Aim: Preterm birth and low birthweight (LBW) lead to infant morbidity and mortality. The causes are unknown. This study evaluates the association between duration of maternity leave and birth outcomes at country level. Method: We compiled data on duration of maternity leave for 180 countries of which 36 specified prenatal leave, 190 specified income, 183 specified preterm birth rates and 185 specified the LBW rate. Multivariate and seemingly unrelated regression analyses were done in STATA. Results: Mean maternity leave duration was 15.4 weeks ( SD=7.7; range 4–52 weeks). One additional week of maternity leave was associated with a 0.09% lower preterm rate (95% confidence interval [CI] –0.15 to −0.04) adjusting for income and being an African country. An additional week of maternity leave was associated with a 0.14% lower rate of LBW (95% CI –0.24 to −0.05). Mean prenatal maternity leave across 36 countries was six weeks ( SD=2.7; range 2–14 weeks). One week of prenatal maternity leave was associated with a 0.07% lower preterm rate (95% CI –0.10 to 0.24) and a 0.06% lower rate of LBW (95% CI –0.14 to 0.27), but these results were not statistically significant. By adjusting for income status categories, the preterm birth rate was 1.53% higher and the LBW rate was 2.17% higher in Africa compared to the rest of the world. Conclusions: Maternity leave duration is significantly associated with birth outcomes. However, the association was not significant among 36 countries that specified prenatal maternity leave. Studies are needed to evaluate the correlation between prenatal leave and birth outcomes.