Quadruple screening test

The quadruple screening test is offered to pregnant women in the second trimester (from 14 to 20 weeks’ gestation). It assesses the chance of a pregnancy being affected by trisomy 21 (Down syndrome). It does not screen for trisomy 18 (Edwards syndrome) or trisomy 13 (Patau syndrome).

Quadruple screening is usually offered when combined first-trimester screening cannot be offered because:

• the woman presents later than expected to maternity services;
• the nuchal translucency measurement cannot be obtained; or
• during ultrasound examination, the fetal crown-rump length is found to be greater than 84mm, and the head circumference is found to be between 101mm and 172mm.

Four biochemical markers are analysed and combined with maternal age to generate a quadruple screening test result. These comprise:

• alpha-fetoprotein (AFP);
• human chorionic gonadotropin (hCG) or free bhCG;
• inhibin A; and
• unconjugated oestriol (uE3).

A maternal venous blood sample is required for analysis, as well as an accurate measurement of the fetal head circumference. The measurement must be recorded on the test form that goes with the sample to the biochemistry laboratory.

If the screening returns a low-chance result for Down syndrome, no further action is required.

Where a higher-chance result is given (from 1 in 2 to 1 in 150), further assessment should be offered. This may include further ultrasound imaging in a specialist fetal medicine unit, non-invasive prenatal testing or diagnostic testing requiring chorionic villus sampling or amniocentesis.

For further information, see Patient with a higher-chance first-trimester combined screening result.

• The quadruple screening test is offered to pregnant women between 14 and 20 weeks’ gestation.
• Quadruple screening is usually undertaken when combined first-trimester screening cannot be offered because, for example, the nuchal translucency measurement cannot be obtained.
• The screening test combines information from a maternal blood test and an ultrasound scan to determine the chance that the fetus is affected by trisomy 21 (it does not screen for trisomies 18 or 13).
• Where a higher-chance result is given (from 1 in 2 to 1 in 150), further assessment should be offered.

For clinicians

• Improving News Delivery in Ultrasound (INDIRA): Consensus guidelines on the communication of unexpected news via ultrasound (PDF, 44 pages)

For patients

• Antenatal Results & Choices
• Down’s Syndrome Association