From the Guidelines
Anemia in pregnancy is defined as a hemoglobin level below 11 g/dL in the first and third trimesters, or below 10.5 g/dL in the second trimester. This definition is based on the most recent and highest quality study available, which prioritizes morbidity, mortality, and quality of life as the outcome 1. The condition affects approximately 40% of pregnant women worldwide and is primarily caused by iron deficiency, though folate and vitamin B12 deficiencies can also contribute. During pregnancy, blood volume increases by about 50% while red blood cell mass increases by only 20-30%, causing a physiologic hemodilution that can mask true anemia.
Key Points to Consider
- Iron deficiency anemia is treated with oral iron supplements, typically ferrous sulfate 325 mg (containing 65 mg elemental iron) taken once or twice daily between meals with vitamin C to enhance absorption 1.
- Side effects include constipation and nausea, which can be managed by taking iron with food if needed.
- Severe anemia (hemoglobin <7 g/dL) may require intravenous iron therapy.
- Untreated anemia in pregnancy increases risks of preterm birth, low birth weight, postpartum depression, and maternal mortality, making routine screening at the first prenatal visit and again at 24-28 weeks essential for maternal and fetal wellbeing 1.
Importance of Screening and Treatment
The US Preventive Services Task Force recommends screening for iron deficiency anemia in pregnant women to improve maternal health and birth outcomes 1. Treatment of iron deficiency anemia in pregnant women is similar to that in nonpregnant women and includes additional iron intake through oral iron pills, prenatal vitamins, and diet. The usual dose is 60 to 120 mg of elemental iron per day 1. Intravenous iron treatment is also used during pregnancy.
Dietary Iron and Supplementation
According to the Institute of Medicine, the Recommended Dietary Allowance for iron in pregnant women is 27 mg per day 1. Natural food sources of iron include certain fruits, vegetables, meat, and poultry. Prenatal vitamins often include a low dose of iron; the usual dose prescribed in early pregnancy is 30 mg of elemental iron per day. Higher doses (60 to 100 mg of elemental iron per day) are sometimes prescribed in populations at increased risk for iron deficiency anemia 1.
From the Research
Definition of Anemia in Pregnancy
- Anemia is defined as a low red blood cell count, a low hematocrit, or a low hemoglobin concentration 2.
- In pregnancy, a hemoglobin concentration of less than 11.0 g/dL in the first trimester and less than 10.5 or 11.0 g/dL in the second or third trimester is considered anemia 2.
- Any hemoglobin below 10.5 g/dL can be regarded as true anemia regardless of gestational age 3.
Diagnosis and Screening
- The American College of Obstetricians and Gynecologists recommends screening for anemia with a complete blood count in the first trimester and again at 24 0/7 to 28 6/7 weeks of gestation 2.
- Testing for iron deficiency is indicated for patients with anemia and/or symptoms of iron deficiency, and should be considered for those with risk factors such as heavy menstrual bleeding, pregnancy, or inflammatory bowel disease 4.
- Iron deficiency is diagnosed by low serum ferritin or transferrin saturation less than 20% 4.
Causes and Risks
- The most common causes of anemia in pregnancy are iron deficiency and acute blood loss 5.
- Iron deficiency is the most common cause of anemia in pregnancy, with a worldwide prevalence between estimated 20%-80% 3.
- Anemia in pregnancy is associated with adverse fetal, neonatal, and childhood outcomes, and increases the likelihood of transfusion at delivery 2.
- Pregnancy anemia can be aggravated by various conditions such as uterine or placental bleedings, gastrointestinal bleedings, and peripartum blood loss 3.
Prediction and Prevention
- First trimester hemoglobin levels can be used to predict anemia during the third trimester, with a cut-off of 12.6 g/dL yielding a sensitivity of 83% 6.
- Prophylaxis of iron deficiency is important to prevent anemia in pregnancy, and oral iron is typically first-line therapy for iron deficiency anemia 3, 4.