Hemoglobin and hematocrit measurements are performed in almost all women admitted to a hospital in labor. Sherard and Newton questioned the need for this testing if screening for anemia during pregnancy is normal. They argued that the physiologic changes of pregnancy result in the lowest hemoglobin and hematocrit values at 26 to 28 weeks of gestation. Around this time, testing for anemia is usually conveniently performed when blood is drawn for hyperglycemia screening. In their study, they evaluated the ability of hemoglobin and hematocrit measurements at 26 to 28 weeks of gestation to predict values during labor.

The study included 101 consecutive women admitted in labor at term to a hospital labor and delivery unit. In these women, hemoglobin and hematocrit measurements were obtained on admission and at 26 to 28 weeks of gestation. Women with preterm delivery and pregnancies complicated by hemoglobinopathies, hypertension, or multiple gestation were excluded. In addition to gathering data on the pregnant women, the authors interviewed 31 obstetric specialists from the unit to identify the hemoglobin and hematocrit values at which patient management decisions would be affected.

The average age of the women was 24 years, and 64 percent were multigravidas. The racial demographics were 40 percent black, 30 percent white, and 30 percent Hispanic. Approximately two thirds of the women were Medicaid recipients. Prenatal care was provided by the university clinic for 75 percent of the women, and the remainder received care at local health departments. All of the women were provided with prenatal vitamins; the university clinic vitamins contained 65 mg of iron and 1.0 mg of folate. More than 80 percent of the women reported taking the vitamins. The 20 mothers who had hemoglobin levels below 10 g per dL (100 g per L) or a hematocrit level below 30 percent (0.30) at 26 to 28 weeks of gestation were provided with 325 mg per day of ferrous sulfate. Fewer than one half of the women reported taking the supplement.

By the time the women were admitted in labor, the mean hemoglobin and hematocrit values had increased by a mean of 0.5 g per dL (5 g per L) and 2.8 percent (0.03), respectively. Only four of the 20 women who were anemic at 26 to 28 weeks of gestation were still anemic at term. More than 80 percent of the women who were anemic at 26 to 28 weeks of gestation were no longer anemic on admission at term, in spite of the low compliance with therapy. Management plans were not changed in any patient because of concerns about mild anemia.

The authors concluded that the screening performed at 26 to 28 weeks of gestation occurs at the physiologic nadir of blood values in pregnancy. If hemoglobin and hematocrit values are acceptable at that time, retesting later in pregnancy is not necessary in low-risk pregnant women. The potential savings would be between $22 and $39 per patient, depending on whether hemoglobin and hematocrit measurements or a complete blood count is ordered. If applied nationally, the savings would amount to $100 million per year.