Redefining normal hemoglobin and anemia in singleton and twin pregnancies

To assess the benefit of a hemoglobin cutoff of 105 g/L as a trigger for anemia evaluation during the second trimester of pregnancy.

The present cross-sectional study, conducted at a health center in Israel between January 1, 2010, and December 31, 2015, included pregnant women with hemoglobin values below 105 g/L who were assessed for anemia. Anemia workup included complete blood count, serum ferritin and vitamin B12 measurements, and hemoglobin electrophoresis. The primary outcome was the incidence of nondilutional anemia, defined by a positive workup, across predefined hemoglobin thresholds. Receiver operating characteristic curves were created to identify the best hemoglobin threshold for predicting anemia, mandating further evaluation.

In total, 651 women with singleton and 300 women with twin pregnancies were evaluated for nondilutional anemia. Of these, 340 (52.2%) and 127 (42.3%) women, respectively, had positive workup results. The most common cause was iron deficiency. The hemoglobin values that best predicted positive workup results were 100 g/L in singleton pregnancies and 97 g/L in twin pregnancies.

Anemia evaluation could be unnecessary in pregnant women with a hemoglobin value of 100-105 g/L. Consideration should be given to redefining anemia in singleton and twin pregnancies.