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.