Placental insufficiency is the source of preeclampsia (PE) and intrauterine growth retardation (IUGR). Current data demonstrate a significant beneficial effect of prophylactic use of aspirin on the recurrence of placental insufficiency and its complications, mainly preeclampsia, when started early in pregnancy. However, there is a significant heterogeneity in medical practice in Canada and around the world in terms of the dose of aspirin used.

The objectives of this study are: 1) Evaluate whether a dose of 160 mg of aspirin is associated with greater improvement in placental function assessed by biochemistry (sFlt-1 and endoglin) and ultrasound (uterine artery Doppler) than a dose of 80 mg in women with a history of PE, 2) Assess whether the change is dependent on platelet aggregation measured by a test used in several Canadian centers (PFA-100).

Many studies suggest that aspirin (acetylsalicylic acid) at low dose significantly reduces the incidence of preeclampsia. More recent data have shown that, when administered before 16 weeks of pregnancy, aspirin can prevent over 50% of preeclampsia, severe preeclampsia, and IUGR but also a significant proportion of the rate of preterm births. Current data also demonstrate a beneficial effect of prophylactic use of aspirin when started early in pregnancy in populations composed of high-risk patients with a history of preeclampsia and / or other pregnancy complications related to poor placental function.

Beside, many clinicians are already using aspirin in the context of a proven benefit. However, the usual dose prescribed in Canada today is 80 mg while the most favorable studies have used a slightly higher dose of aspirin (100 mg).

Moreover, it has been demonstrated that the time of day during which aspirin was administered was also a very important factor regarding the effect on blood pressure and adverse outcomes of the majority of pregnancy. Yet the majority of studies in this context have not specified the time of day at which aspirin was or had been taken, possibly underestimating the effect thereof.

Inclusion Criteria:

• Gestational age between 10 0 / 7 and 13 6 / 7 weeks
• History of preeclampsia (as defined by The Society of Obstetricians and Gynaecologists of Canada) confirmed by medical records

Exclusion Criteria:

• Negative Fetal Heart
• Multiple pregnancy
• Anaphylactic allergy to lactose
• Kown coagulopathy (antithrombin III deficiency, factor V Leiden, antiphospholipid syndrome, the prothrombin mutation, deficiency of protein S or protein C)
• Use of heparin or other anticoagulants.
• Contraindications to aspirin
• Severe fetal abnormality (cystic hygroma, nuchal translucency> 95th percentile, anencephaly, etc.)
• History or active peptic ulcer