This article is a review of the literature assessing pregnancy outcomes and the effect of metformin treatment among women with polycystic ovary syndrome (PCOS). A review of research published in English was undertaken using PubMed and MEDLINE databases. The weight of the available evidence suggests that pregnant women with PCOS are at an increased risk of developing gestational diabetes, hypertensive disorders of pregnancy, preterm birth and early pregnancy loss. Obesity is a contributory factor for the increased risk of gestational diabetes in this group of women and is estimated to affect 5-40% of pregnant women with PCOS. The prevalence of other obstetric complications is estimated at 10-30% for gestational hypertension, 8-15% for pre-eclampsia and 6-15% for preterm birth. The association between PCOS and early pregnancy loss may not be direct, wherein the presence of PCOS-associated hyperinsulinemia, leading to hyperandrogenemia, has been implicated in the pathophysiology of early pregnancy loss. Apart from the role of metformin in improving the metabolic consequences accompanying PCOS, it has been shown to improve pregnancy rates in women with PCOS who are resistant to clomiphene citrate. In conclusion, pregnancy in women with PCOS is associated with adverse obstetric outcomes (multiple adverse obstetric risk). Whether metformin should be administered throughout pregnancy still remains controversial. Further prospective studies that foster a larger number of participants and adjust for all potentially confounding factors are needed.