Relationship between nulliparity and preeclampsia may be explained by altered circulating soluble fms-like tyrosine kinase 1

Objective: To test the hypothesis that the risk of preeclampsia in nulliparous women may be due to an anti-angiogenic state. Methods: Maternal serum samples obtained in the third trimester from nulliparous (n = 86) and multiparous (n = 165) singleton uncomplicated pregnancies were analyzed for levels of angiogenic factors -soluble fms like tyrosine kinase 1 (sFlt1) and placental growth factor (PlGF) by enzyme-linked immunosorbent assay (ELISA). Results: For nulliparous and multiparous pregnancies, serum sFlt1 levels were 12 732 +/- 832 and 10 162 +/- 666 (p = 0.020), serum PlGF levels were 215 +/- 15 and 249 +/- 14 (p = 0.093) (all reported as mean SD in pg/ml) and mean ratios of sFlt1/PlGF were 93 +/- 12 and 62 +/- 5 (p = 0.023), respectively. Adjustment for maternal age and fetal birth weight did not alter the results. Conclusions: Nulliparous pregnancies had higher circulating sFlt1 levels and sFlt1/PlGF ratios than multiparous pregnancies, suggesting an association with an angiogenic imbalance. Taken together with the pathogenic role of anti-angiogenic factors in preeclampsia, our data may be one explanation for the epidemiological observation that nulliparity is a risk factor for the development of preeclampsia.