There is virtually nothing from the irst edition of Williams' 1903 textbook that addresses the common anemias of pregnancy. Only pernicious anemia is devoted two paragraphs to say it occasionally appeared in pregnancy. Today, it is well known that pregnant women are susceptible to hematological abnormalities that may afect any woman of childbearing age. hese include chronic disorders such as hereditary anemias, immunological thrombocytopenia, and malignancies such as leukemias and lymphomas. Other disorders arise during pregnancy because of pregnancy-induced demands. Two examples are iron deiciency and megaloblastic anemias. Pregnancy may also unmask underlying hematological disorders. Finally, any hematological disease may irst arise during pregnancy. Importantly, pregnancy induces physiological changes that often confuse the diagnosis of these hematological disorders and assessment of their treatment (Chap. 4, p. 57).
Normal values for concentrations of many cellular elements during pregnancy are listed in the Appendix (p. 1255). The Centers for Disease Control and Prevention (1998) deined anemia in iron-supplemented pregnant women using a cutof of the 5th percentile-lrl g/dL in the irst and third trimesters, and 10.5 g/dL in the second trimester (Fig.
he modest fall in hemoglobin levels and hematocrit values during pregnancy is caused by a relatively greater expansion of plasma volume compared with the increase in red cell volume. he disproportion between the rates at which plasma and erythrocytes are added to the maternal circulation is greatest during the second trimester. Late in pregnancy, plasma expansion essentially ceases, while hemoglobin mass continues to accrue.
he causes of more common anemias encountered in pregnancy are listed in Table 56-1r. Their frequency is dependent on multiple factors such as geography, ethniciry, socioeconomic level, nutrition, preexisting iron status, and prenatal iron supplementation (American College of Obstetricians and Gynecologists, 2017 a). In the United States, the prevalence of anemia in pregnancy is 3 to 38 percent (Centers for Disease Control and Prevention, 1989). In Latin America and the Caribbean, anemia prevalence ranges from 5 to 45 percent among women of :J taking iron supplements. (Data from the Centers for Disease
Control and Prevention, 1989.) childbearing age (1ujica-Coopman, 2015). Rates are also high in Israel, China, India, South Asia, and Africa (Azulay, 2015; Kumar, 2013, Stevens, 2013). Figure 56-2 highlights the global trends in hemoglobin concentrations and anemia thresholds in pregnant and nonpregnant women.
Most studies of anemia during pregnancy describe large populations and deal with nutritional anemias. Anemia is associated with several adverse pregnancy outcomes including preterm birth (Kidanto, 2009; Kumar, 2013; Rukuni, 2016). Children born to iron-deicient women and without iron supplementation are reported to have lower mental development scores (Drassinower, 2016; Tran, 2014).
A seemingly paradoxical inding is that healthy pregnant women with a higher hemoglobin concentration are also at greater risk for adverse perinatal outcomes (Murphy, 1986; von Tempelhof, 2008). This may result from lower than average plasma volume expansion of pregnancy concurrent with normal red cell mass accrual. Scanlon and associates (2000) studied the relationship between maternal hemoglobin levels and rates of preterm or growth-restricted newborns in 173,031 pregnancies.
TABLE 56-1. Causes of Anemia During Pregnancy