BACKGROUND: Low birth weight (LBW), anaemia and malaria are common in Papua New Guinean (PNG) women. METHODS: To identify risk factors for LBW, anaemia and preterm delivery (PTD), pregnant women recruited into a cohort study in Madang, PNG were followed to delivery. RESULTS: Of 470 women enrolled, delivery data were available for 328 (69.7 ). By microscopy, 34.4 (113/328) of women had malaria parasitaemia at enrolment and 12.5 (41/328) at delivery; at each time point, PCR detected sub-microscopic parasitaemia in substantially more. Most infections were with Plasmodium falciparum; the remainder being predominantly P. vivax. Anaemia and smoking were associated with lower birth weight, and LBW (16.7 ; 51/305) and PTD (21.8 ; 63/290) were common. Histopathologically-diagnosed chronic placental malaria was associated with LBW (adjusted odds ratio [aOR] 3.3; p=0.048) and PTD (aOR 4.2; p=0.01). Lack of maternal education predisposed to PTD. Sub-microscopic parasitaemia at delivery appeared to increase risk of LBW. Of the genetic polymorphisms Southeast Asian ovalocytosis, alpha+-thalassaemia and complement receptor 1 (CR1) deficiency, a CR1 heterozygous genotype was associated with decreased risk of anaemia, and substantial, but non-significant, effects were noted in other comparisons. CONCLUSIONS: In coastal PNG, malaria and anaemia are important causes of adverse pregnancy outcomes.