The Australian Bureau of Statistics has detailed demographical information about the Australian population.
Over the last 30 years there has been a decrease in teenage women having children, with most women now have children when they are older (28-31 age), but older women (40+) are also decreasing. The text excerpt below in "Births" is an analysis of birth trends this century in Australia from Australia Now (ABS).
A separate body, The Australian Institute of Health and Welfare National Perinatal Statistics Unit, also keeps accurate Australia-wide statistics on Major Congenital Malformations in Australia.
In 1903, when the crude birth rate was lower than it had ever been before, the Royal Commission On the Decline in the Birth-rate and On the Mortality of Infants in New South Wales was appointed. It reported in 1904 and concluded that '...the cause or causes of the Decline of the Birth-rate must be a force or forces over which the people themselves have control...'. In other words, couples were limiting the size of their families.
At the turn of the century there were 117 births per 1,000 women of child bearing age (15-44 years). This approximates a total fertility rate of 3.5 babies per woman. By 1924 the total fertility rate was 3.0 and falling.
In 1934, in the middle of the Great Depression, the total fertility rate fell to 2.1 babies per woman. It then increased during the second half of the Depression, as women who had deferred childbearing in the early years of the Depression began to have children. Fertility increased through World War II and the 1950s, and peaked in 1961 when the total fertility rate reached 3.6 babies per woman. This period of high fertility is known as the baby boom (see graph 5.28).
After the 1961 peak, the total fertility rate fell rapidly, to 2.9 babies per woman by 1966. This fall can be attributed to changing social attitudes, in particular a change in people's perception of desired family size, facilitated by the contraceptive pill becoming available.
During the 1970s the total fertility rate dropped again, falling to below replacement level in 1976 where it has remained since. This fall was more marked than the fall in the early 1960s and has been linked to the increasing participation of women in the labour force, coupled with changing attitudes to family size, standard of living and lifestyle choices.
Women are starting childbearing later in life, and are having fewer children. In 1966, peak fertility was among 25 year old women, with 21% having babies. By 1996, peak fertility was among 29 year old women, but only 13% had babies. Primarily because fewer women are having large families, the proportion of all women having babies after they turn 40 has fallen (see graph 5.29).
In the last 30 years, there has been a fall in the proportion of births to teenage mothers, from 11.3% of all births in 1966 to 4.9% in 1996. The number of babies born to mothers aged 40 years or over has also fallen, from 2.6% in 1966 to 2.1% in 1996.
Excerpt from Australia Now (ABS)
The full Report on Maternal Deaths in Australia 1991-93 is available from the NHMRC as a PDF Document.
In the 1991-93 triennium, there were 84 maternal deaths in Australia.
Direct maternal deaths (those resulting from complications of pregnancy) accounted for 27 deaths.
Indirect maternal deaths (from pre-existing diseases aggravated by pregnancy) accounted for 21 deaths.
The other 36 deaths were incidental maternal deaths (occurring in pregnancy but where the pregnancy was unlikely to have contributed significantly to the death e.g. road accidents, malignancies and suicides). This, the largest group of deaths, is not included by the World Health Organization definition, or in maternal mortality statistics reported from most other countries. An avoidable factor was considered to be present in 12 of the maternal deaths.
The overall maternal mortality rate was 10.9 maternal deaths per 100,000 confinements. This result is the lowest on record and is creditable in comparison with those of all other developed countries.
These developmental abnormalities usually involve only small DNA mutations affecting individual or a few genes, two exceptions are the major chromosomal abnormalities usualy trisomy; trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome) (also trisomy 9, 13, 15). Note that the occurance of chromosomal abnormalities also increases with increasing maternal age.
There are many pamphlets providing information about prenatal diagnosis (see NSW State Health Publication Checking your baby's health before birth).
A better understanding of abnormal development can also be gained from looking at normal birth statistics
Relate to lifestyle, environment and nutrition. Some examples of this form of abnormality are the impact of excess alcohol on neural development (Fetal alcohol syndrome), viral infection (rubella) at a critical stage of development, inadequate dietry folate intake (neural tube defects), effects of prescription drugs (Thalidomide- limb development) and even maternal endocrine function (thyroid development).
In addition to these obvious maternally-derived abnormalities, there is growing evidence that the interuterine environment has a strong influence on later postnatal health. This theory is based on the early statistical analysis of disease/longevity in babies with low birth weights in England by Barker, and has been called the "Barker Hypothesis". (More? Barker Hypothesis)
Each section of the notes covering early development and specific systems contain references to specific abnormalities (on Page 2 of each notes section). The best source for Australian statistical data is the Australian Institute of Health and Welfare National Perinatal Statistics Unit, UNSW which publishes "Congenital Malformations Australia" every 2 years. Be aware that some congenital abnormalities, by their nature, affect multiple systems. In the USA, the Center for Disease Control (CDC) keeps and publishes relevant statistical information. A very difficult issue in abnormal development are the many different Ethical implications.
This current page is a link to Normal and Abnormal Development and Population Data.
You should look at normal development. Development Notes
Alternatively, go on to look at Systematic Development of organs and tissues.
For those wanting to see dynamic processes of development (and have a reasonably quick connection) then the Movies pages are good for watching changes occur.
The study of human development has relied extensively on studying the process in other model animals. For those wanting to see the process of development in other species then the other embryos pages are a good start.
Please email Dr Mark Hill if you wish to make a comment about this current project.