An average pregnancy is counted as 40 weeks, as it is counted from the first day of the mother's last period.
Pregnancy is divided into three trimesters:
The development of the unborn baby can be followed week by week, but pregnancy is different for every woman and their baby. The following week-by-week summary is a guide only and women may experience different feelings and/or symptoms at other times than those suggested.
Your doctor will advise you about the progress of your pregnancy.
The first day of pregnancy is counted as the first day of a woman's last period. This is how the expected due date is calculated, i.e., 40 weeks from the first day of the last period.
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 estrogen 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 fertilized egg, should conception occur. If fertilization 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:
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:
Within a few hours of its formation, the fertilized egg begins to divide into a series of identical cells. By the fourth day after fertilization, 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.
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:
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:
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:
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.
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:
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 esophagus, stomach, liver, kidneys and lungs.
Some women may notice some physical changes at this stage that may include:
The embryo may be detectable on ultrasound from this stage onwards.
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:
The embryo is now called a fetus and has grown to about 1.5cm in length. The fetus 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 19th to 24th week.
Some women may notice some physical changes at this stage that may include:
The fetus 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 24th week of pregnancy
Some women may notice some physical changes at this stage that may include:
The fetus is around 3cm in length. It has a fully formed and functional liver, kidneys, intestines and brain. The fetus 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:
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 36th week. From the 36th week onwards, visits are usually weekly until the baby is born.
The fetus is around 4-5cm in length. Most of the changes from this point onwards involve growth and maturity of the fetus'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:
The fetus is around 5-6cm in length. At this stage, the fetus 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:
The part of the body that lies between the chest and the pelvis.
The fluid surrounding and protecting the fetus inside the uterus during pregnancy.
The bag that develops in the uterus during pregnancy, in which the fetus develops.
A protein molecule produced by the immune system. Antibodies bind specifically to foreign substances to neutralize them or target them for destruction.
The pressure the blood places on the walls of the arteries, largely mirroring the contraction of the heart, and consisting of two readings. The higher reading is systolic blood pressure, when the heart contracts, and the lower is diastolic blood pressure, when the heart is relaxed.
The fundamental unit of life; the simplest living unit that can exist, grow, and reproduce independently. The human body is composed of trillions of cells of many kinds.
The lower part of the uterus, leading out into the vagina.
Difficulty emptying the bowels, usually associated with hard, dry feces.
Present but currently inactive.
The tube-like structures connecting a woman's uterus to her ovaries. Eggs released by the ovaries travel to the uterus via the fallopian tubes.
A state of exhaustion and weakness.
An unborn human, from the ninth week of pregnancy until birth.
A blood test that examines the blood, either by using a microscope or an automated machine, to determine the number of red blood cells, white blood cells and platelets.
A virus transmitted mainly by sexual or blood-to-blood contact, that infects cells of the immune system. It is the causative agent of acquired immune deficiency syndrome (AIDS).
A chemical substance secreted in one part of an organism and transported to another part of that organism, where it has a specific effect.
A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.
Also called the gullet or food pipe, it is the muscular tube connecting the throat and stomach. It is lined with a mucous membrane. After ingestion, food and drink travel down the esophagus to be digested in the stomach.
One of a group of steroid hormones involved in the development and maintenance of female sex characteristics. These are the primary female sex hormones.
An organ located behind the stomach that secretes insulin and glucagon into the bloodstream and digestive enzymes into the intestines.
The bony structure in the lower part of the body trunk that connects the base of the spine to the legs. The pelvis protects important organs, such as the bladder and bowel (and in women, the uterus), and anchors thigh and abdominal muscles.
The organ that forms within the uterus of a pregnant woman to provide the fetus with nourishment from the blood supply of the mother.
The mature male sex cell that fertilizes the female ovum.
Also called the birth cord. A tube connecting the blood supply of the uterus of the mother to the circulatory system of the developing baby.
The hollow organ of the female reproductive system that is responsible for the development of the embryo and fetus during pregnancy. Also known as the womb.
The fluid that a healthy vagina secretes to cleanse and regulate itself.
Relating to the pelvis, which is the bony structure in the lower part of the trunk. The pelvis connects the base of the spine to the legs, anchors the thigh and abdominal muscles and protects important organs such as the bladder and bowel (and in women, the uterus).
Relating to the abdomen, the middle portion of the trunk which contains organs such as the intestines, stomach and liver.
A vitamin that is important for the health of bones and teeth as it promotes absorption of calcium from the diet.
Relating to hormones, which are chemicals secreted in one part of an organism and transported to another part of that organism, where they have a specific effect.
A sexually-transmitted bacterial infection that causes sores and skin rashes. If left untreated, it can affect the brain and heart.
A contagious viral infection characterized by fever, enlargement of lymph nodes and a widespread red rash. Also known as German measles.
Liver inflammation caused by the hepatitis B virus, which is spread via blood, sexual fluids and through the placenta.
A blood test that identifies whether a pregnant woman is at an increased risk of having a baby with Down syndrome, trisomy 18 or neural tube defects.
The fetus is around 6-7cm in length. There is a rapid growth of the body, a fully developed nose and the fetus can suckle, which will be important once born.
If the fetus 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:
The fetus 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 practice 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:
The fetus is around 9cm in length. Some of the fetal 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:
The fetus is around 10cm in length. At this stage, the fetus may move freely and/or start playing with the umbilical cord.
Some women may notice some physical changes at this stage that may include:
The fetus is around 13cm in length. The gender of the fetus may be detectable by ultrasound. The fetus 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:
The fetus is around 14cm in length. Key developments include movement of the chest as the fetus mimics breathing, increased thumb-sucking and hardening of bones.
Some women may notice some physical changes at this stage that may include:
The fetus 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:
The fetus 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:
The fetus is around 26cm. The fetal 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:
The fetus is around 28cm. There are more fat deposits under the skin so that the fetus looks less translucent. If the fetus 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:
The fetus is around 29cm in length. At this stage, the fetal heart is clearly visible on an ultrasound. The fetus 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:
The fetus 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:
The fetus is around 35cm in length. There is further lung development and the fetus will physically respond to touch through the abdomen.
Some women may notice some physical changes at this stage that may include:
The fetus 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:
The fetus 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:
The part of the body that lies between the chest and the pelvis.
The fluid surrounding and protecting the fetus inside the uterus during pregnancy.
The pressure the blood places on the walls of the arteries, largely mirroring the contraction of the heart, and consisting of two readings. The higher reading is systolic blood pressure, when the heart contracts, and the lower is diastolic blood pressure, when the heart is relaxed.
Short and non-rhythmic uterine contractions during pregnancy that are not associated with labor contractions. They can occur as early as 16 weeks into pregnancy.
Difficulty emptying the bowels, usually associated with hard, dry feces.
A state of exhaustion and weakness.
An unborn human, from the ninth week of pregnancy until birth.
Any organ of the body that secretes substances, such as hormones or enzymes, that are used by other parts of the body.
Stomach pain or discomfort caused by difficulties digesting food.
One or more fibers that transmit signals of sensation and motion between the brain or spinal cord and other parts of the body.
The organ that forms within the uterus of a pregnant woman to provide the fetus with nourishment from the blood supply of the mother.
The pouch of skin that contains the testicles; relating to the scrotum.
The male sex organs located in the scrotum that produce sperm.
Also called the birth cord. A tube connecting the blood supply of the uterus of the mother to the circulatory system of the developing baby.
The hollow organ of the female reproductive system that is responsible for the development of the embryo and fetus during pregnancy. Also known as the womb.
The fluid that a healthy vagina secretes to cleanse and regulate itself.
A twisted and enlarged vein that is near the surface of the skin or other organ.
A pounding or racing heart sensation, which can be associated with both normal and abnormal heart conditions.
The burning sensation or discomfort in the chest caused by regurgitation of food or acid from the stomach into the esophagus (the food pipe). Also known as gastric reflux.
A slight loss of memory during pregnancy and, in some cases, after the birth.
The pink or brownish ring of tissue around the nipple.
The fetus 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:
The fetus is around 39cm in length. At this stage, there is increased urine output, smaller movements as the fetus becomes more cramped and further maturation of airways.
Some women may notice some physical changes at this stage that may include:
The fetus 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:
The fetus is around 41cm in length. There is ongoing fetal weight gain, fine hair disappears from the fetus'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:
The fetus is around 42cm in length. If the fetus 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:
The fetus 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:
The fetus is around 45cm in length. There is further weight gain and development of the immune system. It is around this stage that the fetus is nearing full development of all functions, systems and structures. There is a high chance of their survival if preterm labor occurs from this stage onwards.
Some women may notice physical changes at this stage that may include:
The fetus is around 46cm in length. The head may engage lower into the mother's pelvis in preparation for birth. Increased hiccupping of the fetus may be noticed.
Some women may notice physical changes at this stage that may include:
The fetus 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:
The fetus is around 49-52cm. The fetal head continues to engage lower in the pelvis in anticipation of labor. 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 labor 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 labor may include:
What actually triggers the start of labor 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.
The part of the body that lies between the chest and the pelvis.
The fluid surrounding and protecting the fetus inside the uterus during pregnancy.
The pressure the blood places on the walls of the arteries, largely mirroring the contraction of the heart, and consisting of two readings. The higher reading is systolic blood pressure, when the heart contracts, and the lower is diastolic blood pressure, when the heart is relaxed.
The spongy, vascular or fatty tissue found inside bones, responsible for producing blood cells.
Short and non-rhythmic uterine contractions during pregnancy that are not associated with labor contractions. They can occur as early as 16 weeks into pregnancy.
The lower part of the uterus, leading out into the vagina.
The secretion of milk produced by the mammary glands for the first few days after giving birth. It is rich in antibodies.
Difficulty emptying the bowels, usually associated with hard, dry feces.
The series of organs within the body that contribute to the digestion of food. It begins at the mouth and ends at the anus, and includes the stomach, small and large intestines as well as the pancreas, gallbladder and liver.
A state of exhaustion and weakness.
An unborn human, from the ninth week of pregnancy until birth.
Low blood pressure.
The uncontrollable loss, small or large, of bladder or bowel control, resulting in leakage of their contents.
Stomach pain or discomfort caused by difficulties digesting food.
An essential mineral required by the body. Iron is part of a protein in the blood called hemoglobin, which carries oxygen around the body.
Signals the end of a pregnancy and the process of giving birth to a baby from the uterus to the outside world.
A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.
The bony structure in the lower part of the body trunk that connects the base of the spine to the legs. The pelvis protects important organs, such as the bladder and bowel (and in women, the uterus), and anchors thigh and abdominal muscles.
The pouch of skin that contains the testicles; relating to the scrotum.
The male sex organs located in the scrotum that produce sperm.
A twisted and enlarged vein that is near the surface of the skin or other organ.
A pounding or racing heart sensation, which can be associated with both normal and abnormal heart conditions.
The burning sensation or discomfort in the chest caused by regurgitation of food or acid from the stomach into the esophagus (the food pipe). Also known as gastric reflux.
The two joined bones that form the lower front part of the hipbone in the pelvis (groin).