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What is Pregnancy?

What is Pregnancy?

How Do I Know If I Am Pregnant?

What's The Scientific Evidence?

What Happens in Pregnancy?

First Trimester: First Week until approx. 14 Weeks (since LMP)

Second Trimester: From approx. 14 Weeks until 27 Weeks (since LMP)

Third Trimester: From appox. 27 Weeks (since LMP) to Birth

How Will My Body Change in Pregnancy?

Your Pregnancy Rights


What is Pregnancy?

Pregnancy is the condition and time when a woman has a baby developing within her body.

A woman becomes pregnant under normal circumstances if fertilization (also called conception) occurs within her fallopian tube. The immediate result of fertilization (a process that takes place over a number of hours) is a single-cell embryo1 which is a new human organism. This new human organism is a new member of the human family, a new human being.2  

A pregnant woman carries within her body the developing and growing unborn baby for approximately 38 weeks from fertilization until birth for a full-term pregnancy or approximately 40 weeks from the first day of her last normal menstrual period (LMP).

Pregnancy therefore not only refers to the condition of a woman who is pregnant but also to gestation, which is the period of development of an unborn baby3 from the first stage of his/her existence to birth.


How Do I Know If I Am Pregnant?

You may be pregnant if you have missed your period (although this does not always indicate you are pregnant).  Changes in your body due to pregnancy may indicate you are pregnant and include feeling very tired, nausea or particularly emotional. Women may also experience 'spotting'  early in pregnancy which is not a period but light bleeding caused by implantation.  

Approximately 8 days after fertilization, cells of the growing embryo start producing a hormone called Human Chorionic Gonadotropin (hCG), which is commonly called the pregnancy hormone.  Home pregnancy tests and tests by doctors can detect hCG if it is present in your urine.  

Home pregnancy tests are widely available and you can purchase one at your local supermarket or chemist.  However, these tests are not 100% accurate, so repeat the test.  It is recommended to see a doctor or visit a pregnancy centre to confirm a pregnancy.

If you have taken a pregnancy test and it is positive, take a deep breath.  It may be a real shock to you and you may feel very scared.  You may need information and help.  The information below will fully inform you on what happens in pregnancy, how your body will change and your pregnancy rights.  Our directory may assist you to find help services in your area and you can talk with us and other people anonymously on our forums if you need to talk about your situation.  At AG, we really care about helping women who feel alone in facing their problems in pregnancy.  Please message or phone us if you are not getting the help you need.


What's The Scientific Evidence?

The scientific experts on human pregnancy are human embryologists. 

Human embryologists agree:  "Human pregnancy begins with the fusion of an egg and a sperm" 4

Fertilization is a process of fusion (joining to become one) of an oocyte (commonly referred to as an 'egg') from a woman and a sperm (spermatozoon) from a man.  

Human embryologists, O'Rahilly and Müller, say that:

 "fertilization is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is formed.."5

Another well-known human embryologist, Larsen, says that the male and female sex cells:

"unite at fertilization to initiate the embryonic development of the new individual."6  

What Does This Mean?

An oocyte and a sperm on their own are mature sex cells called gametes and are human parts, not human beings.  Once they join however, through the process of fertilization, they cease to exist and a new human organism is produced: a single-cell embryo called a zygote

Human embryologist, Moore states in an earlier edition of his textbook:   

"The zygote is the beginning of a new human being (i.e. an embryo)"7

 and in a later edition:

"Cell division, cell migration, programmed cell death, differentiation, growth, and cell rearrangement transform.. a zygote into a multicellular human being."8    

Hence sciencific evidence on human life shows that the immediate product of fertilization is an embryo, a newly existing human being.9  This human individual has his/her own unique DNA, a complete genetic code and from the first stage of existence, genetically directs his/her own growth and development as a distinct, whole human being.  

Fertilization is when the life of a human being begins.  An embryo is not a 'potential life' and does not 'turn into' a human being at a later time.  Human embryos and fetuses are human beings.  Only live, whole human beings can grow as human beings. 

The new embryo moves along the fallopian tube to implant about 6 days after fertilization into the womb (uterus), to be nourished by the mother.  From fertilization, the unborn baby develops and grows as a separate human, supported by the mother's body until birth. 

During pregnancy, the new human simply develops and grows towards maturity (adulthood).  At birth, pregnancy ends but human development continues.  Human development is a continuous process which begins at fertilization, continues through pregnancy, birth, childhood, adolesence & adulthood and only ends with death. 

Through the stages of human development, a human being changes in appearance, size, function or form, sometimes dramatically, at other times slowly.  During pregnancy the changes are phenonmenonal.  An embryo 4 weeks old doesn't look like he/she will look as a newborn, nor look the same as a newborn when he/she becomes an adult.  Yet he/she is the same individual human being.  At all times during the life of a human being, from fertilization until death, the same human individual exists.

Over the past 40 years in particular, there has been confusing information spread publicly about human life, with claims that the embryo is 'just a clump of cells' or 'just tissue' and 'not a baby'.  This misinformation has been spread widely and affects the decisions of women when it comes to abortion.  Many women have been very hurt by this misinformation when they realise later that what they aborted was not just a clump of cells but a tiny baby, even if it was very early in the pregnancy.  Women deserve to have accurate information provided to them in clear language to enable them to make an informed decision when it comes to abortion.

What Happens in Pregnancy?

The Endowment for Human Development (EHD) is an organisation which educates on pregnancy and the science of human development.  Human embryologist, Calson describes the EHD as "without question the best source of information on human embryology on the internet".10

The EHD image gallery contains pictures and videos which clearly show the growth of a new single-cell human being into a multicellular human being during the embryo and fetus development stages.

The EHD describes pregnancy as a time "for growing the parts of the body.  It is also a time of preparation for survival after birth."11  

Below, each stage is described in weeks since last menstrual period (LMP).  The actual age of the baby is approximately two weeks earlier because fertilization (when the embryo was created) occurs approximately 2 weeks after a woman's last period.  For example, the age at 6 weeks since LMP is actually 4 weeks (post-fertilization).  If a woman does not know or is unsure of the date of her last menstrual period, the only accurate way of determining the probable age of the embryo or fetus is through an ultrasound and measurements taken by a qualified clinician.  

The 9 months of pregnancy (which is actually approximately 9.5 months since fertilization and 10 months since LMP) is often divided into 3 month periods called 'trimesters'.

First Trimester: First Week until approx. 14 weeks (since LMP)

During the first trimester, the baby develops and grows dramatically from just one cell to having a highly complex body 3 inches long and resembling a tiny newborn.

Fertilization - end of 4 Weeks (since LMP)

Fertilization:  Usually occurs within several hours of ovulation but may occur up to 24 hours after ovulation.  Fertilization begins with sperm contacting the cells surrounding the ooctye and ends with the mixing of the 23 male and 23 female chromosomes, resulting in the single-cell embryo, the zygote.  

The zygote is the first cell of the body of the new human being and has a diameter of only 0.1mm.12  Sex is determined at fertilization, so the new human is already a boy or a girl.  In this week by week summary, we show footage of a tiny boy embryo so we refer to the unborn baby as a 'he'.

From fertilization until 10 weeks since LMP (or 8 weeks since fertilization) the unborn human is known as an embryo13 Embryo comes from the Greek word meaning "young one".14

2 to 4 weeks:  As the embryo moves through the fallopian tube to the woman's womb (uterus) the cells of the embryo divide repeatedly.  By the end of the third week, (approximately 6 days after fertilization) the embryo is more than twice as large and begins to embed into the wall of the womb (the uterine lining).  This is called implantation and is completed during the fourth week of pregnancy (in the second week since fertilization).15

5 Weeks - end of 6 Weeks (since LMP)

5 weeks and one day:  The heart of the embryo starts beating16 and can be seen by an ultrasound.  His brain and spinal cord are developing fast.

6 weeks:  The embryo's heart has by this time beaten more than a million times.17  By the end of 6 weeks, his head, as well as chest and abdomen cavities have taken shape and his arms and legs have started to develop, starting as little limb buds.18 Development of the brain continues rapidly.  Toward the end of this week the embryo is about half a centimetre long.  This video shows real footage of an embryo at 6 weeks since LMP (4 weeks since fertilization):


 7 Weeks - end of 8 Weeks (since LMP)

7 weeks:  By 7 weeks (5 weeks since fertilization), the embryo's brain shows all the divisions, subdivisions and cavities as seen in an infant's (young child's) brain.19 He is now about 1cm long and his face is taking shape: forehead, eyes, nostrils and mouth.20

At 7.5 weeks the embryo reflexively moves away in response to light touch on the face.21  Fingers are beginning to form on his hand.22

8 weeks:  The embryo is approximately 1.2 cm long.  Brain waves have been measured and recorded before 8.5 weeks.23

9 Weeks - end of 10 Weeks (since LMP)

9 weeks:  The embryo can move his hands and neck and may get the hiccups.24  By the end of this week, girls now have ovaries and boys have testes (testes first appear a bit earlier at 8 weeks)."25  This video shows real footage of a tiny boy at 9 weeks since LMP (7 weeks since fertilization):


10 weeks:  Kidneys begin functioning.26  The baby can urinate.   On and off, he begins making breathing motions.27  All fingers and toes are free and fully formed.28  His first hairs on eyebrow and other areas of face appear.29 He makes startle movements, general movements of his whole body,30 frequent movement of his hands and feet and may even be showing the first signs of whether he is left-handed or right-handed.31

Human embryologist, O'Rahilly:  "it has been estimated that more than 90% of the more than 4,500 named structures of the adult body become apparent during the embryonic period."32  

This means a 10 week embryo (8 weeks since fertilization) now has approximately 4,000 permanent body parts (out of the 4,500 of an adult), despite begin slightly less than 1.25 inches long.

Endowment of Human Development: "Eight weeks after conception, except for the small size, the developing human's overall appearance and many internal structures closely resemble the newborn."33

11 Weeks - end of 12 Weeks (since LMP) 

11 weeks (since LMP or 9 weeks since fertilization): From this time until birth the unborn human is called a fetus.  Fetus comes from the Latin word meaning "unborn young".34

11 weeks:   The fetus now can move his head back and forward, open and close his jaw, sigh and stretch.35  His face, palms of hands and soles of feet are sensitive to light touch.36  He starts sucking his thumb and swallowing amniotic fluid.37

11.5 weeks:  Yawning begins.38


12 Weeks - end of 13 Weeks (since LMP)

12 weeks:  Fingernails and teeth first start to grow.39  The fetus is now about 3 inches long.

13 weeks:  Lips and nose are fully formed40 and the fetus can make complex facial expresssions.41  The baby by now has taste buds all over his mouth and tongue.42  Baby is almost 4 inches long.

Second Trimester: From approx. 14 Weeks to 27 Weeks (since LMP)

14 Weeks - end of 15 Week(since LMP)

14 weeks:   Arms have reached full length in proportion to the body.43  In two weeks the fetus has grown almost two inches and is now nearly 5 inches long.

15 weeks:  The fetus now responds to light touch anywhere on his body (except on parts of the scalp).44  The woman may begin to feel the movement of the baby now.

16 Weeks - end of 18 Weeks (since LMP)

16 weeks:  The fetus is now slightly less than 7 inches long.  Slow eye movements occur. 45

17 weeks:  The baby's body starts storing body fat.46

18 weeks:  The breathing passages are complete.  If poked with a needle, the fetus releases stress hormones.47  He is now about 8 inches long.

19 Weeks - end of 21 Weeks (since LMP)

20 weeks:  The fetus now has eyebrows and head hair.48  The baby's skin becomes covered in "vernix" - a greasy white substance which protects the skin from the amniotic fluid.  He is now about 10 inches long.

21 weeks:  The baby's breathing, body movements and heart rate show the same cycles daily.49

22 Weeks - end of 24 Weeks (since LMP)

22 weeks:  The fetus can hear sounds.50  His skin and all it's structures is completely formed.51

At 22 weeks the fetus may survive outside the womb with specialised care.  In some medical centres, the survival rates of babies born this early is as high as 40%.52

23 weeks:  Rapid eye movements (REM) begin53, like those seen when children and adults have dreams (called REM sleep).

24 Weeks - end of 28 Weeks (since LMP)

24 weeks:  The baby is now about 12 inches long.  

25 weeks:  Breathing motions become more frequent.  The baby may show a blink-startle response54, such as to a sudden, loud noise.

26 weeks:  By this time the eyelids open54

28 weeks:  The baby can now smell.55  

Third Trimester: From approx. 27 Weeks (since LMP) to Birth

29 Weeks - end of 32 Weeks (since LMP)

31 weeks:  The baby looks less wrinkled as he grows fatter.

32 weeks:  His eyes can produce tears.56 

33 Weeks (since LMP) - birth

34 weeks:  Alveoli, which are "air pocket cells" start developing in the lungs.

36 weeks:  At the end of 36 weeks the baby is considered 'early term'.

37 weeks:  The baby has a firm hand grip.57  He is almost ready for birth.

38-40 weeks:  Labour starts, leading to the birth of the baby. 

 More information on each week of pregnancy can be found on an interactive timeline on the EHD website.

How Will My Body Change in Pregnancy?

Pregnancy is a natural process that a woman's body is designed to go through and usually is safe and not life-threatening for the mother.  The most common changes are listed below and afterwards a discussion of pregnancy complications that may occur.


You may experience emotional changes caused by the hormones in pregnancy and significant physical changes because your body is carrying and providing support to a rapidly growing baby, especially during the first and third trimesters.  During the first trimester, you may experience:

  • Fatigue  -  You may feel very tired during the first trimester as your body is giving nourishment to a baby growing at a dramatic rate.  
  • Nausea  -  You actually may feel 'morning sickness' (nausea) at any time during the day.  
  • Need to Urinate Frequently - You may feel the need to urinate often as early as one week after fertilization.  
  • Breast Changes - Increasing levels of hormones from the beginning of pregnancy can result in breast changes quite early.  

Changes you may experience in the second trimester may include:

  • Food Cravings or Change in Tastes - You may crave certain foods and no longer want foods you usually like.
  • Indigestion - Your digestive system will slow down which may cause bloating, constipation and coupled with your womb pushing on your stomach, heartburn.  
  • Pigmentation - May increase.  A dark line (the 'linea negra') may appear down the centre of your stomach.
  • Size - You will be noticably pregnant.  You may also gain the most weight during this trimester.

Changes you may experience in the third trimester, when the baby puts on a lot of weight to get ready for birth, include:

Shortness of breath - The size of your womb can push on your diaphragm causing shortness of breath.

Sleeping - You may need to sleep on your side or use extra pillows to get to sleep.

Skin - You may get itchy skin or stretch marks which should gradually go away after pregnancy.

Pregnancy websites, such as Essential Baby, have lots of information on pregnancy, weekly guides and health in pregnancy.  

What is most important is that you have good prenatal care (also called 'antenatal care') which involves regular checkups with a good doctor to monitor your health and the baby's health.  Usually you would visit a doctor for these visits every month until 28 weeks, then fortnightly to 36 weeks and then weekly for the last month.

Pregnancy Complications

If you live in a developed country such as the US, UK, Australia or Canada, the risk of a woman dying as a result of pregnancy complications is less than 10 in every 100,000 live births.  In poorer communities, even within the same country, as access to good prenatal and medical care decreases, the risk of dying increases.  For example, the risk for Africian-American women is 22 in every 100,000.

The most common causes of death for pregnant women are:

Emboli (blood clots affecting the heart and brain);

Eclampsia (high blood pressure complications);

Hemorrhaging (heavy bleeding);

Sepsis (infection);

Stroke or bleeding in the brain; and

Anesthesia-related deaths

Good prenatal care is essential for at-risk pregnant women to avoid injury or death in pregnancy.  Good medical treatment can treat or avoid the above conditions.  Up until late 2013, abortion was illegal in Ireland, yet Ireland had a proven track record of being one of the safest places in the world to have a baby because of it's excellent medical service and prenatal care.


Your Pregnancy Rights

It is wrong for an employer or other members of the public to discriminate against you because you are pregnant.  Laws exist in most developed countries which protect your pregnancy rights.  Examples of some laws are given below.  If laws for your country are not shown, you can do a google search on pregnancy discrimination with the name of your country, or contact the human rights commissioner or an anti-discrimination agency in your country.


In the US, the Civil Rights Act of 1964, a federal law, prohibits an employer from discriminating against an employee because of pregnancy, childbirth or related medical conditions.  Also, the Pregnancy Discrimination Act (PDA) forbids discrimination based on pregnancy regarding any aspect of employment including hiring, firing, pay, assignments, promotions, fringe benefits and any other term of employment.

In Australia the federal Sex Discrimination Act 1984 and various state acts prohibit pregnancy discrimination, not just at work but in many areas of public life, including at school and when obtaining goods or services.



1  O'Rahilly and Müller, 2001. 33; Moore and Persaud, 2013. 13, 30.

  Human being: 'An individual of the genus Homo, esp. a member of the species Homo sapiens'  http://www.thefreedictionary.com/human+being

3  Baby: 'an extremely young child; the youngest of a group' http://www.merriam-webster.com/dictionary/baby

4  Carlson, 2014. 2.

5  O'Rahilly and Müller, 2001. 8.

6  Larsen, 2001. 1.

7  Moore and Persaud, 1998.  2. 

Moore and Persaud, 2013. 1.

9   Use of the term 'human being' in science.

Human embryologists do not often refer to human embryos and fetuses in text as 'human beings' because this very general term is not useful for them to communicate with each other on human development.  They use terms such as 'zygote, blastocyst, embryo and fetus' that describe specific stages in human life and development, just in the same way that we find it helpful in everyday language to refer to a 'baby, toddler, child, teenager or adult'.  However, regardless of the terms used, general or scientific, these all refer to an existing human individual at a particular stage of development.  Every human individual is an individual member of the human species: an existing human being.

10  Carlson, 2014. Preface. vii.

11   EHD, 2014.

12  All measurements of the greatest length of the embryo and fetus used in this article are derived from:  O'Rahilly and Müller, 2001. Table A-4, 492.

13  O'Rahilly and Müller, 2001. 87.

14  From the ancient Greek word embryon - meaning 'a young one', later meaning  'that which grows'.  http://www.etymonline.com/index.php?allowed_in_frame=0&search=embryo&searchmode=none

Other sources give origin meaning as "growing within": Ayto, 1990. 

15  "The second week is characterised by implantation".  Implantation is complete by approximately 12 days.  O'Rahilly and Müller, 2001. 43 - 45.

16  "The human heart begins to beat 22 to 23 days after fertilization..":  Carlson, 2014. 433.

17  EHD, 2014Prenatal Summary.  This souce cites EHD, 2005.

18  Moore and Persaud, 2013. Fig.'s 5-9, 5-10 and 5-11. 81 - 83.

19  O'Rahilly and Müller, 2001. Fig. 19-13. 408.

20  O'Rahilly and Müller, 2001.103.

21  EHD, 2014. Prenatal Summary.  This source cites Goodline, 1979. D-128; Humphrey, 1964. 99.

22  Moore and Persaud, 2013. Table 5-1, 78. 'Digital rays' (the beginning of fingers) on the hand plates are first visible. 

23  EHD, 2014. Prenatal Summary.  This source cites Borkowski and Bernstine, 1955. 363; Hamlin, 1964. 287 and Bernstine et al. 1955.

24  EHD, 2014. Widget.  This source cites de Vries et al., 1982. 305 & 311; Visser et al., 1992. 176.

25  O'Rahilly and Müller, 2001. 320, 325.

26  O'Rahilly and Müller, 2001. 304.

27  EHD, 2014.  Prenatal Summary. This source cites Connors et al., 1989. 932; de Vries et al., 1982. 311. McCray, 1993. 579; Visser et al., 1992. 177.

28  EHD, 2014. Prenatal Summary. This source cites O'Rahilly and Müller, 1987. Figure 23-1, 260; Gasser and Cork, 2001-2011. Stage 23.

29  O'Rahilly and Müller, 2001. 169.  

30  Carlson, 2014. 458-459.

31  EHD, 2014. Prenatal Summary. This source cites Hepper et al., 1998. 531.

32  O'Rahilly and Müller, 2001. 87.

33  EHD, 2014. Prenatal Summary. This source cites O'Rahilly and Gardner, 1975. 15; O'Rahilly and Müller, 1999a. 228.

34  Online Etymology Dictionary: http://etymonline.com/index.php?allowed_in_frame=0&search=fetus&searchmode=none

35  EHD, 2014. Prenatal Summary. This source cites de Vries et al., 1982. 305-307, 311.

36  EDH, 2014. Prenatal Summary. This source cites Humphrey, 1964. 96; Humphrey, 1970. 16-17 (cited by Reinis and Goldman, 1980, 232); Humphrey and Hooker, 1959. 77-78.

37  Carlson, 2014. Major Developmental Events during the Fetal Period. Developmental Table, xii. See 9 weeks.

38  EHD, 2014. Prenatal Summary. This source cites de Vries et al., 1982. 309.

39  Carlson, 2014. Major Developmental Events during the Fetal Period. Developmental Table, xii. See 10 weeks.

40  EHD, 2014. Prenatal Summary. This source cites Timor-Tritsch et al., 1990. 291.

41  EHD, 2014. Prenatal Summary. This source cites Valman and Pearson, 1980. 234. 

42  Carlson, 2014. Major Developmental Events during the Fetal Period. Developmental Table, xii. See 11 weeks.

43  Moore and Persaud, 2003. 105.

44  EHD, 2014. Prenatal Summary. This source cites Lecanuet and Schaal, 1996. 2; Reinis and Goldman, 1980. 232.

45  Moore and Persaud, 2014. 97.

46  EDH, 2014. Prenatal Summary. This source cites Poissonnet et al., 1983. 7; Poissonnet et al., 1984. 3.

47  EDH, 2014. Prenatal Summary. This source cites Giannakoulopoulos et al., 1999. 494, 498-499; Glover and Fisk, 1999. 883; Smith et al., 2000. 161.

48  EDH, 2014. Prenatal Summary. This source cites de Vries et al., 1987. 333; Goodlin and Lowe, 1974. 349; Okai et al., 1992. 391, 396; Romanini and Rizzo, 1995. 121.

49  Moore and Persaud, 2013. 98.

50  EDH, 2014. Prenatal Summary. This source cites Glover and Fisk, 1999. 882; Hepper and Shahidullah, 1994. F81; Querleu et al., 1989. 410; Sorokin and Dierker, 1982. 725, 730; Valman and Pearson, 1980. 233-234.

51  EDH, 2014. Prenatal Summary. This source cites Pringle, 1988.180.

52  EDH, 2014. Prenatal Summary. This source cites Zayek et al., 2011. Table 1, 128.

53  Moore and Persaud, 2013. 98-99.

54  Moore and Persaud, 2013. 99.

55  EDH, 2014. Prenatal Summary. This source cites Lecanuet and Schaal, 1996. 3.

56  EDH, 2014. Prenatal Summary. This source cites Isenberg et al., 1998. 773-774.

57  EDH, 2014. Prenatal Summary. This source cites Moore and Persaud, 2003. 108.  


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