Types of anemia in pregnancy
Iron deficiency anemia in pregnancy
Worldwide the contribution of Anemia in pregnancy to maternal and fetal morbidity and mortality is well recognized; in some parts of Africa, more than 75 percent of pregnant women are anemic, and there is a significant correlation between maternal mortality and anemia. Iron deficiency may protect against placental malaria, but epidemiologic studies have not been conducted to verify this supposition. In pregnant women, anemia is defined as a hemoglobin concentration of less than 11 g/dL in the first and third trimesters, and less than 10.5 g/dL in the second trimester.
In both the industrialized and the developing world, iron deficiency anemia is the commonest cause of anemia. On average approximately 1 g of iron is required during a normal pregnancy; 300 mg of iron are required by the fetus and the placenta, whereas expansion of the maternal red blood cell mass requires 500 mg, and 200 mg are lost via excretion. These requirements exceed the iron storage of most young women and in general cannot be met by the diet. Even in cases of maternal iron deficiency, the fetal requirements for iron are always met; thus there is no correlation between the hemoglobin of the fetus and that of the mother.
Iron deficiency anemia during the first two trimesters of pregnancy is associated with a two fold increased risk for preterm delivery and a three fold increased risk for delivery of a low birth weight infant. However, a large randomized trial comparing routine iron prophylaxis in pregnancy versus iron supplementation given only as needed demonstrated no significant differences in adverse maternal or fetal outcomes. As in non pregnant individuals, iron deficiency anemia can generally be diagnosed using laboratory values such as serum ferritin, and transferrin saturation levels. Pica, the ingestion of non nutritive substances, is said to be more common among iron deficient pregnant women than among other populations with iron deficiency. Ice, clay or dirt, and starch are the most frequent substances ingested to some extent, however, the choice appears to be cultural and much more wide spread than most practitioners’ realize.
Folate and Vitamin B12 Deficiency Anemia in Pregnancy
Apart from iron deficiency, folate deficiency is the next most frequent nutritional deficiency leading to anemia in pregnant women. In the United States, where food stuffs are supplemented with folate and the level of awareness of the association between folate deficiency and neural tube defects in the embryo is high, folate deficiency is relatively unusual.
Folate requirements in pregnancy are roughly twice those in the non pregnant state (800 mcg/day vs. 400 mcg/day), and if diet is insufficient may exceed the body’s stores of folate (5–10 mg) relatively quickly. Anemia related to folate deficiency most often presents in the third trimester and responds to folate supplementation with reticulocytosis within 24 to 72 hours.
Reports of severe pancytopenia and even states resembling the HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome as a result of folate deficiency in pregnancy have appeared in the literature. Despite these case reports, a review of 21 trials measuring the effect of folate supplementation on biochemical and hematologic parameter sand pregnancy outcome (excluding neural tube defects) revealed improvement in low hemoglobin level in late pregnancy, but had no measurable effect on any substantive measures of pregnancy outcome.
Vitamin B12 deficiency Anemia in pregnancy is rare, in part because deficiency of this vitamin leads to infertility. Serum cobalamin levels are known to fall during pregnancy. A shift from the serum to tissue stores is proposed to account for the drop in serum B12 levels. However, values less than 180 pmol/L usually are not observed in healthy women, and these low normal levels are not accompanied by increased levels of methylmalonic acid, an indicator of cellular deficiency.
Red cell aplasia
A rare cause of Anemia in pregnancy is pure red cell aplasia . In pure red cell aplasia, anemia tends to occur early in pregnancy and often resolves within weeks of delivery.
The pathogenic mechanism leading to red cell aplasia Anemia in pregnancy does not appear to be transferred to the fetus, but does tend to recur in subsequent pregnancies.
Conservative treatment, if feasible, is probably best until delivery; successful prenatal treatments with glucocorticoids and with intravenous immunoglobulin have been reported.