Gestational dating ultrasound
It takes about 30 seconds to draw up the 20m L of straw coloured fluid required for analysis.The volume of fluid aspirated is about 1/6th of that present around the fetus and this is naturally replaced over the next 24 hours. An amniocentesis is usually performed between 15 and 18 weeks gestation.
If the results do come back showing a high probability, the genetic counsellor can assist in explaining the next steps. The test is performed at the ultrasound clinic by an Obstetrician Gynaecologist Sonologist (specialist ultrasound doctor).
With ultrasound control, a fine needle is then guided into the placenta and a biopsy of placenta tissue (chorionic villi) is taken.
The needle itself is at all times well distanced from the baby.
It is covered with a disposable latex sheath and lubricating gel, then gently placed into the vagina.
The probe sits in the vagina throughout the examination which usually takes between 10-15 minutes.