文档介绍：18 疾病的产前诊断 Prenatal Diagnosis of Disease
ic diseases and congenital malformations occur in approximately 2 to 5 % of all live births, account for up to 30% of paediatric admissions to hospital, and are an important cause of death under the age of 15 years.
Furthermore, the psychological stress on families with children with serious ic disorders is incalculable. Until gene therapy es a practical reality, the only option available for the control of ic disease is prenatal diagnosis.
1. Indications for prenatal diagnosis
The use of prenatal diagnosis is determined by balancing the risk of the birth of an abnormal child against the risk of an investigative procedure.
The general indications of prenatal diagnosis include maternal age and the results of noninvasive serum biochemical screening.
Specific indications include a positive family history and the birth of a previous child affected by a particular ic disease.
2. Methods for obtaining fetal tissues for prenatal diagnosis
To perform prenatal diagnosis, fetal-derived tissues must first be obtained. All of monly used methods that yield fetal tissues are invasive.
A. Amniocentesis
Amniocentesis is the withdrawal of amniotic fluid from the amniotic sac surrounding the fetus. For over two decades this has been the primary technique utilised for the diagnosis of fetal ic disorders.
Traditionally amniocentesis has been performed around 15 to 16 weeks gestation. At this time the uterus is easily accessible to a transabdominal approach, and a sufficient volume of amniotic fluid (approximately 200 ml) exists to permit 20 to 30 ml to be withdrawn safely.
Amniocentesis is normally performed as an outpatient facility. An ultrasound examination is normally done immediately before the procedure to evaluate fetal number and viability, perform fetal biometric measurements, establish placental location, and estimate amniotic fluid volume.