The impact of various entities of antiphospholipid antibodies positivity on adverse pregnancy outcome. An epidemiological perspective

•Antiphospholipid antibodies in pregnancy increase incidence of adverse pregnancy outcomes, even in asymptomatic carriers.•Classifications of antiphospholipid antibody profile are poorly associated with the burden of obstetric complications.•Connective tissue diseases associated with antiphospholipid antibodies carry additional risk of adverse obstetric outcome. The aim of the study was to evaluate the rate of obstetric complications and the burden of obstetric outcomes in antiphospholipid syndrome (APS), non-criteria APS and asymptomatic antiphospholipid antibodies (aPL) carriers. From 2013–2018, 163 pregnant subjects with aPL antibodies and 785 controls were enrolled. Penalized logistic regression was used to compare obstetric complications. Cases included 62 complete APS (38 %), 48 non-criteria APS (29.4 %) and 53 (32.5 %) asymptomatic aPL-carriers. Connective tissue diseases (CTDs) were diagnosed in 31.3 % of cases. The rate of high-risk aPL profile was higher (p < .01) in APS (67.7 %) compared to non-criteria (14.6 %) and aPL-carriers (9.4 %). Double/triple positivity was 33.9 % (p < .05 compared to non-criteria and aPL-carriers) in APS, 10.4 % in non-criteria and 9.4 % in aPL-carriers. The rate of adverse pregnancy outcomes were 5.6 % in controls, 41.9 % (adj.OR = 6.95 %CI = 2.7−13.5) in APS, 25 % (adj.OR = 4.4,95 %CI = 2−9.4) in non-criteria and 28.3 % (OR = 4.95 %CI = 1.8−8.8) in aPL-carriers. CTDs were independently associated with an increased risk of adverse obstetric outcomes (OR = 2.8,95 %CI = 1.36–5.89). The attributable fraction (AF) of adverse obstetric events was higher among low-risk antibodies compared to high-risk (AF = 0.27,95 %CI = 0.22−0.31 vs AF = 0.16,95 %CI = 0.16−0.2,p < .01) and among single positivity compared to double/triple positivity (AF = 0.32,95 %CI = 0.26−0.37 vs AF = 0.11,95 %CI = 0.09−0.13,p < .01) suggesting that low-risk subjects are responsible for a high burden of obstetric complications.