Normal prenatal development occurs in 95 to 98 percent of all pregnancies. Identify two genetic or chromosomal abnormalities and two teratogens associated with birth defects in the remaining 2 to 5 percent of pregnancies. Describe the nature of their effects on development.

Question

What will be an ideal response?

Answer 1

Students' examples may vary.

The answer should include the following information:

Some of the genetic or chromosomal abnormalities are listed below.

Phenylketonuria (PKU): A child born with the inherited disease phenylketonuria cannot produce an enzyme that is required for normal development. This deficiency results in an accumulation of poisons that eventually cause profound intellectual disability.

Sickle-cell anemia: About 10 percent of the African American population has the possibility of passing on sickle-cell anemia, a disease that gets its name from the abnormally shaped red blood cells it causes. Children with the disorder may have episodes of pain, yellowish eyes, stunted growth, and vision problems.

Tay-Sachs disease: Children born with Tay-Sachs disease, a disorder most often found in Jews of Eastern European ancestry, usually die by age 3 or 4 because of the body's inability to break down fat.

Down syndrome: Down syndrome, one of the causes of severe mental disabilities, occurs when the zygote receives an extra chromosome at the moment of conception. Down syndrome is often related to the mother's age; mothers over 35 and younger than 18 stand a higher risk than other women of having a child with the syndrome.

Some of the teratogens associated with birth defects are as follows:

Mother's nutrition: What a mother eats during her pregnancy can have important implications for the health of her baby. Seriously undernourished mothers cannot provide adequate nutrition to a growing fetus, and they are likely to give birth to underweight babies. Poorly nourished babies are also more susceptible to disease.

Mother's illness: Several diseases can have devastating consequences for a developing fetus if they are contracted during the early part of a pregnancy. For example, rubella (German measles), syphilis, diabetes, and high blood pressure may each produce a permanent effect on the fetus.

Mother's use of drugs: Mothers who take illegal physically addictive drugs such as cocaine run the risk of giving birth to babies who are similarly addicted. Their newborns suffer painful withdrawal symptoms and sometimes show permanent physical and mental impairment.

Alcohol: Alcohol is extremely dangerous to fetal development. For example, as many as 1.5 out of every 1,000 infants is born with fetal alcohol syndrome disorder (FASD), a condition resulting in below-average intelligence, growth delays, and facial deformities. Even mothers who use small amounts of alcohol during pregnancy place their child at risk.

Nicotine use: Pregnant mothers who smoke put their children at considerable risk. Smoking while pregnant can lead to miscarriage and infant death. For children who do survive, the negative consequences of mother's tobacco use can last a lifetime.