506: The impact of low dose aspirin on preeclampsia biomarkers and fetal growth in low-risk women

To evaluate the impact of low dose aspirin (LDA) use in low-risk pregnancy on; (i) placental biomarkers PAPP-A and PLGF, (ii) systemic markers albumin creatinine ratio (ACR) and blood pressure, (iii) fetal growth parameters and (iv) placental histopathology. This was a secondary analysis including data from the primary site of the TEST RCT where 546 low-risk nulliparous women were randomised at 11-weeks to; (i) routine aspirin 75mg from 11 to 36-weeks; (ii) no aspirin; and (iii) aspirin based upon the preeclampsia Fetal Medicine Foundation screening test. At baseline women underwent assessment of blood pressure, PAPP-A, PLGF and ACR. These were repeated at 20-22 weeks (9-10 weeks post LDA commencement) in addition to ultrasound assessment of fetal growth, which was repeated again at 32-weeks. Gross and histopathological placental analysis were performed including assessment of fetalplacental weight ratio, cord coiling, fetal and maternal vascular malperfusion, maturation defects and villitis. Aspirin and non-aspirin groups were compared using logistic regression. 445 subjects were included (LDA n=163 no LDA=282), with the LDA group comprising n=13 from the screen positive arm and 150 from the routine LDA arm. As rates of smoking and weight differed at baseline, these were controlled for in analyses. LDA was associated with a significant increase in abdominal circumference (p=0.04) and femur length (p=0.01) at 20-22 weeks (p=0.04), which was not persistent at 32-weeks (p=0.60). There was no difference in birthweight 3520.3g (507.6) vs. 3470.7g (523.0) p=0.70 [Table 1]. Although there was an increased fetal placental weight in the aspirin group (7.5 vs. 7.3), this did not reach significance p=0.05. There was no difference between groups in relation to blood pressure, serum and urine biomarkers or histopathological placental findings. Low dose aspirin appears to promote fetal growth in low-risk nulliparous women between the first and second trimester, which is not evident thereafter. Our study did not demonstrate an impact of aspirin on placental or systemic biomarkers assessed.