Objective: The purpose of this article is to review the literature assessing foetal and maternal pregnancy outcomes in women with PCOS who used metformin during pregnancy. Study Design: A literature search was conducted using MEDLINE, with analysis of 25 studies that recorded neonatal and maternal outcomes in women who used metformin during pregnancy. The outcomes assessed in this review include congenital deformities, miscarriages, preterm labour, gestational diabetes (GDM) and pregnancy induced hypertension (PIH). Results: We found that the use of metformin throughout pregnancy correlated with decreased rates of preterm labour, GDM and PIH. Conflicting evidence exists over whether metformin use during pregnancy reduced miscarriage rates. The use of metformin during pregnancy did not increase teratogenicity risks. Conclusion: The use of metformin throughout pregnancy is associated with decreased rates of preterm labour, GDM, and PIH. However, more randomised controls involving larger numbers of participants are required for more definitive results.