A guide through normal pregnancy

Ovulation is the time when an egg is released from an ovary. It usually occurs around 14 days after the start of the last period. In this time, multiple events are occurring: the levels of oestrogen hormones increase as the egg matures, the uterus and cervix start to produce a special mucus in preparation for arrival of sperm and the lining of the uterus grows and engorges with blood vessels to receive a fertilised egg, should conception occur. If fertilisation doesn't happen, this lining is shed as tissue and blood in the next period.

There are some physical changes that some women may be aware of at the time of their ovulation and these may include:

• Pain in the pelvic region;
• Vaginal discharge, which may resemble eggwhite;
• An increased body temperature, and;
• A heightened sense of smell, or sensitivity to odours that are not normally detected.

From sexual intercourse to fertilisation of the egg

After sexual intercourse, the uterine and cervical mucus will help to transport the sperm up into the fallopian tubes and help the sperm to survive for up to five days, in anticipation of the egg being released.

In order to fall pregnant, the timing of sexual intercourse needs to coincide with, or occur just before, ovulation and:

• It typically takes around 12-24 hours for the egg to migrate from the ovary down through the fallopian tube;
• It is within the fallopian tube that fertilisation of an egg with a sperm usually takes place;
• The egg is surrounded by thousands of sperm;
• When a sperm successfully penetrates the egg, a chemical reaction is initiated that causes a change in the egg's covering, preventing other sperm from entering, and;
• The combining of sperm and egg is called conception.

From fertilisation of the egg to implanting into the uterine wall

Within a few hours of its formation, the fertilised egg begins to divide into a series of identical cells. By the fourth day after fertilisation, it has grown into 20 cells. After this point, the cells rearrange to form a group of cells surrounded by a sac of fluid, known as a blastocyst. It continues to develop as it travels down the fallopian tube into the uterus, where it implants into the thick uterine lining.

Week 3

By this stage, the blastocyst has fully embedded into the lining of the uterus and is now connected to the mother's blood supply. This produces a hormone that prevents the mother from having her next period. This hormone is called human chorionic gonadotrophin (hCG) and detection of this hormone is what pregnancy tests are based on.

The cells within the blastocyst keep dividing and differentiating to form three distinct layers:

• Endoderm - this forms the baby's internal organs including the lungs, bowel, bladder and liver;
• Mesoderm - this forms the baby's skull, bones, sex organs, muscles and heart, and;
• Ectoderm - this forms the baby's skin, hair, eyes, spinal cord and brain.

At the same time, the outside cells of the blastocyst form two layers that are involved in the developing baby's life support system. These layers are:

• Chorion - this outer layer penetrates the lining of the uterus to obtain nourishment from the mother's blood supply. This layer will go on to form the placenta, and;
• Amnion - this inner layer becomes the amniotic sac and gradually fills with amniotic fluid.

Week 4

The blastocyst is now called an embryo and measures around 1.5mm.

The embryo at this stage has started to form the neural tube, which will become the spinal cord and the brain. It also forms a yolk sac and body stalk from the embryo's waistline. The stalk will become the umbilical cord once the placenta has fully formed (by 12 weeks). Until the placenta is ready, the yolk sac provides nourishment for the embryo - thereafter, it becomes the liver, lungs, bowel and bladder.

Some women may notice some physical changes at this stage that may include:

• Cramping and bloating in the lower part of the pelvis;
• Nausea and vomiting, or morning sickness;
• Tender breasts and sensitive nipples;
• Increased passing of urine, and;
• Slight vaginal spotting, known as implantation bleeding, from the blastocyst implanting into the uterus.

From this stage onwards, a home pregnancy test can be used to confirm the pregnancy. Upon finding out they are pregnant, many women may choose to consult their doctor. During the first visit, the doctor may carry out routine tests and a physical examination. Routine tests include hepatitis B, HIV, rubella, syphilis, urine sample, full blood count, blood group and antibodies. The doctor may also provide information regarding nutrition, folate and vitamin D dietary supplements, as well as diet and lifestyle factors that may need to be avoided.

Week 5

The embryo is around 2-4mm in length. The embryo at this stage has an umbilical cord that will supply oxygen and nutrients and remove waste. It has a primitive heart, which has already started to beat and circulate blood. This heartbeat may be detectable on ultrasound. It has also started to form feet and hands.

Some women may notice some physical changes at this stage that may include:

• Nausea and vomiting, or morning sickness;
• Feeling faint, light-headedness, fatigue;
• Lower backache;
• An increased sensitivity to smells and odours that are not normally detected or problematic;
• A feeling of fullness or heaviness in the uterus, and;
• Tender breasts.

Week 6

The embryo measures around 5-6mm by this stage. Some of the developments that commonly occur during this stage may include early development of facial features and internal organs including the oesophagus, stomach, liver, kidneys and lungs.

Some women may notice some physical changes at this stage that may include:

• Nausea and vomiting, or morning sickness;
• Increased appetite and possible food cravings;
• Tender breasts and sensitive nipples;
• Increased frequency of passing urine;
• Increased saliva production and more frequent need to swallow;
• Headaches, and;
• General abdominal distention.

The embryo may be detectable on ultrasound from this stage onwards.

Week 7

By the end of this week, the embryo will have doubled in size and may be around 1cm in length. Development at this stage comprises brain cells, more developed facial features, kidneys that are not yet functional, the pancreas, the beginnings of reproductive organs but no physical genitalia, and web-like fingers.

Some women may notice some physical changes at this stage that may include:

• Constipation;
• Nausea, vomiting and morning sickness;
• Increased saliva production and a more frequent need to swallow;
• Acne;
• Increased sensitivity to heat;
• Increased waistline, and;
• Fatigue.

Week 8

The embryo is now called a foetus and has grown to about 1.5cm in length. The foetus may have more defined fingers and toes, longer limbs, a more developed heart, a round head and developed ears, although they cannot hear sounds until around the 19^th to 24^th week.

Some women may notice some physical changes at this stage that may include:

• Nausea;
• Increased waistline;
• Fatigue;
• Lower backache;
• Increased vaginal discharge;
• Emotional changes, and;
• Bleeding gums and/or nosebleeds due to hormonal changes.

Week 9

The foetus has grown up to 2cm in length. The heart is nearly fully developed, fingers and toes are no longer webbed, head and limbs can move and the eyelids are formed but will remain closed until the 24^th week of pregnancy

Some women may notice some physical changes at this stage that may include:

• Aching legs;
• Increased vaginal discharge;
• Occasional cramps and lower abdominal pains;
• Larger and darker nipples, and;
• Acne.

Week 10

The foetus is around 3cm in length. It has a fully formed and functional liver, kidneys, intestines and brain. The foetus will also begin to show early external genitalia, a fine growth of hair over the body and have fully developed ears and eyes.

Some women may notice some physical changes at this stage that may include:

• Constipation;
• Excessive flatulence, and;
• Nausea.

It is usually around 10-16 weeks that most women will start their antenatal care, which may be in a hospital, clinic, doctor's surgery, or at home. Healthcare professionals involved in antenatal care may include a general practitioner, an obstetrician and/or a midwife.

During the first appointment, the healthcare professional will take a detailed medical history, which will enable them to set up an appropriate level of support throughout the woman's pregnancy. Also, they will take into consideration any underlying medical conditions that may affect the woman's pregnancy. A routine physical examination and blood tests will also be conducted as references for subsequent visits. The woman will be provided information about maternal serum screening (MSS) to screen for Down syndrome and related conditions and referred for these tests if requested. Information may also be provided about childbirth preparation classes, exercises, physiotherapy and dietitian services, if available and relevant to the individual's needs.

During subsequent visits, assessments will commonly be done of the woman's weight, blood pressure, abdomen and urine (for levels of sugars and proteins).

Any concerns the mother may have about her pregnancy can be addressed during these visits.

The frequency of future visits may vary depending on the health of the mother and baby. It is typical to have the next antenatal visit at around 18-20 weeks and then every 4-6 weeks for the first 28 weeks. After 28 weeks, the visits become more frequent and may take place every second week until the end of the 36^th week. From the 36^th week onwards, visits are usually weekly until the baby is born.

Week 11

The foetus is around 4-5cm in length. Most of the changes from this point onwards involve growth and maturity of the foetus's structures and organs. All the organs have been formed by this stage and the process of priming begins so that they can be ready for birth. By this stage, the genitals will have physically taken on the male or female form.

Some women may notice some physical changes at this stage that may include:

• Hair that enters a dormant phase, so that it appears thicker than normal;
• Different growth rate of fingernails, and;
• Nausea and morning sickness may start to ease.

Week 12

The foetus is around 5-6cm in length. At this stage, the foetus will begin to look more human, have functional kidneys, secrete digestive stomach juices and be able to close its hand or curl its toes.

Some women may notice some physical changes at this stage that may include:

• Skin around the nipples becoming darker;
• Easing of urination frequency, and;
• Easing of nausea and morning sickness.

Second trimester

Week 13

The foetus is around 6-7cm in length. There is a rapid growth of the body, a fully developed nose and the foetus can suckle, which will be important once born.

If the foetus is female, she will have about two million eggs in her ovaries by now. This number will drop to one million by the time she is born.

Some women may notice some physical changes at this stage that may include:

• A growing belly;
• The development of a dark line down the middle of the abdomen, called linea nigra;
• Constipation, and;
• Easing of nausea and morning sickness.

Week 14

The foetus is around 8cm in length. It may have hair starting to grow on the head, the heart may be beating in excess of 150 beats per minute, they may practise breathing the amniotic fluid in and out of their lungs and the kidneys are filtering the swallowed fluid and passing it back out as amniotic fluid.

The placenta starts producing most of the pregnancy hormones that are responsible for many of the changes the mother may be experiencing.

Some women may notice some physical changes at this stage that may include:

• Increased skin pigmentation;
• Lower blood pressure;
• Constipation;
• Metallic taste in the mouth;
• Food cravings;
• Altered libido (sex drive), and;
• Increased sensitivity to heat.

Week 15

The foetus is around 9cm in length. Some of the foetal developments include well-defined external genitalia, thumb-sucking or hiccups and legs becoming longer than arms.

Some women may notice some physical changes at this stage that may include:

• An increased appetite;
• Fatigue;
• Changes to body shape and size, such as shoe size;
• Nosebleeds, and;
• Breast enlargement.

Week 16

The foetus is around 10cm in length. At this stage, the foetus may move freely and/or start playing with the umbilical cord.

Some women may notice some physical changes at this stage that may include:

• A noticeably larger abdomen that makes the pregnancy very obvious;
• Sensitive gums that bleed easily when brushing teeth;
• Constipation;
• Altered libido;
• Increased vaginal discharge, and;
• Twinges of pain on the sides of the abdomen, caused by ligaments and muscles being stretched as the uterus grows.

Week 17

The foetus is around 13cm in length. The gender of the foetus may be detectable by ultrasound. The foetus forms fat under the skin that will provide warmth and energy once born.

Some women may notice some physical changes at this stage that may include:

• Varicose veins;
• Fatigue when standing for long periods;
• Brittle or weak fingernails;
• Altered libido, and;
• Increased sensitivity to heat.

Week 18

The foetus is around 14cm in length. Key developments include movement of the chest as the foetus mimics breathing, increased thumb-sucking and hardening of bones.

Some women may notice some physical changes at this stage that may include:

• Difficulty in finding a comfortable sleeping position;
• Altered libido;
• Feeling the foetus move around, and;
• Feeling dizzy when laying flat on the back.

Week 19

The foetus is around 15cm in length. There is formation of permanent teeth behind the already-formed milk teeth, the brain forms complex nerve connections and more hair grows on the head.

Some women may notice some physical changes at this stage that may include:

• More obvious movement of the foetus within the uterus;
• Aches and pains;
• Altered libido;
• Increased breathlessness and reduced stamina;
• Increased sensitivity to heat, and;
• Heartburn.

Week 20

The foetus is around 16cm. Eyebrows and eyelashes form, the eyes can move (although they remain shut) and the mouth can open and close.

Some women may notice some physical changes at this stage that may include:

• Their bellybutton popping out;
• Varicose veins;
• Haemorrhoids;
• Patches of darker skin on the face;
• Feeling dizzy;
• Change in their walking gait to accommodate the larger abdomen, and;
• Increased movements of the foetus within the uterus.

Week 21

The foetus is around 26cm. The foetal brain has more developed nerve connections that allow intentional movements and reactions. There is ongoing formation of waste products in the bowel, which will eventually be passed as their first bowel motion.

Some women may notice some physical changes at this stage that may include:

• Bluish or motley skin on arms and legs;
• Altered libido;
• Increased weight gain, and;
• Food cravings.

Week 22

The foetus is around 28cm. There are more fat deposits under the skin so that the foetus looks less translucent. If the foetus is female, her uterus and vagina are in place and if male, his testes descend from the abdomen down to his scrotum.

Some women may notice some physical changes at this stage that may include:

• 'Pregnancy amnesia';
• Increased breathlessness;
• Indigestion and heartburn;
• Constipation;
• Swollen ankles, and;
• Altered libido.

Week 23

The foetus is around 29cm in length. At this stage, the foetal heart is clearly visible on an ultrasound. The foetus has more coordinated movements and is able to hear and respond to loud noises. The lungs produce surfactant to help with breathing once the baby is born.

Some women may notice some physical changes at this stage that may include:

• Leg cramps, particularly at night time;
• The feeling of pins and needles in thumbs and fingers;
• Headaches;
• Increased vaginal discharge, and;
• The start of Braxton Hicks contractions.

Week 24

The foetus is around 30cm in length. There is a rapid growth in brain size, taste and touch senses are fully developed and breathing increases.

Some women may notice some physical changes at this stage that may include:

• Increased breathlessness;
• Palpitations;
• Dry eyes;
• Stretch marks forming on the abdomen, thighs, breasts or hips;
• Glands appearing as tiny bumps on areolas;
• Excessive saliva production, and;
• Headaches.

Week 25

The foetus is around 35cm in length. There is further lung development and the foetus will physically respond to touch through the abdomen.

Some women may notice some physical changes at this stage that may include:

• Swollen, bleeding gums;
• Aches and pains around abdomen, and;
• Increased appetite.

Week 26

The foetus is around 36cm in length. Some of the developments include eyes that can open and look around, awareness of noises and more frequent movements.

Some women may notice some physical changes at this stage that may include:

• Swollen ankles and fingers;
• Braxton Hicks contractions;
• Backache and sciatica;
• Fatigue and insomnia, and
• Constipation.

Week 27

The foetus is around 37cm in length. There is development of the immune system, coordination of the suck-and-swallow action and ability to distinguish light from dark.

Some women may notice some physical changes at this stage that may include:

• Increased breathlessness;
• Increased itching around abdomen;
• Insomnia;
• Rib pain and leg cramps;
• Increased weight gain;
• Increased urination;
• Swollen ankles and hands, and;
• Carpal tunnel syndrome.

Third trimester

Week 28

The foetus is around 38cm in length. The bone marrow matures enough to produce a blood supply, the liver starts to store iron and rapid eye movement sleep occurs.

Some women may notice some physical changes at this stage that may include:

• Increase in stretch marks;
• Difficulty in squatting or bending down;
• Varicose veins;
• Backache;
• Indigestion and heartburn, and;
• Swollen ankles and feet.

Week 29

The foetus is around 39cm in length. At this stage, there is increased urine output, smaller movements as the foetus becomes more cramped and further maturation of airways.

Some women may notice some physical changes at this stage that may include:

• Swollen legs, feet and hands;
• Hot flushes and increased sensitivity to heat;
• Increasingly heavier and more dense breasts;
• Darker nipples, and;
• Increased difficulty with bending over and squatting.

Week 30

The foetus is around 40cm in length. The lungs and digestive tract are nearly fully developed, more body fat is produced and there are definite sleep and wake patterns.

Some women may notice some physical changes at this stage that may include:

• Swollen ankles, legs, feet and hands;
• High blood pressure (hypertension);
• Increased breathlessness;
• Fatigue;
• Leg cramps at night-time;
• Increased urination, and;
• Braxton Hicks contractions.

Week 31

The foetus is around 41cm in length. There is ongoing foetal weight gain, fine hair disappears from the foetus's face but remains on the body and longer periods are spent in deep sleep.

Some women may notice some physical changes at this stage that may include:

• Increase in stretch marks forming;
• Increased breathlessness;
• Production of colostrum, which may leak from breasts;
• Possible depletion of iron;
• Weight gain;
• Sore rib cage and pelvis, and;
• Heartburn.

Week 32

The foetus is around 42cm in length. If the foetus is male, his testes will usually have fully descended into his scrotum. There is increased maturation of lungs and bones become stronger.

Some women may notice some physical changes at this stage that may include:

• Haemorrhoids and constipation;
• Fatigue;
• Weight gain;
• Leg cramps at night-time;
• Increased breathlessness;
• Heat rashes under breasts, and;
• Larger breasts and abdomen.

Week 33

The foetus is around 44cm in length. Most organs are fully functional and the lungs are approaching full function.

Some women may notice physical changes at this stage that may include:

• Braxton Hicks contractions;
• Urinary incontinence;
• Changes to shape of eyes and dryness may make wearing contact lenses difficult;
• Heartburn;
• Constipation, and;
• Carpal tunnel syndrome.

Week 34

The foetus is around 45cm in length. There is further weight gain and development of the immune system. It is around this stage that the foetus is nearing full development of all functions, systems and structures. There is a high chance of their survival if preterm labour occurs from this stage onwards.

Some women may notice physical changes at this stage that may include:

• Increased breathlessness;
• Difficulty finding a comfortable sleeping position;
• Heartburn;
• Indigestion;
• Varicose veins;
• Increased heat sensitivity, and;
• Altered libido.

Week 35

The foetus is around 46cm in length. The head may engage lower into the mother's pelvis in preparation for birth. Increased hiccupping of the foetus may be noticed.

Some women may notice physical changes at this stage that may include:

• Weight gain;
• Backache;
• Braxton Hicks contractions;
• Insomnia;
• Pain in the joint at the front of the two large pubic bones (symphysis pubis);
• Relief from breathlessness as their foetus engages its head lower in pelvis;
• Colostrum may be leaking from nipples, and;
• Palpitations.

Week 36

The foetus is around 47cm in length. At this stage the lungs are fully mature and further engagement lower into the pelvis may occur.

Some women may notice physical changes at this stage that may include:

• Fatigue;
• Insomnia;
• Increased frequency of urination;
• Colostrum may be leaking from nipples;
• Postural hypotension;
• Decreased breathlessness as head engages lower into pelvis, and;
• Reduced indigestion and heartburn.

Weeks 37- 42

The foetus is around 49-52cm. The foetal head continues to engage lower in the pelvis in anticipation of labour. Their growth slows down and the amount of amniotic fluid decreases. There is less room in their sac and so their movement may slow down.

By the end of week 37, the pregnancy is considered full-term and labour could start any day. A baby born between 37-42 weeks is considered full-term.

Some of the symptoms that some women may experience in the days leading up to their labour may include:

• Loss of the mucus plug that has sealed the cervix during the pregnancy;
• Loose stools;
• Weight loss;
• Nausea or vomiting;
• Increased appetite, and;
• Nesting instinct.

What actually triggers the start of labour is yet to be clearly understood. Some theories suggest it is caused by hormones that are released by the mother or baby. Another idea is that it is actually the result of chemical messages that are sent to the mother's body from the baby's brain. However none of these ideas have been proven.