Prenatal Environmental Influences:

In this blog I will discuss the many environmental factors which influence the growth and development of fetal tissues. Though we only require one pathology which may influence our tissue, i've gone into detail of all the important ones which influence fetal tissue because it is extremely interesting to see the different things which could of affected our own individual growth. Feel free to read as much as you choose, though everything is extremely interesting.

Teratogens:

The term teratogen refers to any environmental agent that causes damage during the prenatal period. It come from the Greek word teras, meaning "malformation" or "monstrosity." This label was selected because scientists first learned about harmful prenatal influences from babies who had been profoundly damaged (Berk, 2003).

(1) Prescription and Nonprescription Drugs:

In the early 1960s, the world learned a tragic lesson about drugs and prenatal development. At that time, a sedative called thalidomide was prescribed in Canada, Europe, and South America to help with symptoms associated with morning sickness. When taken by mothers between the fourth and sixth week after conception, thalidomide produced gross deformities of the embryo's developing arms and legs, less frequently, damage to the ears, heart, kidneys, and gentials. Also children exposed to thalidomide grew older, many scored below average in intelligence (Berk, 2003).

Another medication, a synthetic hormone called diethylstilbestrol (DES), was widely prescribed between 1941 and 1971 to prevent miscarriages. As daughters of these mothers reached adolescence and young adulthood, they showed unusally high rates of cancer of the vagina and malformations of the uterus (Berk, 2003).

Any drug taken by the mother that has a molecule small enough to penetrate the placental barrier can enter the embryonic or fetal bloodstream. Despite the lesson of thalidomide, many pregnant women continue to take over-the-counter drugs, such as aspirin, without consulting their doctors which may lead to low birth weight of the baby (Berk, 2003).

(2) Illegal Drugs:

The use of highly addictive mood-altering drugs, such as cocaine and heroin has become widespread. Babies born to users of cocaine, heroin, or methadone are at risk for a wide variety of problems, including prematurity, low birth weight, physical defects, breathing difficulties, and death around the time of birth. In addition, these infants arrive drug addicted. They are often feverish and irritable and have trouble sleeping (Berk, 2003).

Throughout the first year, heroin and methadone exposed infants are less attentive to the environment, and their motor development is slow. After infancy, some children get better, whereas others remain jittery and inattentive. The kind of parenting these youngsters receive may explain why problems last for some but not for others (Cosden, Peerson, & Elliott, 1997).

Growing evidence on cocaine suggests that many prenatally exposed babies have lasting difficulties. Cocaine constricts the blood vessels, causing oxygen delivered to the developing organism to fall dramatically for 15 minutes following a high dose. It also alters the production and functioning of neurons and the chemical balance in the fetus's brain. These effects may contribute to a specific set of cocaine-linked physical defects, including eye, bone, genital, urinary tract, kidney, and heart deformities, as well as brain hemorrhages and seizures (Berk, 2003).

(3) Tobacco:

The most well-known effect of smoking during pregnancy is low birth weight. But the likelihood of other serious consequences, such as miscarriage, prematurity, impaired heart rate and breathing during sleep, infant death, and cancer later in childhool, is also increased. The more cigarettes a mother smokes, the greater the chances that her baby will be affected. If a pregnant woman stops smoking at any time, even during the last trimester, she reduces the likelihood that her infant will be born underweight and suffer from future problems (Berk, 2003).

(4) Alcohol:

Fetal Alcohol Syndrome (FAS) is the name for a constellation of symptoms that include mental retardation, overactivity, and impairments in motor coordination, attention, memory, language, planning, and problem solving. Accompanying physical symptoms include slow physical growth and a particular pattern of facial abnormalities: widely spaced eyes; short eyelid openings; a small, upturned nose; a thin upper lip; and a small head, indicating that the brain has not developed fully. Other defects may include the eyes, ears, nose, throat, heart, genitals, urinary tract, or immune system (Berk, 2003).

In all babies with FAS, the mother drank heavily through most or all of her pregnancy. Sometimes children display only osme of the physical abnormalities associated with FAS. In these cases, the child is said to suffer from fetal alcohol effects (FAE). Usually, their mothers drank alcohol in smaller quantities or less often. The particular defects of FAE children vary with timing and length of alcohol exposure during pregnancy (Berk, 2003).

(5) Radiation:

When mothers are exposed to radiation during pregnancy, harm can come to the embryo or fetus. Defects due to radiation were tragically apparent to the children born to pregnant Japanese women who survived the atomic bombing of Hiroshima and Nagasaki during World War 2. Similar abnormalities surfaced in the 9 months following the 1986 Chernobyl, Ukraine, nuclear power plant accident. After each disaster, the incidence of miscarriage, small head size (indicating an undeveloped brain), physical deformities, and slow physical growth rose dramatically (Berk, 2003).

(6) Environmental Pollution:

An astounding number of potentially dangerous chemicals are released into the environment in industrialized nations. Over 100 000 are in common use, and many new ones are introduced each year.

Mercury: is an established teratogen. In the 1950s, an industrial plant released waste containing high levels of mercury into a bay providing food and water for the town of Minimata, Japan. Many children born at the time were mentally retarded and showed other serious symptoms, including abnormal speech, difficulty in chewing and swallowing, and uncoordinated movements. Autopsies of those who died revealed widespread brain damage (Dietrich, 1999).

Lead: is another teratogen. It is present in old paint and in certain industrial materials. High levels of lead exposure are consistently related to prematurity, low birth weight, brain damage, and a wide variety of physical defects (Berk, 2003).

Polychlorinated biphenyls (PCBs): were used to insulate electrical equipment for many years, until research showed that they found their way into waterways and entered the food supply. Prenatal exposure to very high levels of PCBs in rice oil resulted in low birth weight, discoloured skin, deformities of the gums and nails, brain-wave abnormalities, and delayed cognitive development (Berk, 2003).

(7) Maternal Disease:

Five percent of women catch an infectious disease while pregnant. Most of the illnesses, such as the common cold, seem to have no impact on the embryo or fetus. However, a few diseases can cause extensive damage.

Viruses: Rubella ~ is a well known teratogen. In the mid-1960s, a worldwide epidemic of rubella led to the birth of many thousands of babies with serious defects. The greatest damage occurs when rubella strikes during the embryonic period. More than 50 percent of infants whose mothers become ill during that time show heart defects; eye cataracts; deafness; gential, urinary, and intestinal abnormalities; and mental retardation. Infection during the fetal period is less harmful, but low birth weight, hearing loss, and bone defects may still occur (Berk, 2003).
The Human Immunodeficiency Virus (HIV) ~ which leads to acquired immune deficiency syndrome (AIDS), a disease that destroys the immune system, has infected increasing numbers of women over the past decade. When AIDS victims become pregnant, about 20 to 30 percent of the time they pass the deadly virus to the developing organism. AIDS progresses rapidly in infants. By 6 months, weight loss, diarrhea, and repeated respiratory illnesses are common. The virus also causes brain damage. Most prenatal AIDS babies survive only 5 to 8 months after the appearance of symptoms (Berk, 2003).

Bacterial and Parasitic Diseases: Among the most common is toxoplasmosis, cuased by a parasite found in many animals. Pregnant women may become infected from eating raw or undercooked meat or from contact with the feces of infected cats. About 40 precent of women who have the disease transmit it to the developing organism. If it strikes during the first trimester, it is likely to cause eye and brain damage. Later infection is linked to mild visual and cognitive impairments (Berk, 2003).