Pregnancy 101

Things are really moving now, fingers and toes are starting to separate (previously they looked like webs), bones @ are hardening, vocal cords are forming, the digestive system can even push food through.

Following your baby’s development as it grows in your womb can be an exhilarating experience. Knowing that what is growing inside you has, for example, eyes that can open and ears that can hear can help you not only establish a bond with the little soul within, but also come to terms with the fact that you are pregnant and that some time soon, you will have a baby.

Don’t forget, however, that every pregnancy is different and every baby is unique, so the following stages of pregnancy are just a very general look at how a baby develops and what that may mean for you. Many women stress needlessly if they, for example, don’t feel their baby moving around at 18 weeks; some women even worry if they don’t experience morning sickness, thinking something must be wrong. Always raise your concerns with your healthcare practitioner, but remember that how your pregnancy is developing is right for you and is no better or worse than the pregnancy your neighbour’s sister’s friend is experiencing!


First trimester


Week 1

Pregnancy is typically calculated from the first day of your last period, but technically you are not pregnant this week. What is happening is that you finish your period and then move into the follicular phase of your cycle, in which 15 to 20 eggs start to mature in each ovary. Each egg is encased in its own follicle (a tiny sac) and the follicles produce oestrogen, which helps the egg to mature. This maturation process can take from eight days to one month.

Week 2

Technically, you are still not pregnant this week. If your eggs have matured at the end of the week you may be ready to ovulate. This means the largest follicle releases an egg from one ovary which then travels along the fallopian tube. The ovaries also release progesterone at this time to prevent the release of the other eggs and to start building up the uterine lining. (Occasionally, two eggs will be released, resulting in twins.) Progesterone also cause three primary fertility signs to change: your temperature will slightly alter, your vagina will produce a clear, stretchy mucus that looks like an eggwhite and your cervix will rise, soften and open.

Week 3

The egg remains alive in the fallopian tube for 24 hours, however it usually needs to meet a single sperm in the fallopian tube within a few hours of ovulation for fertilisation to take place, and when it does — congratulations, you are pregnant! Sperm can actually live in a woman for up to five days if the conditions are right, so it is actually possible to have sex on a Saturday and not fall pregnant until the Wednesday when you ovulate. The fertilised egg (zygote) then takes about a week to travel down the fallopian tube, rapidly dividing and growing as it does, until it arrives in the uterus. Here it implants into the uterine lining and splits into two sets of cells; one set will become the placenta and the other will become the foetus. At this stage you will start releasing a pregnancy hormone known as HCG. Pregnancy tests look for the presence of this hormone.

Week 4

Every day, your baby continues to grow rapidly and pregnancy symptoms can often kick in at this time (sometimes earlier), including frequent urination, swollen breasts, constipation and morning sickness. Morning sickness (which could be also known as any-time-of-the-day sickness) is due to a range of factors such as high levels of HCG and oestrogen, a fall in blood pressure and altered senses.

Week 5

Your baby is now called an embryo and is about 1.5mm. The embryo looks like a cylinder. The top end of the tube starts to enlarge to form the beginning of the baby’s brain. At the end of this week your baby develops a primitive heart, shaped as a long tube, which begins beating.

Week 6

The embryo, which now resembles a tadpole and is approximately 5-10mm, continues to grow very rapidly. The digestive tract, facial features, thyroid, lungs, liver and pancreas begin to take form and tiny buds appear, which will turn into arms and legs.

Week 7

Eyes and ears are starting to form and the arm and leg buds protrude more. The brain has divided into distinct segments and the heart becomes a four-chambered organ. The sex organs are almost fully formed and the pancreas is present. You may have started experiencing extreme tiredness, caused by a variety of factors such as an increased metabolic rate and high levels of progesterone.

Week 8

This week, many of the organ systems are reaching their final stages of development; from now on they just get bigger in size.

Week 9

Your growing embryo is starting to look more like a baby. It now measures about 2.5cm. You may experience light-headedness at this time as your blood pressure may have decreased and your face may seem slightly fuller due to fluid retention.

Week 10

Your baby is now referred to as a foetus, which means "offspring". It is sprouting 20 tiny tooth buds and has a responsive nervous system. Its heart has reached its final shape and now beats at about 140 beats per minute.

Week 11

At this time, your baby has short sleep-wake cycles which last about five to 10 minutes. Irises are starting to develop and your baby can swallow, yawn and suck. HCG levels are at their peak this week.

Week 12

Things are really moving now. Fingers and toes are starting to separate (previously they looked like webs), bones are hardening, vocal cords are forming, the digestive system can even push food through.

Week 13

Your belly may be starting to swell about now and your morning sickness may have subsided. You may even have more energy. Your baby now measures about 7cm from head to bottom and its kidneys and liver have started to work.


Second trimester

Week 14

Your baby can now bend and flex its fingers, hands, toes, legs and knees as its nervous system begins to function.

Week 15

Very fine hair, called lanugo, is starting to appear on your baby’s skin; this helps it to regulate body temperature. It is also growing eyebrows and hair on its head. Facial muscles are also sporadically active, so your baby can now squint and frown.

Week 16

Your baby now measures just over 10cm from head to bottom and weighs about 80g. Its arms and legs are complete, all its joints are working and the nervous system is fully operational, so it can co-ordinate all its movements. This is an active time for your baby and if you have had a baby before, you may detect its movements.

Week 17

Your uterus is now growing rapidly and you may feel occasional pain in your lower abdomen and groin as your muscles and ligaments stretch. Your baby has begun to practise breathing movements as it inhales and exhales amniotic fluid.

Week 18

By now a female foetus’s ovaries have already developed follicles that hold all the eggs she will ever have, but these eggs won’t develop to the point of ovulation until puberty. If your baby is a boy, his prostate will be forming. Pads have formed on your baby’s fingertips and toes and unique swirls that will become its fingerprints are starting to appear.

Week 19

Your baby now weighs approximately 200g and is approximately 14cm from head to bottom. Myelin starts coating and insulating your baby’s nerves, allowing the smooth, rapid exchange of information. Buds which will become permanent teeth also start to form.

Week 20

You are technically halfway through your pregnancy, though 80 per cent of first babies come late and babies can, of course, come early. This is an important time for the development of your baby’s senses — touch, smell, hearing and sight — as the brain is developing specialised areas for these. You will probably start feeling the baby move.

Week 21

Your baby now weighs about 300g, which is about 10 per cent of its final birthweight. A substance called meconium begins to accumulate in your baby’s bowel. This is a mixture of digestive secretions and swallowed amniotic fluid. It looks like black tar and will be your baby’s first poo.

Week 22

If you are having a boy, his testes have started to drop from his pelvis to his scrotum and primitive sperm begin to form. If you are having a girl, her uterus and ovaries are in place and the vagina is developed. Your baby can now hear noises such as loud conversations and music. Sweat glands are also developing and the external skin has turned from transparent to opaque.

Week 23

The pigment that colours your baby’s skin is being deposited this week. Your baby looks wrinkled as the skin is produced more quickly than the fat accumulates. Internally, the pancreas is developing; this will supply insulin, which is a vital hormone for laying down fat.

Week 24

This week, with expert care, your baby has about a 50 per cent chance of survival outside the uterus. Your baby’s inner ear is now completely developed and as it controls balance, your baby is able to tell whether or not it is upside down.

Week 25

Your baby now weighs about 700g. If your baby were born now it would have about a 70 per cent chance of surviving. Most of your baby’s organs are well developed except its lungs and digestive tract.

Week 26

The lungs of your baby are still maturing and it’s still growing and gaining more fat and muscle. If your baby were born now it would have about an 80 per cent chance of surviving. Its spine is getting stronger and it has fingernails, eyebrows and eyelashes. Your baby also responds to touch at this time and can recognise voices other than your own.

Third trimester

Week 27

Your baby now weighs about one kilogram. Its eyelids, which were previously fused, can now open some of the time. Your baby also has fully functioning tastebuds.

Week 28

The skin of your baby is now completely covered by vernix, a waxy protective coating. The foetus is now entering its maximum growth phase in length and also weight. Babies are also known to hiccup at this time.

Week 29

Your baby now weighs about 1.6kg and you’re also carrying around the placenta and about one litre of amniotic fluid, so you may be experiencing some discomfort. You may also be experiencing shortness of breath as the growing uterus pushes up into your diaphragm. The brain of your baby is developing rapidly and it can now control breathing and body temperature.

Week 30

Somewhere between the 28th and 32nd week your baby’s brain will be as advanced as a newborn’s and it’s therefore able to feel and remember. The lanugo that covered its body begins to disappear and the hair on your baby’s head becomes thicker. If your baby were to be born now it would have a 90 per cent chance of survival.

Week 31

Your baby now weighs approximately 2kg and measures 39cm. It continues to put on weight and its brain keeps developing connections.

Week 32

All your baby’s senses are now fully developed and it can see, hear, smell and touch. The foetus sleeps about 95 per cent of the time and rapid eye movement (REM), which is associated with dreaming, can be detected. If born now, your baby will almost certainly survive.

Week 33

The head of your baby may be now just above your pelvis, so you may feel kicks into your ribs. Your baby has started to store iron, calcium and phosphorus, which are important for bone development. It is starting to make rhythmic breathing movements but its lungs still aren’t fully matured.

Week 34

Your baby can now recognise a particular piece of music and co-ordinate its movements in time with it. Mozart is found to be especially enjoyable for a baby.

Week 35

The length of your baby from head to bottom is now approximately 37cm and it weighs about 2.5kg. Its lungs, nervous system and digestive system are nearly fully developed.

Week 36

Your baby continues to put on weight, but is nearing the end of its maximum growth stage. Its kidneys are now fully developed and its liver is processing some wastes.

Week 37

You may not feel your baby move as much now, as it doesn’t have much space to do so. Your baby’s immune system and brain continue to develop and your breasts may have started to produce colostrum, which could occasionally leak.

Week 38

Your baby is now clinically mature and can be born at any time. All its organs and systems are fully developed. You may feel the foetal head "engage" in the pelvis at this time, usually accompanied by a feeling of increased pressure on your pelvic floor.

Week 39

Your cervix gets softer in preparation for childbirth. Your baby’s growth slows down in preparation for birth. Boys are usually slightly heavier than girls by an average of 100g.

Week 40

Your baby is now "due" but if this is your first child chances are it will come a little late. Your baby’s skin is now smooth and has lost most of the fine lanugo hair. Its skin is still covered by vernix, which will keep the baby warm after delivery and will also facilitate the birth process. @BC2:After your baby is born, it may have some typical newborn features such as a puffy face, bruised eyes, a head that looks elongated, jaundice, small white spots on its face, red blotches and other types of birth marks. If you have your baby in a hospital, a paediatrician will review your baby’s health and then it’s time for lots of love and bonding.

Did you know?

Women are fertile only a few days per cycle, so if you are trying to fall pregnant or know of someone who is, it may be worth looking into Fertility Awareness Management (See Taking Charge of Your Fertility by Toni Weschler, Quill 2002) to help understand your cycle and maximise these fertile times.

The WellBeing Team

The WellBeing Team

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