ERYTHROPOIESIS IN PREGNANCY

There is a dramatic increase in total blood volume during healthy pregnancy. The disproportionate expansion in plasma volume (50%) and red cell mass (18-25% depending on iron status) results in a decrease in haemoglobin concentration maximal at 32 weeks gestation. This should not fall below 11 g/dl at any time during pregnancy. Deficiency of essential haematinics arising from increased requirements and inadequate intake may have far reaching effects on mother, fetus and neonate which bear no relationship to the impaired oxygen carrying capacity of the reduced cell mass. Pathological anaemia of pregnancy is due in over 90% of cases to iron deficiency associated with depleted stores and deficient intake. The single largest demand for iron arises from the increased red cell mass under the influence of erythropoietin. Tissue enzyme malfunction occurs even in the very first stages of iron deficiency before significant anaemia develops. Increased blood loss at delivery and preterm birth are observed associated complications. Off-spring of iron deficient mothers have decreased iron stores and may develop anaemia in the first year of life. Studies have shown behavioural abnormalities in children with iron deficiency and poor performance in the Bayley Mental Developmental Index. The poor performance in mental and motor development can be improved to the level of iron-sufficient infants by treatment with ferrous sulphate. Folate deficiency often accompanies iron deficiency as they are both associated with a poor diet. The haematological effects of folate deficiency are usually masked by iron deficiency. Folate deficiency in the mother can lead to megaloblastic changes in her tissues, megaloblastic anaemia in her offspring and particularly in the preterm neonate. The association of periconceptional maternal folate deficiency with neural tube defects has now been established both with the recurrence and with the first occurrence of this devastating abnormality. The Public Health measures to be taken to ensure that the diet of women in reproductive years contains adequate folic acid will need careful prospective planning. Vitamin B-12 deficiency hardly ever causes anaemia in pregnancy. Addisonian pernicious anaemia does not usually occur in the reproductive years and is associated with infertility. Only vegans, who will eat no animal protein whatsoever, may have a vitamin B-12 deficient diet. Anaemia of pregnancy due to deficiency of haematinics should not occur with appropriate prophylaxis. Prevention of deficiency during the reproductive years is important for the health of mother, fetus and infant and will have long-term benefits.