Terminology from conception to birth 

1st: Zygote  

2nd: Blastocyte 

3rd: Embryo 

4th: Foetus   

5th: Infant  


The Prenatal Period is the time between conception and birth: 


Three stages 

1) Germinal stage (2 weeks) 

2) Embryonic stage (6 weeks)  

3) Foetal stage (7 months) 


Stage 1: The Germinal Stage (2 weeks)    


1st: conception occurs when a sperm cell combines with an egg cell to form a Zygote.   


2nd: (around 36 hours after conception), the zygote divides quickly, forming a cluster of cells known as a blastocyte. The blastocyte travels along the fallopian tube towards the uterus.   


3rd (around 7 days after conception), the blastocyte becomes embedded in the wall of the uterus = this process is known as implantation and takes about a week to complete. If implantation fails, the pregnancy terminates.  


Another significant feature of the germinal stage, is the formation of the placenta. The placenta acts as a filter between the circulatory systems of the mother and baby (embryo). Two important functions of the placenta include:   

It provides the growing embryo with oxygen and nutrients (food) from the mother's blood  

It also removes waste materials from the embryo, to be excreted via the mother's excretory organs (lungs, kidneys, bowel).  


Stage 2: The Embryonic Stage (6 weeks)   


 The blastocyte (cluster of cells) is now called an Embryo.


In this stage, all the major organs (GIT, spinal cord, brain and heart) and membranes begin to develop (no bones nor muscles).  

The greatest danger during this stage are teratogens (viruses, alcohol, drugs and radiation) and nutrient imbalances (excess and deficiency). Both teratogens and nutrient imbalances can cause growth deformities. 


Stage 3: The Foetal Stage (7 months)   


About one month into this stage, the sex organs, bones and muscles begin to form and preformed organ systems develop further and start to function.  


The sex of a foetus is determined by genes (genetic material passed on from parents to offspring), located on chromosomes. There are two different types of sex chromosomes: X and Y. Females have two XX chromosomes and males have both a X and Y chromosome. In early development all foetus genitalia (sex organs) are expressed as female. After about 6-7 weeks, the expression of a gene on the Y chromosome induces changes which results in the development of the male testes. At 9 weeks, the production of testosterone, causes further masculinization of the reproductive tract and brain.


The foetus begins to move, suckle and swallow inside the uterus.  


The middle ear develops which allows the foetus to hear the mother's heartbeat and voice. 


The foetus is surrounded in darkness but can detect bright lights from outside the womb.  


Three significant developments occur during the last three months of this stage:  

The brain rapidly increases in size 

An insulating layer of fat forms under the skin 

The respiratory and digestive systems start to work independently.  


Foetal Viability (premature survival)   


At around 5.5 - 6.5 months after conception, the foetus reaches the age of viability, at this age a foetus has some chance of surviving outside of the womb (uterus) if it were to be born prematurely. The chances of a premature baby surviving increases significantly with each additional week that it remains in the mother’s womb (uterus).  


Adverse Factors Affecting Foetal Development:  


The womb provides some protection to the foetus; however, it does not act as a complete barrier and therefore many harmful agents can cross the placenta and impact foetal growth and development. 


Poor nutrition  

Alcohol, smoking and recreational drugs 

Certain prescription or over-the-counter drugs  

Radiation (x-rays etc.)  

Heavy metals (lead, mercury, cadmium)  

Toxins (solvents, PBCs, dioxins)   

Infections (AIDS, German measles, syphilis, cholera, smallpox, mumps, or severe flu).   


Foetal Alcohol Syndrome:   


Mothers who drink heavily during pregnancy may give birth to babies with foetal alcohol syndrome and is incurable. Clinical characteristics include: small head size, heart defects, irritability, hyperactivity, mental retardation, or slowed motor development (referring to bones, muscles and movement).  


Pregnancy trimesters:  


Pregnancy takes up to 39 weeks and is divided into 3 trimesters, each 13 weeks in length: 

1st trimester (13 weeks) = embryonic stage 

2nd trimester (13 weeks) = early foetal stage  

3rd trimester (13 weeks) = late foetal stage 


The importance of weight gain and an infant's birth weight? 


After the first trimester, weight gain increases to between 350-400g per week and the total weight gain in pregnancy is between 11-15kg. This weight gain is made up of: the foetus, placenta, blood volume, adipose tissue (fat), protein, increase in uterus size and breasts as well as water retention.  


The birth weight of an infant is the best indicator of its overall nutritional status. A birth weight of above or below a normal range of between 2.5 - 4.2 kgs - increases the risk of stillbirth, disease in the first year of life and the development of chronic diseases later in life.  


Common (normal) symptoms during pregnancy:  


Morning sickness (nausea + vomiting) 

Heart burn  

Changes in bowel habits  

Increased urination  



Shortness of breath  

Rapid heartbeat/ palpitations  




Unusual cravings can develop during pregnancy, such as cravings for ice, freezer frost, laundry starch, corn starch, clay, dirt, dust, chalk, plaster and charcoal. Certain pica cravings may indicate nutrient deficiencies, such as iron and calcium. 


The Baby Blues:  


Fluctuations in female sex hormones – influence brain neurotransmitters – directly impacting mood, sleep and energy:  


Serotonin (mood, appetite and sleep)  

Adrenaline/ noradrenaline (energy) 

Opioids/ Endorphins (pain, reward and addiction)  

GABA (relaxation and sleep) 


After childbirth, the level of hormones; oestrogen and progesterone in a woman’s body quickly drop. This leads to chemical changes in her brain that may trigger conditions known as “postpartum affective instability” (mild) or “postpartum depression” (severe). These conditions include symptoms such as anxiety, sadness and fatigue. Constant sleep deprivation (due to child care) can lead to physical discomfort and exhaustion, further intensifying pre-existing symptoms.   


The “baby blues” (postpartum affective instability), affects up to 80% of mothers and includes feelings that are mild, lasts for 1-2 weeks and goes away on its own.  


With postpartum depression, feelings of sadness and anxiety can be extreme and may interfere with a woman’s ability to care for herself and her family. Postpartum depression affects up to 15% of mothers and commonly begins within the first month after childbirth. Unlike the baby blues, this condition may not go away on its own and therefore may need to be managed using conventional and alternative interventions.