The aim of this systematic review was to evaluate the efficacy of isoxsuprine (1-(4-hydroxyphenyl)-2-(1-methyl-2-phe-noxyethylamino)-1-propanol, CAS 395-28-8), a tocolytic agent used in both preterm labour and risk of abortion. Two analyses were conducted on data reporting the use of isoxsuprine in the prevention of preterm delivery. The first analysis examined two double-blind studies to determine the effect of isoxsuprine compared to placebo. The second analysis reviewed data from 25 publications containing individual and general patient data. Main outcome measures included delay of pregnancy and patient outcome. Analysis of double-blind studies demonstrated a positive outcome with isoxsuprine in 92% of cases compared to placebo control (44.4%, p < 0.001). This beneficial effect was maintained when either risk of abortion (92.5% in isoxsuprine treated compared to 46.4% in placebo, p < 0.001) or risk of premature delivery (89.5% in isoxsuprine treated compared to 29.4% in placebo, p < 0.001) was examined. Secondary analysis of individual patient data also revealed a beneficial effect of isoxsuprine in prolonging pregnancy in 54.5% of women at risk of abortion and in 82.3% of women at risk of premature delivery. Combination of individual and general data revealed a beneficial effect of isoxsuprine in 77.3% of cases at risk of abortion and 89% for risk of premature delivery. These findings provide preliminary evidence in favour of the effectiveness of isoxsuprine in prolonging pregnancy in women at risk of abortion or premature delivery.