Obgyno Wino Podcast Episode 63 - Anemia in Pregnancy
“Sometimes the one who is running from the Life/Death/Life nature insists on thinking of love as a boon only. Yet love in its fullest form is a series of deaths and rebirths. We let go of one phase, one aspect of love, and enter another. Passion dies and is brought back. Pain is chased away and surfaces another time. To love means to embrace and at the same time to withstand many endings, and many many beginnings - all in the same relationship.”
- Clarissa Pinkola Estés
PB#95 - Published July 2008 (Reaffirmed 2017)
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.
3. The CDC recommends universal screening for iron deficiency anemia in pregnancy along with universal supplementation.
4. B12 deficiency and folic acid deficiency are common causes of macrocytic anemia; folic acid 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
Classification of anemia
Physiologic changes in pregnancy that may lead to anemia
- blood volume expands by 50% (increased iron requirement)
- red blood cell mass increases by 25% in a singleton pregnancy
- increased iron stores in the female body during pregnancy help to sustain the increased demand
Iron deficiency anemia
- 2% prevalence in general female population (2x higher for black women compared to white)
- in pregnancy, higher prevalence by far in 3rd trimester
- associated with low birth weight, preterm delivery, and perinatal mortality
- diagnosed by lab analysis OR if there's an increase in Hgb by 1g/dL after iron treatment OR by the absence of bone marrow iron stores on bone marrow biopsies
- iron storage may be low (iron depletion), or stored + transport iron are low (decreased erythropoiesis), or stored + transport + functional iron are all low (full blown iron deficiency anemia, yeehaw!)
- on iron studies, iron deficiency anemia presents as: microcytic, hypochromic, iron store depletion, low plasma iron, increased total iron-binding capacity (TIBC), low serum ferritin, and increased free erythrocyte protoporphyrin
- serum ferritin levels are most specific and sensitive for the diagnosis (<10-15 mcg/L is diagnostic)
- CDC recommends universal screening of pregnant women along with universal supplementation (unless the patient has hemochromatosis)
- typical American diet provide 15 mg of elemental iron per day (recommended: 27 mg daily iron intake)
- extended-release formulations are less effective
- foods rich in iron: shellfish, beef, organ meats, turkey, beans, and lentils
- foods that enhance iron absorption from the gut: citrus, strawberries, broccoli, and peppers
- foods that impair iron absorption: dairy, soy, spinach, and coffee
- two general categories: megaloblastic (B12 or folic acid deficiency, pernicious anemia) and non-megaloblastic (liver disease, myelodysplasia, increased reticulocytes, aplastic anemia, and hypothyroidism)
- mean corpusucular volume (MCV) >100 fL is characteristic of macrocytic anemia
- if >115 fL, diagnostic for folic acid or B12 deficiency (confirm by checking serum folic acid or B12 levels)
- in the U.S., macrocytic anemia in pregnancy is due almost exclusively to folic acid deficiency
- recall: folic acid should universally be supplemented at 400 mcg per day in pregnancy
- folic acid deficiency can be caused by diets deficient in leafy vegetables, legumes, or animal proteins (or taking antacids) - changing the diet should do the trick (you can also increased folic acid supplementation to 1 mg daily along with increasing iron supplementation)
- B12 deficiency can be seen in women who have undergone partial or total gastric resection or in Crohn disease
- treatment includes supplementing with 1000 mcg of B12 (intramuscular) monthly
What if a patient has laboratory evidence of anemia but is asymptomatic?
- mild: reasonable to investigate further through iron studies, RBC indices, etc. (otherwise you may just recommended dietary changes without investigation)
- moderate: definitely investigate the etiology (CBC, RBC indices, iron studies, blood smear), consider Hgb electrophoresis if patient is of African, Southeast Asian, or Mediterranean descent; reasonable to treat empirically with iron while awaiting further studies (you should see results in a few weeks)
When should transfusion be considered?
- almost never 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)
- postpartum is a different story: coagulopathy (HELLP, DIC, etc.), uterine atony, placenta previa/accreta, and placental abruption may all result in the need for transfusion postpartum
- if the patient becomes symptomatic or hemodynamically unstable then it's a no-brainer
When should iron infusion be considered?
- useful for the rare patient who can't tolerate oral iron or those who have severe malabsorption issues
- 1% chance of anaphylaxis (iron dextran more likely to cause a reaction than ferrous sucrose)
- faster immediate results from IV iron compared to oral for most patients, but by day 40 after treatment, the two routes of comparable
- insufficient data to guide decisions around erythropoietin treatment in pregnancy