Research Paper on "Pre-Natal Development"

Research Paper 5 pages (1901 words) Sources: 6

[EXCERPT] . . . .

Prenatal development involves not only the physiologic processes which occur to produce life, it also requires an understanding of the various influences that shape the developing life and the consequences those influences have the potential to bear. The issue of nature vs. nurture is brought to bear in prenatal development. With a focus on the inherent 'tabula rasa' character of the nature side, as influenced by the outside environmental factors that can impact the fetus, it becomes clear that prenatal development is a stochastic process. Items that must be considered are the behaviors of the mother, the environment in which she lives, prenatal care, and other external factors like the food, air, and water that the mother intakes. Prenatal development is a process that is begun by nature, yet influenced by nurture.

Introduction

Pregnancy is a time of incredible growth, for both woman and the developing baby. Most of the time, the natural process of pregnancy is not thought of in any depth on the part of the woman, in terms of cell division, organ formation, and the other intricate and delicate happenings that produce life. This paper will provide an overview of the stages of prenatal development, the periods and stages, and offer a discourse of the issue of nature vs. nurture. Within the nature/nature examination, a proof will be extended on the role of epigenetics as influencing prenatal development.

Stages of Development

Pregnancy is divided into three main time periods, or stages, with differing developmental processes occurring within each stage. The first stage is known as the first trimester which begins with fertilization, and ends at the twelfth week. The second stage is the second trimester, lasting from the weeks thirteen through twenty-seven. The third trimester (stage) last from week twenty-eight to week forty-two (Shibley Hyde & DeLamater, 2007).

The germinal stage begins with fertilization; the process of cell division takes off at an astounding rate. The ovum and the sperm combine, contributing genetic material from their respective nucleus, and the process begins.

This is referred to as the embryonic period, which begins at conception, and ends at the tenth week of development in the gestational period. The fertilized egg, or zygote, travels slowly down the Fallopian tube. This process usually takes 3-5 days. As it journeys, it is undergoing cell division, and forms a ball of cells. At this time this ball of cells is known as the morula, and a small cleft forms between the cells. At this stage, the conceptus is officially known as a blastocyst (Schultz, 2005).

The blastocyst enters the uterus at approximately the fifth day following conception (fertilization). A glycoprotein shell forms, which enables the blastocyst to adhere to the uterine wall. The significance of the glycoprotein shell is that the cells which develop into the placenta thus need to be able to come into contact with the uterine wall in order to develop; hence, the shell enables those precursor placental cells to contact the wall of the uterus (Ohlsson, Larsson, Nilsson, Wahlstrom, & Sundstrom, 1989). The fertilized egg travels down the fallopian tube to the uterus, where it implants in the uterine wall. Officially, at this point, implantation has occurred, and the embryonic stage has begun.

During the embryonic stage, a different developmental process takes place. Here, the inner cells of the blastocyst develop into the embryo while the outer cells develop into the placenta and membranes. Growth is happening quite rapidly, and the embryo is starting to take shape. This is called the process of differentiation, as the embryonic process produces different cell types. This process leads to different growth variables where cells develop into various body phenomena, such as organs, nerve cells, and blood cells (Red Horse & al., 2004).

If an abnormality exists in the embryo or placenta, or if there is an error of development in some fashion, a spontaneous abortion or miscarriage may happen. Needless to say, during this time of critical development, the developing embryo is the most susceptible to environmental toxins (Shibley Hyde & DeLamater, 2007). The term 'environmental' is used here to connote things that are not inherent in the embryo cell body; rather, it means things outside of the embryonic mass.

Nature vs. Nurture

The nature vs. nurture issue, in terms of prenatal development, asks us whether the inherent biological factors that produce life (i.e. genetics) are more important than the outside, external factors that frame the setting in which life occurs (i.e. anything external to the fetus) (Ridley, 2003). This is the kernel of the difference between the two issues; indeed, they are opposing sides of the same coin.

Is the inherited genetic material impacted by one's environment? The discourse surrounding the argument is such: the nature principle states that people are born with genetic engraving; that is, their personalities are inherent in their genetic code as a starting point. The nurture principle explains that while people are born with genetic predispositions for certain personality and physical traits, the actual outcome depends upon the environmental inputs they receive. In no place is this more critical, than during the prenatal stage (Belsky & Pluess, 2009).

The Role of the Mother's Behavior

During the 1950's in the United States, it was not uncommon for a pregnant woman to have an alcoholic beverage, or smoke a cigarette, without censure. The womb was viewed as the closed-off, protected haven in which the baby was developing, secure from the insults of the outside world (Harley & Eskenazi, 2006).

However, as science has shown us, both cigarette use and alcohol use can have significant teratogenic effects on the developing fetus. Cigarettes contain substances, like nicotine, which not only affect the mother, they also affect the fetus. The placenta is not a barrier; it is a conduit between the mother's body and the developing baby's body. For example, nicotinic effects on the mother include vasoconstriction, which means that blood vessels constrict. Obviously, this is not good for the baby. Less blood flow means less oxygen, less oxygen leads to neurobiological consequences. Likewise, alcohol consumption by the mother displaces oxygen in her blood stream. A lack of oxygen in her bloodstream (in addition to the poisonous effects of alcohol) impacts the baby, sometimes quite severely. Fetal Alcohol Syndrome is one leading malady arising from substance abuse of alcohol by the mother during pregnancy (Pietrantoni & Knuppel, 1991). The most critical period of something environmental having the potential to adversely impact the course of prenatal development, is the embryonic period or first trimester.

The Role of Epigenetics

The field of epigenetics is a fascinating field of inquiry. Epigenetics refers to the changes in the expression of the phenotype of the inherited genes. A simple example is the case of the Agouti Mice. Here, the scientists demonstrated that by supplementing the pregnant mother with metafolin and other vitamins, that they could manipulate the coat color of the offspring (DC, D, & RL., 2007). This is clearly an example of how nurture (the intakes) influences nature (the tabula rasa).

For a mother who is consuming alcohol to excess, the effects are more clear-cut. Science has shown us that alcohol is a toxic to the fetus. Mental retardation, seizures, and other severe cognitive deficits can occur. Another example that is less clear cut (meaning, science still cannot explain why this works) is that mothers are encouraged to take prenatal supplements which contain abnormally high levels of folic acid. The rationale is that since this policy was adopted by doctors, the rates of spina bifida have decreased. Indeed, since the Agouti mice and human mothers alike are taking folic acid (metafolin), one wonders at the effects the substance is having on the rest of the human genome (Y, L, G, L, & MJ., 2010).

To elaborate, folic acid has been shown to influence the phenotypic expression of certain traits in mice studies. Folic acid has also been shown to influence the rates of spina bifida in human mothers. Folic acid, in general, causes a genetic process that affects the very expression of genes; it affects the chromatin structure of genes. To illustrate, a chromosome is made up of a protein core, around which the DNA wraps itself. There are other genes that are responsible for tightening and loosening the bands of DNA. When the DNA is 'tightly wrapped' the genes do not express. When the DNA is 'loosely wrapped', the genes express their product (which is mRNA, the messengers that tell the cell what proteins to produce and how, etc.). Folic acid causes a modification of the chromatin structure, such that the genes wrapped around it will express their product differently than they would without the folic acid. Whether this is a good thing or a bad thing, remains the realm of scientific study. It does seem, prima facie, a dangerous game to play to take a substance without fully knowing the effects (Szyf, 2009).

Conclusion

Prenatal development progresses through many stages, from germination in the first trimester, to birth in the third trimester.… READ MORE

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