 The objective of this study is to test the efficacy of low-dose aspirin 160 mgday, given bedtime and started early during pregnancy 15 6 weeks of gestation in nulliparous pregnant women selected as high-risk by the presence of a bilateral uterine artery notch andor bilateral uterine artery PI 1.7 during the first trimester ultrasound scan 11-136 weeks, to prevent the occurrence of pre-eclampsia or small for gestational age at birth. 