Placental growth factor (PlGF) is expressed in the placenta and is essential for placental angiogenesis and maintenance of the maternal endothelium.3,4 In a healthy pregnancy, PlGF concentration increases until about pregnancy week 30, reflecting placental angiogenesis and a healthy endothelium (see High PlGF bioavailability).5

However, in pregnant women destined to develop preterm pre-eclampsia, an increased expression of an anti-angiogenic factor, soluble fms-like tyrosine kinase-1 (sFlt-1), binds to free PlGF to form a complex, sFlt-1:PlGF, and lowers the concentration of free PlGF in the maternal circulation, reducing its ability to signal through the Flt-1 receptor (see Low PlGF bioavailability).6,7

Reduced bioavailability of PlGF (also known as angiogenic imbalance) leads to widespread maternal uteroplacental and endothelial dysfunction and the clinical manifestations of preterm pre-eclampsia, including vasoconstriction and end-organ injury.8, 9

Prospective longitudinal studies have demonstrated that women who develop pre-eclampsia have decreased circulating levels of bioavailable PlGF several weeks before the onset of clinical signs when compared with pregnant women with a normal outcome.7

PlGF testing helps identify the presence of pre-eclampsia and the risk for pregnancy complications. Measuring PlGF concentration on the Quidel Triage PlGF Test is helpful in anticipating and supporting a clinical diagnosis, assessing disease severity, and the risk for short-term delivery, and predicting adverse outcomes.12-15 PlGF test results fall within one of three discrete risk categories:

• PIGF <12 pg/mL – Highly abnormal and suggestive of patients with severe placental dysfunction and at increased risk for preterm delivery with pre-eclampsia.
• PlGF ≥ 12 pg/mL and < 100 pg/mL – Abnormal and suggestive of patients with placental dysfunction and at increased risk for preterm delivery with pre-eclampsia.
• PlGF ≥ 100 pg/mL – Normal and suggestive of patients without placental dysfunction and unlikely to progress to delivery with pre-eclampsia within 14 days of the test.

Performance characteristics11
PlGF measured in women with a singleton pregnancy and suspected pre-eclampsia after 20 and before 35 weeks of gestation has high accuracy for predicting pre-eclampsia needing delivery within 14 days or preterm.10

PlGF ≥100 pg/mL:
A normal maternal circulating level of PlGF (≥100 pg/mL) is strongly associated with the pregnancy not requiring delivery within 14 days with pre-eclampsia:

• Sensitivity, 96.0%
• Negative predictive value, 97.5%
• Long estimated time to delivery

PlGF <12 pg/mL:
A very low PlGF level (<12 pg/mL) is strongly associated with a need for preterm delivery:

• Sensitivity, 97.1%
• Negative predictive value, 94.2%
• Short estimated time to delivery

1. Redman CWG, Sargent IL. pre-eclampsia, the Placenta and the Maternal Systemic Inflammatory Response—A Review. Placenta. 2003 Apr;24 Suppl A:S21-7. 
2. Magee LA, et al. The 2021 International Society for the Study of Hypertension in Pregnancy classification, diagnosis & management recommendations for international practice. Pregnancy Hypertens. 2022 Mar;27:148-169.
3. Maglione D, et al. Two alternative mRNAs coding for the angiogenic factor, placenta growth factor (PlGF), are transcribed from a single gene of chromosome 14. Oncogene. 1993;8:925-931. 
4. Khaliq A, et al. Localisation of placenta growth factor (PIGF) in human term placenta. Growth Factors. 1996;13:243-250. 
5. Saffer C, Olson G, Boggess KA, Beyerlein R, Eubank C, Sibai BM; NORMALS Study Group. Determination of placental growth factor (PlGF) levels in healthy pregnant women without signs or symptoms of pre-eclampsia. Pregnancy Hypertens. 2013 Apr;3(2):124-132. 
6. Maynard S, et al. Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction, hypertension, and proteinuria in pre-eclampsia. J Clin Invest. 2003;111: 649-658. 
7. Levine R, et al. Circulating angiogenic factors and the risk of pre-eclampsia. N Engl J Med. 2004;350:672-683. 
8. Maynard SE, Karumanchi SA. Angiogenic factors and pre-eclampsia. Semin Nephrol. 2011 Jan;31(1):33-46. 
9. McMaster MT, Zhou Y, Fisher SJ. Abnormal placentation and the syndrome of pre-eclampsia. Semin Nephrol. 2004;24:540-547. 
10. Quidel Triage PLGF test Product Insert.
11. Chappell LC, Shennan AH. Diagnostic accuracy of placental growth factor in women with suspected pre-eclampsia: a prospective multicenter study. Circulation. 2013 Nov 5;128(19):2121-2131. 
12. Sibiude J, Tsatsaris V. Placental growth factor for the prediction of adverse outcomes in patients with suspected pre-eclampsia or intrauterine growth restriction. PLoS One. 2012;7(11):e50208. 
13. Parchem JG, Sibai BM; pre-eclampsia Triage by Rapid Assay Trial (PETRA) Investigators. Placental Growth Factor and the Risk of Adverse Neonatal and Maternal Outcomes. Obstet Gynecol. 2020 Mar;135(3):665-673. 
14. Duckworth S, Chappell LC. Diagnostic Biomarkers in Women With Suspected pre-eclampsia in a Prospective Multicenter Study. Obstet Gynecol. 2016 Aug;128(2):245-252. 
15. Duhig KE, Chappell LC; PARROT trial group. Placental growth factor testing to assess women with suspected pre-eclampsia: a multicentre, pragmatic, stepped-wedge cluster-randomised controlled trial. Lancet. 2019 May 4;393(10183):1807-1818.