PGF and preeclampsia: In addition, the relationship of first trimester PAPP-A to serial levels of placental growth factor (PlGF) and serial ratios of sFlt-1 to PlGF were also explored, as studies have shown that PlGF is significantly lower in preeclampsia [9] and the ratio of sFlt-1/PlGF is also significantly elevated in preeclampsia [10,11], prior to the onset of clinical signs.