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Keywords:

  • erythrocyte indices;
  • hemoglobin;
  • iron metabolism;
  • iron status;
  • iron supplementation;
  • postpartum;
  • pregnancy;
  • reference interval

Background. The aim was to define reference values for hemoglobin, hematocrit and erythrocyte indices, i.e. erythrocyte count, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), in normal pregnancy and after a normal delivery in non-iron-supplemented and iron supplemented women.

Methods. Two hundred and six healthy Danish women included at 9–18 weeks of gestation were allocated to treatment with placebo tablets (n=107) or tablets containing 66 mg iron (n=99). Blood samples were obtained at inclusion, every fourth week during gestation, and 8 weeks postpartum.

Results. All hematologic indices were significantly lower in placebo-treated than in iron-treated women. In placebo-treated women, the 5th percentile for hemoglobin was 110 g/L in the 1st trimester; in the 2nd trimester it was 105 g/L in the first and the second, and 103 g/L in the last third; in the 3rd trimester, it was 102 g/L in the first, 100 g/L in the second, and 101 g/L in the last third; postpartum it was 113 g/L. In iron-treated women, the 5th percentile for hemoglobin was 111 g/L in the 1st trimester; in the 2nd trimester it was 109 g/L in the first, 106 g/L in the second, and 103 g/L in the last third; in the 3rd trimester, it was 105 g/L in the first and second, and 110 g/L in the last third; postpartum it was 123 g/L.

Conclusions. Hematologic reference values should be derived from iron replete women.We suggest that the lowest critical hemoglobin value in iron-treated pregnant women should be 110 g/l (6.8 mmol/L) in the 1st trimester, and 105 g/L (6.5 mmol/L) in the 2nd and 3rd trimester.