The nutritional status of a woman before and during pregnancy is important for a healthy pregnancy outcome. Maternal malnutrition is a key contributor to poor fetal growth, low birthweight (LBW) and short- and long-term infant morbidity and mortality. This review summarised the evidence on association of maternal nutrition with birth outcomes along with review of effects of balanced protein-energy supplementation during pregnancy. A literature search was conducted on PubMed, WHOLIS, PAHO and Cochrane library. Only intervention studies were considered for inclusion and data were combined by meta-analyses if available from more than one study. Sixteen intervention studies were included in the review. Pooled analysis showed a positive impact of balanced protein-energy supplementation on birthweight compared with control [mean difference 73 (g) [95% confidence interval (CI) 30, 117]]. This effect was more pronounced in undernourished women compared with adequately nourished women. Combined data from five studies showed a reduction of 32% in the risk of LBW in the intervention group compared with control [relative risk (RR) 0.68 [95% CI 0.51, 0.92]]. There was a reduction of 34% in the risk of small-for-gestational-age babies in the intervention compared with the control group [RR 0.66 [95% CI 0.49, 0.89]]. The risk of stillbirth was also reduced by 38% in the intervention group compared with control [RR 0.62 [95% CI 0.40, 0.98]]. In conclusion, balanced protein-energy supplementation is an effective intervention to reduce the prevalence of LBW and small-for-gestational-age births, especially in undernourished women.