Pregnancy associated plasma protein A (PAPP-A)

PAPP-A test is one of the three tests conducted during the first few weeks (11 to 14 weeks) of pregnancy, also referred to as the first-trimester screening. The other two tests are the NT scan and HCG test.

PAPP-A is an established marker for trisomy 21 (Down syndrome). Your doctor may advise the PAPP-A test to check for this condition in your baby.

This test is also done for the following reasons:

• To assess the risk of Edwards syndrome (trisomy 18) in the developing baby
• As a significant predictor of adverse pregnancy outcomes such as increased risk of developing preeclampsia, a condition in which women have high BP in the later months of pregnancy. (Read more: Gestational hypertension symptoms)
• To assess the probability of foetal complications such as preterm birth, stillbirth, growth restriction in the baby or death.

You need not do any special preparation for the PAPP-A test. It is not necessary to fast either. Inform your doctor if you or any member of your family has any genetic disorders. The risk of acquiring a chromosomal disorder is higher in such cases.

It is a simple blood test for which a technician will withdraw about three to five mL of blood from a vein in your arm. Alternatively, the required amount of blood will be collected by a finger-prick. 

After the test, you may notice a light bruise around where the blood is drawn, though it will fade away in a few hours. If the bruise does not go away, inform your doctor.

PAPP-A results are written in terms of multiples of meridian that is how much the results deviate from a median value.

Normal results:

PAPP-A values greater than or equal to 0.5 multiple of median (MOM) is considered normal. Normal result indicates that you have a low likelihood of getting high BP in later months of pregnancy and your baby would not have any chromosome disorders (Down syndrome and Edwards syndrome).

Abnormal results:

PAPP-A values lower than 0.5 MOM are considered abnormal. Abnormal PAPP-A value is associated with a higher incidence of preterm birth, growth restriction and death in babies with a good chance that the mother would develop high BP during the later months of pregnancy.

Although the first-trimester screening (including the other two tests in combination with PAPP-A) can identify the majority of complications (about 85% women carrying babies with Down syndrome and 75% with Edwards syndrome), false-positive results are seen in 5%-10% of normal pregnancies. Therefore, it means that the test may be positive, but the pregnancy outcome may be uneventful.

Conversely, not all positive tests may be diagnostic of foetal abnormalities. Although they indicate a higher risk, the probability of having a baby with a chromosomal defect occurs only in a small section of women with a positive screen test. Similarly, low concentrations of PAPP-A in the maternal blood are a poor predictor of future adverse pregnancy outcomes.

So, even if the test result is positive or abnormal, confirmatory tests may have to be performed. Your doctor will precisely explain what the results mean for you.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.