Studies from several countries have reported occurrence of the highs (hypomanic symptoms) immediately after childbirth; however, questions remain about the relationship of the highs with mood disorders. This systematic review aims to clarify this relationship, critically review important aspects of the highs, and make treatment recommendations and suggestions for future research. The electronic databases of MEDLINE/PubMed, PsycINFO, CINAHL, Cochrane Database of Systematic Reviews, and Evidence-Based Medicine Reviews (EBMR) were searched using the keywords and their combinations: postpartum, euphoria, hypomania, and baby pinks. Reference lists of articles identified were also searched. Using the Highs scale, studies have found that 9.6-49.1% of postpartum women have hypomanic symptoms. Some but not all of the studies found an association of the highs with later depression. Symptoms of hypomania or mania are also common among women referred to specialized perinatal clinics for mood disorders. Depending on the instrument used, 12-30% of these women have symptoms of hypomania or mania after childbirth. The methodological limitations of current studies do not permit any definitive conclusions about the nosology of the highs. The discrepancy between the reported prevalence of the highs in non-clinical populations and the prevalence rates of bipolar disorder in the general population implies that the highs may be analogous to the baby blues in some women. Longitudinal studies are needed to investigate whether the highs are limited to the postpartum period or whether there are some women who continue to have recurrences of the highs outside of the postpartum period.