The relationship between maternal folic acid supplementation in pregnancy and infant birthweight has not been well described in low-and middle-income countries. We conducted a systematic review and meta-analysis of the current evidence of the association between folic acid supplementation in pregnancy on three primary outcomes: the incidence of low birthweight, small for gestational age, and mean birthweight. Seventeen studies were identified, which satisfied the inclusion criteria, covering a total of 275,421 women from 13 cohort studies and four randomized controlled trials. For the primary outcome of mean birthweight (n = 9), the pooled mean difference between folic acid and control groups was 0.37 kg (95% confidence interval [CI]: 0.24 to 0.50), and this effect was larger in the randomized controlled trials (0.56, 95% CI: 0.15 to 0.97, n = 3). The pooled odds ratio was 0.59 for low birthweight (95% CI: 0.47 to 0.74, n = 10) among folic acid supplementation versus control. The pooled odds ratio for the association with small for gestational age was 0.63 (95% CI: 0.39 to 1.01, n = 5).Maternal folic acid supplementation in low-and middle-income countries was associated with an increased mean birthweight of infants and decreases in the incidence of low birthweight and small for gestational age. K E Y W O R D Sbirthweight, developing countries, folic acid, infant, nutritional status, pregnancy, systematic review