Objective: To determine the prevalence and causes of anemia during pregnancy in Maharaj Nakorn Chiang Mai Hospital.
Material and Method: The pregnant women were screened with hemoglobin, hematocrit, osmotic fragility test, hemoglobin E test and serology for hepatitis B, syphilis and HIV at first antenatal visit. In anemic cases, serum ferritin, serum iron/total iron binding capacity, or therapeutic trial with iron supplementation were performed to assess the iron status. The cases of abnormal thalassemia screening were followed by hemoglobin A2 level, PCR for alpha-1(SEA type) and hemoglobin electrophoresis. Additional tests were stool exam, stool occult blood and red blood cell indices. Anemia was defined as a hemoglobin level less than 11.0 g/dl in the first and third trimester or less than 10.5 g/dl in the second trimester of pregnancy. The data was presented as mean, standard deviation and percentage.
Results: Six hundred and forty eight pregnant women were recruited. The prevalence of anemia was 20.1 percent(128 cases). Classified in each trimester, the prevalence was 17.3%, 23.8% and 50.0% in the first, second and third trimester, respectively. Thalassemia carriers and diseases were detected in 56 from 102 anemic pregnant women (54.9%). Iron status was assessed in 58 cases and iron deficiency anemia was found in 25 cases (43.1%). Other causes of anemia were parasitic infection (8.7%) and anemia of chronic disease (2.7%). In 37 anemic pregnant women (33.0%), the causes of anemia were not found.
Conclusion: The prevalence of anemia in pregnant women who first attended at the antenatal clinic was 20.1%. The main causes of anemia were thalassemia carriers/diseases and iron deficiency anemia.

Keywords: Anemia, Pregnancy, Prevalence, Thalassemia, Iron-deficiency anemia