Abdominal ultrasound during pregnancy: what to expect
Ultrasound scans work by emitting high-frequency sound waves, which are sent through a pregnant woman's body using a handpiece called a transducer. These sound waves are reflected back from the solid tissues of the developing baby and translated into images on a computer screen. There is no radiation involved in ultrasound, only waves.
During the hour before an abdominal ultrasound scan, you will be asked to drink several glasses of water and avoid emptying your bladder for better pictures. You may find this a little uncomfortable, but when your bladder is full, the ultrasound waves are reflected through this water-filled window lying immediately over the uterus and tiny baby, producing much clearer pictures.
You will be asked to lay down and lubricating gel is smeared onto the lower part of your abdomen to ensure good contact with the transducer. The ultrasound tech then moves the transducer smoothly forwards and backwards to produce ultrasound images on a computer screen.
How scans are used:
5-8 weeks: pregnancy viability scan shows sac in uterus; after 6 weeks fetal pole and heartbeat detectable
11-14 weeks: nuchal fold translucency scan screens for Down's syndrome; dates pregnancy
12-14 weeks: scan confirms growth, heartbeat and brain formation
20 weeks: detailed anatomy-heart, kidney, bladder, spine, brain, limbs. Checks the position of placenta
30 weeks plus: detailed scans to detect placental problems, intra-uterine growth retardation and volume of amniotic fluid