Can anemia in the first trimester predict obstetrical complications later in pregnancy?

It is well known that anemia is a major risk factor with respect to fetal and maternal perinatal morbidity and mortality. However, in many studies, interpretation of the data is difficult because of the heterogenety of populations and confounding factors such as lack of clear definitions for anemia and lack of information concerning time of onset of anemia during pregnancy. The study of Tzur et al. has the merit of presenting a clear definition of the time and onset of anemia during pregnancy in their study population, namely the first trimester. Furthermore, anemia is clearly defined as a hemoglobin of less than 10 g/dL. A large number of women was analyzed retrospectively (33,188 women). A prevalence of 5.1% of anemic women was found. Had CDC criteria been used, whereby a hemoglobin below 11 g/dL is defined as anemia during the first trimester, the prevalence would have been even higher.

The authors show a clear relationship between anemia during the first trimester and preterm birth with an odds ratio of 1.35 for a preterm birth below 37 and 34 weeks. In addition, women with first-trimester anemia have a nearly twofold risk for postpartum hemorrhage and a fourfold risk for blood transfusion. These are clear and compelling arguments for the early assessment and treatment of anemia as early as possible before pregnancy or, if possible, in early pregnancy in view of preventing complications. Considering a 5% rate of preterm birth in most populations of the Western world and its impact on the medical and socioeconomic burden, it is easy to estimate the benefits of avoiding anemia in the pregnant patient as one of the major risk factors for preterm birth.

The authors do not describe the underlying causes of anemia in their group of patients but state that iron deficiency could be the main reason for anemia in most patients. Therefore, the second important message is that iron status should be assessed early in pregnancy and iron deficiency should be prevented or treated as early as possible to prevent anemia later in pregnancy.

– Christian Breymann