OBJECTIVE: To review the evidence about the prevalence and determinants of non-psychotic common perinatal mental disorders (CPMDs) in World Bank categorized low- and lower-middle-income countries. METHODS: Major databases were searched systematically for English-language publications on the prevalence of non-psychotic CPMDs and on their risk factors and determinants. All study designs were included. FINDINGS: Thirteen papers covering 17 low- and lower-middle-income countries provided findings for pregnant women, and 34, for women who had just given birth. Data on disorders in the antenatal period were available for 9 (8%) countries, and on disorders in the postnatal period, for 17 (15%). Weighted mean prevalence was 15.6% (95% confidence interval, CI: 15.4-15.9) antenatally and 19.8% (19.5-20.0) postnatally. Risk factors were: socioeconomic disadvantage (odds ratio [OR] range: 2.1-13.2); unintended pregnancy (1.6-8.8); being younger (2.1-5.4); being unmarried (3.4-5.8); lacking intimate partner empathy and support (2.0-9.4); having hostile in-laws (2.1-4.4); experiencing intimate partner violence (2.11-6.75); having insufficient emotional and practical support (2.8-6.1); in some settings, giving birth to a female (1.8-2.6), and having a history of mental health problems (5.1-5.6). Protective factors were: having more education (relative risk: 0.5; P = 0.03); having a permanent job (OR: 0.64; 95% CI: 0.4-1.0); being of the ethnic majority (OR: 0.2; 95% CI: 0.1-0.8) and having a kind, trustworthy intimate partner (OR: 0.52; 95% CI: 0.3-0.9). CONCLUSION: CPMDs are more prevalent in low- and lower-middle-income countries, particularly among poorer women with gender-based risks or a psychiatric history.