Negative Influences on the Developing Fetus

Negative Influences on the Developing Fetus

The purpose of this posting is to discuss the maternal / paternal, environmental, and teratogenic factors that have a negative influence on the developing fetus. This information will be related to how it concerns the practice of mental health counseling.

Maternal and paternal factors both affect the developing fetus. According to the reading in Broderick and Blewitt 23 of the 46 chromosomes were contributed by the father so his part can not be down played. With personal experience under the belt of having to boys. It can honestly be stated that during labor and delivery, kind thoughts about their father's role, especially during the painful part, did enter into the equation. Hereditary diseases, according to Broderick and Blewitt, are passed on from parents to children, and the blame could either be a function of normal hereditary processes, or because something went wrong during the production of the ova or the sperm. Disorders can be influenced by recessive, defective alleles, dominant, defective alleles, disorders of polygenic origin, chromosomal abnormalities, and sex-linked disorders.

According to Broderick and Blewitt "many hereditary disorders are caused by recessive. defective alleles, and it is estimated that most people are carriers of three to five such alleles." Most of the illnesses are said to be rare because the individual has to be unlucky enough to have both parents be carriers of the same defective allele, and then to be the one in four (on average) that gets the recessive alleles from both the mother and the father (Broderick & Blewitt, 2006). The disorders that have been traced to recessive gene alleles are; Cystic fibrosis, PKU, Sickle-cell anemia, Tay-Sachs disease, Thalassemia, Hemophilia, and Duchenne's' muscular dystrophy. The last two disorders mentioned are X linked and are expressed primarily or exclusively in males (Table 2.3, p.41). In order to be an good genetic counselor it seems that not only do mom and dad play a large part, but there is also a huge connection to the generations that came before them.

Disorders that are influenced by dominant, defective alleles are related to one defective gene. There are no carriers of such disorders. Anyone who has a defective gene will have the problem, due to the fact that the dominant gene allele is always expressed in the phenotype (Broderick & Blewitt, 2006). If the illness causes the early death of the individual then the illness will die with the victim and not be passed on to the next generation. If the alleles pop up in a future generation it is said to be the product of spontaneous mutation or because of an environmental influence. If the victim does not die during childhood there is always a chance that the dominant, defective allele can be passed from one generation to the next. If one parent has the disease there is a 50% chance that the fetus will inherit this gene from the parent who carries it.

Disorders of a polygenic origin are said to be related to multiple pairs of genes and the combination of defective alleles at several chromosomal sites (Broderick & Blewitt, 2006). The diseases that have been indicated to be of a polygenic nature include; most forms of muscular dystrophy, diabetes, clubfoot, some forms of Alzheimer's disease, and multiple sclerosis (Broderick & Blewitt, 2006). It was stated that genetic effects on behavioral traits are usually polygenic in nature. "This appears to be true for many mental illnesses and behavioral disorders as well, such as alcoholism, criminality, schizophrenia, and clinical depression" (e.g., Charney, Nestler, & Bunnet, 1999; DeAngelis, 1997; Heath et. al., 1997; Plomin, Owen, & McGuffin, 1994).

Disorders caused by chromosomal abnormalities are related to a zygote containing too many, or too few chromosomes. Most zygotes with chromosomal abnormalities are not viable and do not survive. If they do survive, the fetus will usually have several physical or mental problems. Down syndrome, also referred to as Trisomy 21, is related to a chromosomal abnormality. An important point to consider with Down syndrome, is the increased risk related to the mothers parental age at conception. This risk does not seem to hold true with fathers who are older (Merewood, 1991).

Sex-linked disorders are related to X-linked recessive disorders like hemophilia, baldness, color blindness, night blindness and Duchenne's muscular dystrophy (Broderick & Blewitt, 2006). Males are more likely to inherit these disorders than females. This is due to the fact that if the male inherits the defective gene allele on the X chromosome, the Y chromosome does not have a matching gene to cancel out the recessive, defective gene allele inherited from the mother. Ok, we are the culprits in this case, since we are the carriers and our victims are male.

The environmental influences on prenatal development include teratogens, nutrition and stress. To start with teratogens there is a good fetal development figure located on page 37 of the text. Depending on what stage of embryonic development, the type and amount of teratogen, and the common site of action of the teratogen, many problems can occur during fetal development. From the figure, during the 3rd through

the 16th week of pregnancy, the embryo's period of greatest sensitivity to teratogens, many parts of the developing fetus can be affected. It is indicated that the developing sites affected by teratogens include the central nervous system, the heart, eyes, limbs, ears, teeth, palate, brain, and external genitalia. The central nervous system, eyes, teeth, and external genitalia continue to be affected, but to a lesser degree, until the fetus is born. The problems indicated could be as great as major morphological abnormalities, to functional defects and minor morphological abnormalities. The how's, why's, amounts and affects of most teratogens are still being studied and researched. The best bet is to steer clear of any teratogen that is known to cause damage, look into where you live, and conduct some research into the potential environmental problems in the area. Since the potential for harm is not yet predicted with accuracy, the more we know and stay away from what we can, the better off the developing fetus will be.

The damage done, as stated before, coincides with the stage of development the fetus is in when the mother is exposed to the teratogen. The other consideration is the indication that the mother's and baby's genes also play a role in sensitivity, and or the resistance to teratogens. This is the reason that researcher's and scientists