month 1 Month 2 Month 3 Month 4 Month 5 Month 6 Month 7 Month 8 Month 9
 *This is just a guideline and the exact weekly breakdown may differ from source to source.