The effect of additional treatments combined with conventional therapy on pregnancy outcomes was examined in high-risk primary antiphospholipid syndrome (PAPS) patients to identify the most effective treatment strategy. The study's inclusion criteria were (1) positivity to lupus anticoagulant alone or associated with anticardiolipin and/or anti-β2 glycoprotein I antibodies; (2) a history of severe maternal-foetal complications (Group I) or a history of one or more pregnancies refractory to conventional therapy leading to unexplained foetal deaths not associated with severe maternal-foetal complications (Group II). Two different additional treatments were considered: oral-low-dose steroids (10-20 mg prednisone daily) and/or 200 to 400 mg daily doses of hydroxychloroquine and parenteral-intravenous immunoglobulins at 2 g/kg per month and/or plasma exchange. The study's primary outcomes were live birth rates and pregnancy complications. A total of 194 pregnant PAPS patients attending 20 tertiary centres were retrospectively enrolled. Hydroxychloroquine was found to be linked to a significantly higher live birth rate with respect to the other oral treatments in the Group II patients. The high (400 mg) versus low (200 mg) doses of hydroxychloroquine (p = 0.036) and its administration before versus during pregnancy (p = 0.021) were associated with a significantly higher live birth rate. Hydroxychloroquine therapy appeared particularly efficacious in the PAPS patients without previous thrombosis. Parenteral treatments were associated with a significantly higher live birth rate with respect to the oral ones (p = 0.037), particularly in the Group I patients. In conclusion, some additional treatments were found to be safe and efficacious in high-risk PAPS pregnant women.