Preeclampsia Sequential Screening Using Angiogenic Factors During First Trimester of Pregnancy

All the data required to carry out this study, including those derived from sonographies and blood tests, will be collected during the normal pregnancy control, without further appointments. A blood test will be requested in all pregnant women in the first appointment of pregnancy control between 9 and 13 weeks, to determine risk of chromosomal disorders according to the national protocol and it will be used this same sample to analyze angiogenic factors without requiring new blood extractions. In the first-trimester scan, the mean uterine arteries pulsatility index will be determined, as well as mean arterial pressure. In this visit, the patient will be asked about her medical history. We will offer the patients the inclusion to our study in that moment; those who agree to participate in the study will sign the informed consent. In the participants, the initial risk of PE will be calculated using maternal medical history, MAP, UTPI and PAPP-A (already used in aneuploidies screening), using the software validated to each laboratory. Patients will be classified into 3 groups: * Low risk of PE (\<1/500) * Intermediate risk of PE (between 1/50 and 1/500) * High risk of PE (\>1/50) In those patients classified as intermediate and high-risk, PlGF and s-Flt-1 will be determined from the blood samples kept in biobanks of each hospital according to the current legislation. SFlt-1 results will be analyzed at the end of the study in order to decrease the cost because there will not be used to make clinical decisions. PlGF in high-risk patients will not be considered either to reclassify those patients. In both cases, the diagnostic efficiency will be analyzed at the end of the study. Patients in the intermediate-risk group (1/50-1/500) will be reclassified after adding PlGF levels in the predictive algorithm in 2 groups: Low risk of PE (\<1/160) and High risk of PE (\>1/160). To the patients classified as high risk at any of the steps, will be offered prophylactic treatment with AcetylSalicylic acid (ASA) (150mg/24h) until 36 weeks of pregnancy, if there is not a contraindication. All data from eligible patients will be analyzed. A bivariant statistical analysis will be performed in order to assess the relationship between dependent variables (diagnose of PE and/or IUGR) and the other variables included in this study