Anemia in Pregnancy

This one pairs nicely with the 2020 Bonterra Cabernet Sauvignon (Organic)

Five Pearls

1. Normal physiologic changes in pregnancy that are relevant in anemia: blood volume expands by 50% (increased iron requirement), red blood cell mass increases by 25% in a singleton pregnancy, and increased iron stores in the female body during pregnancy help to sustain the increased demand.

2. Low serum ferritin is the most sensitive and specific single lab finding in iron deficiency anemia. And yet, it’s specificity isn’t great.

3. The CDC recommends universal screening for iron deficiency anemia in pregnancy along with universal supplementation.

4. B12 deficiency and folate deficiency are common causes of macrocytic anemia; folate deficiency much more likely than B12.

5. Blood transfusions are almost never indicated in pregnancy, apart from the rare case of a large, concealed placental abruption (Hgb <6 g/dL is associated with abnormal fetal oxygenation --> non-reassuring fetal heart rate patterns, reduced amniotic fluid volume, fetal cerebral vasodilation, and fetal death)

Definition of anemia in pregnancy

Hgb = hemoglobin; HCT = hematocrit

- Hgb <11g/dL or HCT <33% in the first/third trimesters

- <10.5 g/dL or <32% in the second trimester

- everybody should be screened in the 1st trimester and at 24-28 weeks

- If hematocrit level is less than 33% in the first and third trimesters or less than 32% in the second trimester, you need to investigate the cause. If iron deficiency is ruled out, other etiologies should be investigated

- Living at a high altitude and tobacco use cause a generalized increase in hematocrit and hemoglobin levels, and consideration of these factors may be appropriate when interpreting test results

Classification of anemia

Physiologic changes in pregnancy that may lead to anemia

- blood volume expands by 40-50% (increased iron requirement)

- red blood cell mass increases by 15-25% in a singleton pregnancy

- increased iron stores in the female body during pregnancy help to sustain the increased demand

**UK guidelines on iron deficiency anemia: https://www.bsg.org.uk/wp-content/uploads/2021/09/Iron-Deficiency-Anaemia-in-Adults.pdf

“An SF level of <15 µg/L is indicative of absent iron stores, while SF levels of less than 30 µg/L are generally indicative of low body iron stores. The lower limit of normal for most laboratories, therefore, lies in the range 15–30 µg/L.”

Structure of hemoglobin

- four polypeptide chains + heme

- the six chain types: alpha (α), beta (β), gamma (γ), delta (δ), epsilon (ε), and zeta (ζ)

- adult hemoglobin consists of two alpha chains + either two β-chains (hemoglobin A), two γ-drains (hemoglobin F), or two δ-chains (hemoglobin A₂)

- hemoglobin F predominates in the developing fetus from 12 -24 wga, after which hemoglobin A begins to increase

Iron deficiency anemia

- 2% prevalence in general female population (2x higher for black women compared to white)

- “An assessment of iron status in pregnant individuals in the United States using data from the National Health and Nutrition Examination Survey (known as NHANES) from 1999 to 2006 found that iron deficiency prevalence increased significantly with each trimester (mean ± standard error, 7%, 14%, and 30%, in the first, second, and third trimesters, respectively) and was higher in Mexican American pregnant women, non-Hispanic Black pregnant women, and women with parity greater than 2”

- in pregnancy, higher prevalence by far in 3rd trimester

- associated with low birth weight, preterm delivery, and perinata