Background: Corn Soya Blend (CSB) Plus is a fortified dietary supplement used to help Cambodian women meet their nutritional requirements in pregnancy, although little is known about its ability to improve pregnancy outcomes.

Objective: This study assessed the effect of prenatal CSB Plus supplementation on birth weight and secondary outcomes of low birth weight (<2500 g), small for gestational age, birth length and head circumference, preterm birth (<37 wk), maternal weight gain, and anemia at 24–28 wk, 30–32 wk, and 36–38 wk of gestation among rural Cambodian women.

Design: A cluster-randomized trial was conducted in 75 villages in Kampong Chhnang Province, in which 547 women received CSB Plus (treatment) during the first trimester until delivery or continued their normal diet (control) based on their village residence. All women received routine daily iron folic acid tablets and were treated with additional iron folic acid if they were anemic (hemoglobin <11 g/dL). Cluster-adjusted linear mixed-effect and logistic regression models were used to examine group differences.

Results: There was no significant difference in birth weight between the CSB Plus and control group (46 g; 95% CI: −31, 123 g; P = 0.24). Significant reductions were observed in preterm birth (OR = 0.33; 95% CI: 0.12, 0.89) and anemia at 36–38 wk (OR = 0.51; 95% CI: 0.34, 0.77). There were no significant differences in low birth weight, small for gestational age, birth length, head circumference, or maternal weight gain. A higher rate of fetal loss was observed in the treatment group (10.2% compared with 3.7%; P < 0.01).

Conclusions: In Cambodian women, CSB Plus consumed during pregnancy did not significantly increase maternal weight gain or improve birth size but did reduce maternal anemia in late gestation and preterm birth in comparison with women consuming a normal diet. The unexpectedly higher rate of fetal loss in the treatment group is concerning and warrants further investigation. This trial was registered at clinicaltrials.gov as NCT01413776.