The optimal therapeutic management of patients with antiphospholipid syndrome (APS) during pregnancy is debatable. In the present prospective cohort study the use of a low molecular weight heparin (LMWH) (nadroparin), administered alone twice daily in 30 pregnant women who were diagnosed with APS on the basis of the current classification criteria, is evaluated. Dosage was adjusted according to anti-Xa levels in the patients as the pregnancies progressed. Three women, in whom an important gradual fall in platelet count in the first trimester did not respond to increased nadroparin doses, were shifted to a second-line treatment protocol. Fetal loss occurred in two of the 27 remaining women (7.40%), while 25 (92.59%) delivered 25 live infants, between the 32nd and 40th weeks of gestation. No fetal problems were registered during pregnancies, while maternal complications occurred in two of the 25 patients (8%). Moreover, there were no thrombotic events in any of the women during the study. Patient compliance was good and only minor side-effects were reported. The results of this study indicate that nadroparin alone is useful and safe in the management of pregnant patients with APS. However, in consideration of the good pregnancy outcome obtained in patients with only pregnancy morbidity when heparin and aspirin were used together, other studies comparing nadroparin twice daily with once daily plus Aspirin would be useful to ascertain which is more effective in these patients.