Antenatal screening

An ultrasound scan on a pregnant woman

Antenatal screening is used to identify any possible risks to the mother or foetus during pregnancy or to identify health issues that will affect the baby.

If a risk is identified, then further tests can be carried out and a prenatal diagnosis given.

Different techniques are used for a range of purposes.

Ultrasound imaging

Pregnant women are routinely given two ultrasound scans during their pregnancy:

  • Dating scan
    • carried out between 8 and 14 weeks
    • ussed to determine stage of pregnancy and due date
    • used with tests for marker chemicals which vary during pregnancy
  • Anomaly scan
    • carried out between 18 and 20 weeks
    • may detect any serious physical abnormalities

Blood and urine tests

Regular checks are carried out on the mother’s urine and blood to monitor concentrations of marker chemicals which can identify a possible condition.

These chemicals vary normally during pregnancy. This is why they are used in conjunction with scans, as measuring chemicals at the wrong time can lead to a false positive result.

Changing chemistry in blood and urine can be used to indicate pre-eclampsia and Down's syndrome.