Pregnancy Screening / Reproductive Screening
From WikiGenetics
[edit] Prenatal Diagnosis
Prenatal diagnosis refers to testing performed during a pregnancy. Prenatal diagnosis is helpful for determining the outcome of the pregnancy, planning for possible complications during delivery, planning for problems that may occur in the newborn, deciding whether to continue the pregnancy, and finding conditions that may affect future pregnancies.
A common reason for prenatal diagnosis is the mother’s age. According to professional guidelines, prenatal diagnosis should be offered to women who will be over the age of 35 years at the time of delivery because of an increased risk of having a child with a chromosome abnormality such as Down syndrome. Children with Down syndrome have a distinct facial appearance and mental retardation; however, the severity of the disease can vary greatly from child to child. The disease is caused by an extra copy of chromosome 21 (trisomy 21).
Other possible reasons for prenatal diagnosis include: a previous child with a genetic condition, a fetus known to be at risk for a genetic condition because both parents are mutation carriers, a family history of a genetic condition, a positive prenatal screening test (triple/quadruple/first trimester screen), or abnormal ultrasound findings.
Several types of prenatal diagnosis are available depending how far along the pregnancy is and what type of disorder is being tested. Chorionic villus sampling (CVS) and amniocentesis are two common procedures used to obtain a sample for further testing.
Amniocentesis and Chorionic Villus Sampling are both invasive procedures that carry a risk of miscarriage (less than 0.5% for amniocentesis and about 1% for CVS). Amniocentesis involves removing a sample of amniotic fluid that surrounds the fetus by inserting a syringe through the abdomen. The technique is generally performed at 15 to 20 weeks gestation. In CVS, the fetal cells are removed from an area around the fetus known as the chorion with a syringe inserted through the cervix or abdomen. CVS can be performed as early as nine week’s gestation, but based on safety data, it is typically performed at 10 to 13 weeks’ gestation. This allows the results to be available at an earlier stage of pregnancy. Both amniocentesis and CVS samples contain fetal cells that can be grown in the laboratory for genetic testing.
[edit] References
Genetic Alliance. 2007. Understanding Genetics: A Guide for Patients and Health Care Professionals. http://www.geneticalliance.org/ws_display.asp?filter=understanding.genetics.download
