The developing fetus is surrounded by fluid in the womb called Amniotic Fluid. This has a number of important functions including cushioning the baby, allowing fetal movement and growth and the provision of nutrients to help the baby grow. The fluid is inhaled and swallowed by the fetus and also allows waste products from the fetus such as urine to be removed.

Amniocentesis is a procedure performed under ultrasound guidance whereby the fluid is sampled by introducing a fine needle either through the mother’s abdomen or via the vagina into the amniotic cavity. Ultrasound is essential to avoid the needle damaging the fetus, placenta or maternal structures such as bowel. There is also a risk of miscarriage.

The cells in the fluid may be analysed for genetic testing to identify abnormalities such as Down’s Syndrome, neural tune defects such as Spina Bifida, metabolic disorders and other genetically inherited disease.

Other methods for prenatal diagnosis include :

• Chorionic Villus Sampling (CVS)
• Umbilical cord blood sampling
• Diagnostic Obstetric Ultrasound including Nuchal Fold measurement
• Maternal Blood Sampling eg human chorionic gonadotrophin