Abstract: Objective To explore the relationship between pre-pregnancy body mass index (BMI), gestational weight gain and infants hemoglobin. Methods Mothers and infants who had regular physical examination were selected. General condition of mother and childbirth were collected by questionnaire. The statistical analysis was performed by univariate analysis and multivariate logistic regression model. Results Of all 980 subjects, 19.0% women were underweight, 71.0% with normal BMI, and 10.0% were classified as overweight or obesity according to their pre-pregnancy BMI. As the United States IOM standard, 27.8% women was less than the recommended value, while 31.4% were within it, but 40.8% exceeded institute of medicine (IOM) standard. The incidence of anemia was 49.7%. Univariate analysis showed that pre-pregnancy BMI and weight gain during pregnancy were statistically significant for anemia (all P<0.05). Multivariate analysis showed that pre-pregnancy emaciation (OR=2.027, 95% CI:1.433-2.867), insufficient gestational weight gain (OR=2.499, 95% CI:1.772-3.523) were risk factors for anemia in infants. Conclusions The pre-pregnancy BMI and gestational weight gain may be risk factors for infant anemia. Therefore, control of pre-pregnancy BMI and weight gain during pregnancy can effectively reduce risk of anemia.