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Ordinarily, miscarriages due to abnormality of the uterus or some genetic disorder are possible between conception and about 13 weeks. Women who are concerned about the possibility of genetic abnormalities can undergo amniocentesis, a procedure in which cells in the amniotic fluid are examined for chromosomal damage. Another prenatal test, called chorionic villi sampling (CVS), analyzes a sample of embryonic tissue for defects. This procedure can be safely used during the first trimester of pregnancy (Kolata, 1983). A more common testing procedure is ultrasound, in which extremely high-pitched sound waves are bounced off the embryo or fetus to produce a picture. Ultrasound can help determine the position of the fetus, identify structures, and monitor heartbeat when a medical problem exists.
The first three months of pregnancy, called the first trimester, are considered a critical period because during this period external stimuli can affect the pregnancy drastically. The mother must be especially careful not to contract contagious diseases such as German measles, take drugs other than those prescribed by her doctor, or have excessive X-rays taken, for any of these outside stimuli could disrupt normal development. For instance, recent research has shown that cigarette smoking during pregnancy can result in premature birth of the baby. It may be that nicotine and other chemicals can penetrate the placenta to affect the fetus. Infants born to women who drink alcohol excessively during pregnancy may have fetal alcohol syndrome (FAS). FAS is a leading cause of mental retardation. FAS infants are usually underweight at birth and have physical and cognitive problems throughout life (Steinhausen & colleagues, 1993). For example, they may exhibit speech and hearing problems, poor attention span, learning problems, and hyperactivity (Short & Hess, 1995). Especially prevalent in FAS individuals is hearing loss and speech disorders. A recent study found nearly all of the patients tested exhibited significant problems in this area (Church & colleagues, 1997). Recent research also indicates that FAS is more prevalent in low SES mothers (Abel, 1995). Infants born to mothers who are users of heroin or cocaine may suffer from inhibited growth and have withdrawal symptoms. Similarly, children born to mothers who have taken the antibiotic drug streptomycin may be deaf. Even high doses of certain vitamins, such as A and D, can cause problems in offspring. The AIDS virus has been found to infect unborn children (Diamond & colleagues, 1990). |
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