Final answer:
Screening for tube defects and chromosomal abnormalities through a quad screen is done between the 15th and 20th weeks of pregnancy as a maternal blood test. Age is a risk factor for chromosomal abnormalities. Genetic counselors play a key role in interpreting risks and screening results.
Step-by-step explanation:
Screening for tube defects and chromosomal abnormalities, such as Down syndrome, is usually conducted through what is known as the quad screen. Screening is typically done between the 15th and 20th weeks of pregnancy. It involves a maternal blood test that measures levels of four substances, which can provide information about the likelihood of certain birth defects and chromosomal conditions, including neural tube defects and chromosomal disorders.
With increasing age, women are at an increased risk of having a baby with a chromosomal abnormality. This is because the likelihood of errors occurring during cell division rises as women age. As such, age is considered a significant risk factor when assessing the likelihood of chromosomal abnormalities.
Consultation with a genetic counselor is advised, especially for those who are of advanced age, have a family history of genetic disorders, or have received a high-risk result from screening. A genetic counselor can help couples understand screening results, implications of various genetic and chromosomal disorders, and assist in making informed decisions on further testing, such as amniocentesis or chorionic villus sampling (CVS).