This study determined factors of preterm delivery in Taiwan. Healthy women (n=520, age 29.1±4.2 y) at 8-12 weeks of pregnancy were recruited from prenatal clinics. Background information, anthropometrics, biochemical parameters, and dietary intake, collected by 24 h-recall were obtained from the first, second, and third trimesters to delivery. Clinical outcomes of neonates were also collected. The results show that 53.7% of women were primiparous and that the incidence of preterm delivery was 6.2%. Body weight gains in the first trimester and throughout pregnancy were significantly lower in mothers with preterm delivery (preterm group) than in mothers with term delivery (term group, p<0.05). Maternal cholesterol intake, circulating white blood cell counts (WBC) and serum albumin were significantly lower and that serum magnesium and ferritin were significantly higher in the preterm group than in the term group. Maternal weight gain was positively correlated with caloric and nutrient intake (p<0.05). Neonatal birth weight was positively correlated with maternal weight gain and intakes of protein and phosphate during pregnancy; with intakes of calories, vitamin B-1 and B-2 in the first trimester; and with intakes of calcium, magnesium, iron and zinc, as well as circulating WBC in the third trimester. However, neonatal birth weight was negatively correlated with serum iron in the third trimester and with serum iron and ferritin at the time of delivery. In conclusion, maternal weight gain in early pregnancy and WBC, mineral intake and iron status in late pregnancy seem to be major factors affecting delivery and neonatal outcomes.