- Objective: The present study examines whether there is an association between anemia during the first trimester and the risk to develop preterm delivery (PTD), intrauterine growth restriction, and other obstetrical complications. Methods: The study population included all registered births between 2000 and 2010. Anemia was defined as hemoglobin <10 g/dl. A comparison of obstetrical characteristics and perinatal outcomes was performed between women with and without anemia. Multiple logistic regression models were used to control for confounders. Results: The study population included 33,888 deliveries, of these 5.1% (1718) were with anemia during the first trimester. Women with anemia were significantly older, delivered earlier, and were more likely to be grand multiparous. There were significantly higher rates of PTD and low birth weight (LBW; <2500 g) among patients with anemia (12.3% vs. 9.3%; p < 0.001 and 11.7% vs. 9.0%; p < 0.001, respectively). On the contrary, no significant differences between the groups were noted regarding the rate of intrauterine growth restriction. Using a multivariable analysis, the significant association between anemia and PTD persisted (OR = 1.35; 95% CI 1.2-1.6, p < 0.01). Conclusions: Anemia during the first trimester is significantly and independently associated with an increased risk for subsequent PTD.