Background‘Systemic autoimmunity associated with rheumatoid arthritis’ (RA), is a pre-clinical stage preceding the onset of clinical RA, characterised by the presence of autoantibodies, such as anti-citrullinated protein antibodies (ACPA) or anti-carbamylated protein antibodies (antiCarP). Breastfeeding has been proposed as a protective factor for RA development,1 but there are some controversies.2 To establish the causal role of a putative risk factor, longitudinal studies are needed, in particular in the pre-stages of RA development.ObjectivesTo study the association between breastfeeding and the development of systemic autoimmunity associated with RA.MethodsThis ongoing prospective study includes individuals genetically at risk of developing RA, namely first-degree relatives of RA patients (RA-FDR). Individuals without clinical evidence of RA were enrolled, and assessed yearly clinically and biologically. We included all RA-FDR women with available ACPA status (anti-CCP 2, 3.1 or 3.0) and information about breastfeeding. The primary outcome was ACPA positivity. The exposure of interest was breastfeeding and duration of breastfeeding (categorised as 0, 1–7 and ≥7 months). The presence of antiCarP was a secondary outcome. We used logistic regression to analyse univariable and multivariable associations.ResultsA total of 882 women were included, of which 57 (6%) were ACPA positive. The characteristics of ACPA positive and negative participants were balanced, except for an older age in ACPA positives (median 52 versus 45 years; table 1). In the univariable analysis, ACPA positivity was not significantly associated with breastfeeding (OR 1.5, p=0.16) or with breastfeeding duration (OR=1.8, p=0.14). In the multivariable analysis adjusted by age, smoking, number of pregnancies and years of education, there was a weak, but not significant, association between breastfeeding for more than 7 months and ACPA positivity (OR 2.16, p=0.10). Among 728 women with available antiCarP results, 70 (10%) were positive, of which 27 (40%) breastfed. Breastfeeding for more than 7 months was not significantly associated with antiCarP in univariable or multivariable analyses (OR 1.3, p=0.52 and OR 1.9, p=0.16, respectively).Abstract SAT0692 – Table 1General characteristics of RA-FDR women, n=882ConclusionsAmong women at risk of RA, breastfeeding was not associated with the presence of ACPA or antiCarP. Our results do not support a protective role of breastfeeding in the development of systemic autommunity associated with RA.References1 Orellana C, et al. Ann Rheum Dis2017;76:1845–52.2 Berglin E, et al. Scand J Rheumatol2010;39:454 -60.Disclosure of InterestNone declared