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Posted on March 8th, 2013, by

Prenatal Development and Critical Periods
Prenatal Development is a complex process during which an embryo is gestated starting from fertilization to birth. Prenatal development includes the following stages:
the germinal stage (the sperm and egg are united in one of the tubes, the egg is fertilized and moves to uterus, after cell division the cells are developed in blastocyst which moves to uterus and fixed to uterine wall);
the embryonic stage which include implantation and cell differentiation into different body systems;
the fetal stage during which the embryo passes to the stage of fetus. (Cherry)
Critical periods are such periods of pregnancy when there is a high risk of termination of pregnancy. They include the following ones:
I trimester: 2-3 week; 8-12 weeks;
II trimester: 18-22 weeks;
III trimester: 28-32 weeks. (Altshuler et al., 2003, p.3)
Definition of Teratogen
Teratogen is an agent which can interfere with the normal fetus development and cause loss of the pregnancy or some problems with health of the fetus or some complications in the process of pregnancy.
Six Teratogens and their Effects on Prenatal Development
It is known that the following teratogens are very dangerous for the successful development of pregnancy:

Environmental teratogens which include radiation, fumes, and influence of other chemical substances which were can cause a threat to the fetus as well as mechanical forces such as traumas and so on.
Infections. Different infections can cause the pregnancy termination or health disorders of the unborn child.
Drugs and medications. Such drugs as tetracycline, phenytoin, retinoic acid, tranquilizer thalidomide and a great deal of other teratogens can cause mental retardation and other health disorders. (Chung, 2009, p.20)
Nicotine. This teratogen has an enormous effect on the growth of the fetus and on the mental development of the unborn child.
genetic teratogens which include chromosomal abnormalities and disorders and defects of the single gene. They can cause Dawn Syndrome and heart diseases, growth and mental retardation.
maternal medical conditions. For example, there is a high risk to have a heart disease if the mother of the unborn child is diabetic. (Chung, 2009, p.23)
Fetal Alcohol Syndrome
Fetal Alcohol Syndrome or FAS stands for the mental and physical defects which are developed in the fetus if the mother takes alcohol drinks during her pregnancy. (Sayford-Wilson, 2010, para.1)
Cognitive and Physical Effects of Alcohol
It is known that alcoholic mothers have a high risk of different disorders of their infant. The cognitive and physical effects of alcohol include the following ones:
low birth weight;
different facial abnormalities such as small head, small eyes openings and so on;
serious organ malfunctions;
loss of coordination;
various neurological problems such as loss of some motor skills, hearing loss, epilepsy, clumsiness;
poor memory;
mental retardation;
congenital heart diseases;
non-development of some organs or hypoplasia;
invariable behavior;
great problems with learning, intellectual disability.(Malbin, 2002, p.12)
The first trimester is considered to be the most critical period for alcohol as the development of embryo is susceptive to toxic exposures to a great extent. (Malbin, 2002, p.16)

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