Pregnancy and postpartum are vital times of greater vulnerability to suffer a decompensation of bipolar disorder (BD). Methods: A systematic literature search was performed on public electronic medical databases, following PRISMA guidelines. Studies were included if they reported postpartum relapse in patients diagnosed with BD according to Diagnosis Statistical Manual (DSM) or International Classification Disease (ICD) criteria. Results: Sixteen articles describing 6064 deliveries of 3977 women were included in the quantitative analyses. The overall risk of postpartum relapse was 36.77%. The methodology of the studies, the diagnostic criteria, the discrimination between BD type I and II, and the origin of the sample were very heterogeneous. Conclusions: the rate of postpartum bipolar relapse is very high, as it is considered to be a critical period. It is especially important to detect decompensation in this period and to evaluate mood-stabilizing treatment, given the high risk of relapse concentrated in a short period.