placenta associated plasma protein A (PAPP-A)

Last reviewed 01/2018

Pregnancy-associated plasma protein A (PAPP-A)

Blood levels of PAPP-A are measured as part of the combined pregnancy screening offered between 11 weeks + 2 days and 14 weeks + 1 day of pregnancy.

• PAPP- A is a large glycoprotein produced by the placenta and decidua thought to have several functions including:
  • prevention of recognition of the fetus by the maternal immune system
  • matrix mineralisation
  • angiogenesis
    
    
• a low PAPP- A is descriptive of poor early placentation and may result in adverse pregnancy outcomes such as (1,2):
  • mid trimester miscarriage
  • fetal growth restriction
  • intrauterine fetal death
  • preterm birth
  • preeclampsia
  • can be associated with Down's Syndrome (6)

Assisted reproductive technology ( ART ) pregnancies have reduced first trimester screening PAPP- A levels leading to an increased likelihood of receiving a false- positive result and having a chorionic villus sampling /amniocentesis. Lower PAPP -A may reflect impairment of early implantation with some forms of ART (3)

An abnormal PAPP -A is defined as a maternal serum PAPP -A concentration < 5 th percentile, with increased frequency of adverse obstetrical outcomes noted below this level (4)

• MoM stands for multiple of the median, or average, of everyone's results
  • a MoM of 1.00 is average; higher than 1.00 is above average; and lower than 1.00 is below average
  • recommended for additional screening if PAPP- A levels are below 0.40 MoM,as these are more likely to be associated with fetal growth restriction (6)

Although the risk of pregnancy complications is increased with PAPP-A < 5 th percentile, a PAPP-A less than the 1 st percentile offers a particular significant risk to the pregnancy (5)

NB: Accurate maternal weight should be confirmed upon return of the first trimester screen result as this has significant effect of PAPP-A concentrations

Reference:

• Gagnon A, Wilson RD, Audibert F, Allen VM, Blight C, Brock JA, et al. Obstetrical complications associated with abnormal maternal serum markers analytes. J Obstet Gynaecol Can. 2008; 30:918 –49.
• Yaron Y, Heifetz S, Ochshom Y, Lehavi O, Orr- Urtreger A. D ecreased first trimester PAPP -A is a predictor of adverse pregnancy outcome . PrenatDiagn 2002; 22:778 -82.
• Amor DJ, Xu JX, Halliday JL, Francis I, Healy DL et al. Pregnancies conceived using assisted reproductive technologies (ART) have low levels of pregnancy -associated plasma protein -A (PAPP- A) leading to a high rate of false -positive results in first trimester screening for Down syndrome. Hum Reprod 2009 ; 24: 1330 -1338.
• Dugoff L., Hobbins JC, Malone FD et al. First Trimester maternal serum PAPP -A and free -beta subunit human chorionic gonadotropin concentrations and nuchal translucency are associated with obstetric complications: A population -based screening study (The FASTER Trial). AJOG. 2004; 191:1446 -51
• Krantz D, Goetzl L, Simpson JL. Associa tion of extreme first -trimester free human chorionic gonadotropin -beta, pregnancy -associated plasma protein A, and nuchal translucency with intrauterine growth restriction and other adverse pregnancy outcomes. AJOG 2004; 191:1452.
• Hampshire Hospitals NHS Foundation Trust. Low PAPP - A (Accessed 28th September, 2016)