Pregnancy Associated Plasma Protein A (PAPP-A)

A pregnant woman at a doctor's clinic

Anomalies in Pregnancy Associated Plasma Protein A (PAPP-A) levels can be an indicator for not only some pregnancy complications but also for potential chromosomal disorders. Monitoring of PAPP-A levels in pregnant women can aid detect women who are at a greater risk of abnormal obstetric results. Lower the levels, higher are the chances of adverse pregnancy outcomes.

What is PAPP-A?

PAPP-A stands for Pregnancy Associated Plasma Protein A. It is a protein that is released by the placental trophoblasts during pregnancy. It is believed to play an essential role in the early growth of placenta and formation of the placental bed. The PAPP-A levels are tested during the screening tests conducted in the first trimester of pregnancy, that is between 11 to 13 weeks of gestation. Several pregnancy problems such as greater risk of fetal loss, premature delivery, still birth, gestational hypertension, low birth weight, fetal development restrictions, pre-eclampsia, placental abruption are believed to be associated with low levels of PAPP-A. Studies have also indicated that low levels of PAPP-A can be linked to higher risk for Down’s Syndrome and certain structural aberrations in the foetus.

What is a Normal PAPP-A level?

The two hormones which are measured during the combined screening test of PAPP-A levels, around 12 weeks of pregnancy, are MoM value and concentration (IU/L). MoM means multiple of the median or average of all the tests. MoM value of 1.00 is average, more than 1.00 is above average and less than 1.00 is below average. PAPP-A levels higher or equal to 0.5 MoM is taken as normal and if the levels are lower than 0.5 MoM, they are considered low.

PAPP-A Normal Range Chart

MoM Value PAPP-A Level
>=0.5 MoM Normal
< 0.5 MoM Low

Various studies show the pregnancy results of women with normal PAPP-A levels to be generally uneventful when compared to results of women with low PAPP-A level.

When will you Need a Growth Scan?

A pregnant woman holding an ultrasound scan

A growth scan is also called a positioning or foetal well-being scan. It is advisable to conduct a growth scan between 28 and 34 weeks of gestation. The technician or doctor, along with checking the growth of the baby, also measures the levels of amniotic fluid and the placenta. The position of the baby in the uterus is also checked. Through this scan, the head, thigh bone and abdomen of the baby are measured. Additional scans or more follow ups may be suggested even if the growth of the baby and the fluid levels are normal. This is because babies have growth spurts and repeated scans can monitor the growth of the baby more conclusively than a solo scan. In case of any concern, the subsequent follow ups will depend on individual’s condition.

What does a Low PAPP-A Mean?

A low PAPP-A means that the concentration of maternal serum PAPP-A is less than 0.5 MoM, between 11 to 13 weeks of pregnancy. The risk of complications during the pregnancy is increased with low PAPP-A levels. Pregnant women with PAPP-A level lower than 0.5 MoM need constant monitoring as they are believed to be at a higher risk for premature labour, intrauterine growth restriction, pregnancy induced hypertension and miscarriage. Researchers opine that lower the MoM value of PAPP-A, higher are the risks of poor pregnancy results.

How will you Know that your Baby is Growing Well Before and After the 34-Week Scan?

The first ultrasound or sonogram is conducted around 6 to 8 weeks of pregnancy. Through this ultrasound, the doctor gets to measure the growth of the baby, monitor the baby’s milestones, spot anomalies, calculate the due date, check for multiple pregnancies and determine the position of the placenta. A pregnant woman may be offered a combination of prenatal screening tests during the first trimester (between 11 to 14 weeks of pregnancy) which include pappa test, nuchal translucency ultrasound, hCG (human chorionic gonadotropin) to determine the probable risk of a chromosomal disorder in the baby. In case the screening test is positive, further specific diagnostic test like chorionic villus sampling (CVS), during the first trimester and amniocentesis, during the second semester are suggested. During the second trimester, pregnant women may also be offered maternal serum test and foetal DNA test.

Nearer to the due date (34 to 40 weeks), another growth scan is carried out to assess the development of the baby and to check the weight and position of the baby. This is ascertained by measuring the biophysical profile of the baby. One may be suggested additional scans during the third trimester, if there is any cause for concern. Regular scans are advised throughout the pregnancy if there are complications and high risk of abnormal obstetric results. Sometimes pregnant women develop gestational diabetes during the third trimester. A Doppler scan is usually suggested in view of such a development. If the doctor suspects the baby to be in a breech position, closer to the due date (around 37 weeks), he may perform a scan to determine this and then may go for a cesarean. A cesarean section may also be performed, if a pregnant woman is diagnosed with placenta previa where the placenta is very close or over the cervix.

A pregnant woman with low a PAPP-A level may be suggested additional scans for early and prompt detection and management of probable adverse pregnancy results. Studies have still not established a conclusive connection between a low PAPP-A and the amplified risk of pregnancy complications. Therefore, it is also believed that these screening tests have a low predictive accuracy and are inconclusive. But the test may still be an indicator of some chromosomal abnormalities. So it is advisable to consult and discuss the results with your doctor at length.

Pregnancy brings with it a whole new set of changes and problems to watch out for, and regular testing and scans in this period are planned in order to keep a tab on all the stats which indicate the wellness of the baby and the mother. If is important to ensure that you go for all the prescribed tests and scans, and discuss and anomalies or discomfort with your doctor.

Also Read:

Double Marker Test in Pregnancy
First Trimester Scans
How to Maintain Progesterone Levels during Pregnancy