Stepten £ staying pregnant your 12-week scan
Between 11 and 13 weeks you will be offered a routine ultrasound scan, which helps to monitor fetal growth and development. This will also be used to confirm your baby’s estimated date of delivery (EDD).
Ultrasound scans work by sending high-frequency sound waves through your body using a small, handheld probe called a transducer. Echoes produced as the pulses strike structures are converted into electrical signals, which are processed to produce an image. Before you have an abdominal ultrasound scan you will be asked to drink several pints of water and to avoid emptying your bladder. Your expanded bladder reduces the space in the lower abdomen and pushes the uterus upwards, making it easier for the sonographer to get a clear image. He or she will take key measurements – the circumference of the head
and abdomen and length of the femur (thigh bone) -and the relationship between these gives an indication of growth. Your baby’s heartbeat will also be monitored and you will be able to see it beating fast on the screen.
Ultrasound scans can detect most fetal abnormalities and they identify disorders that might put the baby at risk. Not everything can be picked up by a scan, but the detection rate for anencephaly (brain defect), for example, is 98 per cent, and for spina bifida it is 80 per cent. Screening is done for all types of chromosomal disorders, in particular Down’s syndrome (see below).
Multiple pregnancies are often diagnosed during the 12-week scan, although they can be detected earlier if you have a six-week scan (usually following IVF treatment) when two or more fetal sacs will be visible in the uterus.