Diagnostic methods and tools relating to diagnosing whether a pregnant subject is at risk for developing preeclampsia and/or early-onset preeclampsia within a short period of time. The methods include determining the amounts of the biomarkers sFlt-1 or Endoglin and PIGF in a first and a second sample of said subject, said first sample being obtained prior to said second sample; calculating a first ratio from the amounts of sFlt-1 or Endoglin and PIGF determined in the first sample, and a second ratio from the amounts of sFlt-1 or Endoglin and PIGF determined in the second sample; and comparing the value of the first and the second ratio, whereby a subject being at risk for developing preeclampsia within a short period of time is diagnosed if the value of the second ratio is increased compared to the value of the first ratio by a factor of at least about 3.