What are the common causes of low hematocrit during pregnancy. How does anemia affect pregnancy outcomes. What are the diagnostic approaches for anemia in pregnant women. How is anemia treated during pregnancy.

Understanding Hematocrit and Hemoglobin Changes in Pregnancy

During pregnancy, significant changes occur in a woman’s blood composition. While red blood cell (RBC) mass increases due to erythroid hyperplasia of the bone marrow, there’s a disproportionate rise in plasma volume. This phenomenon leads to hemodilution, also known as hydremia of pregnancy.

The effects of hemodilution on hematocrit (Hct) levels are notable:

• Non-pregnant healthy women: Hct between 38% and 45%
• Late single pregnancy: Hct decreases to about 34%
• Late multifetal pregnancy: Hct can drop to 30%

Despite these changes, it’s crucial to understand that the oxygen-carrying capacity remains normal throughout pregnancy. However, certain hemoglobin (Hb) and Hct levels are classified as anemic during different trimesters:

• 1st trimester: Hb < 11 g/dL
• 2nd trimester: Hb < 10.5 g/dL
• 3rd trimester: Hb < 11 g/dL

Prevalence and Common Causes of Anemia in Pregnancy

Anemia affects up to one-third of women during the third trimester of pregnancy. The most frequent causes include:

1. Iron deficiency (accounting for about 95% of anemia cases during pregnancy)
2. Folate deficiency

Iron deficiency anemia often results from:

• Inadequate dietary intake, especially in adolescent girls
• Previous pregnancies
• Normal recurrent loss of iron in menstrual blood before pregnancy

Symptoms and Risks Associated with Anemia in Pregnancy

Early symptoms of anemia during pregnancy can be subtle or nonexistent. When present, they may include:

• Fatigue
• Weakness
• Light-headedness
• Mild dyspnea during exertion

In severe cases, additional symptoms and signs may manifest:

• Pallor
• Tachycardia
• Hypotension

Anemia during pregnancy increases the risk of several complications:

• Preterm delivery
• Low birth weight
• Postpartum maternal infections

Diagnostic Approaches for Anemia in Pregnant Women

The diagnosis of anemia in pregnancy begins with a complete blood count (CBC). Further testing is typically based on the mean corpuscular volume (MCV):

Microcytic Anemia (MCV < 80 fL)

For microcytic anemias, evaluation includes:

• Testing for iron deficiency by measuring serum ferritin
• Screening for hemoglobinopathies using hemoglobin electrophoresis

If these tests are inconclusive and there’s no response to empiric treatment, consultation with a hematologist is usually warranted.

Macrocytic Anemia (MCV > 100 fL)

For macrocytic anemias, evaluation includes:

• Serum folate levels
• Vitamin B12 levels

Mixed Anemia

In cases of anemia with mixed causes, evaluation for both microcytic and macrocytic types is required.

Treatment Strategies for Anemia During Pregnancy

The primary goal of treatment is to reverse the anemia by addressing its underlying cause. However, the approach may vary depending on the severity of symptoms and the specific type of anemia.

Iron Deficiency Anemia Treatment

For iron deficiency anemia, which accounts for the majority of cases, the typical treatment involves iron supplementation:

• One 325-mg ferrous sulfate tablet taken midmorning is usually effective
• Higher or more frequent doses may increase gastrointestinal adverse effects

Severe Anemia and Transfusion

Transfusion is usually indicated for any anemia if severe constitutional symptoms or cardiopulmonary signs are present. The decision to transfuse is not based solely on the hematocrit level but on the overall clinical picture.

Special Considerations: Anemia in Jehovah’s Witness Patients

Obstetricians should evaluate anemia in pregnant Jehovah’s Witness patients as soon as possible, in consultation with a perinatologist. This is particularly important as these patients are likely to refuse blood transfusions, necessitating alternative management strategies.

Prevention and Management of Iron Deficiency in Pregnancy

Given the high prevalence of iron deficiency anemia in pregnancy, preventive measures are crucial. These may include:

• Dietary counseling to increase iron intake
• Routine iron supplementation during pregnancy
• Early screening for anemia, especially in high-risk groups

Proper management of iron deficiency can significantly reduce the risk of complications associated with anemia in pregnancy.

The Role of Folate and Vitamin B12 in Pregnancy

While iron deficiency is the most common cause of anemia in pregnancy, folate and vitamin B12 deficiencies also play important roles. Understanding their significance can help in comprehensive anemia management:

Folate in Pregnancy

Folate is crucial for fetal development, particularly in preventing neural tube defects. Its deficiency can lead to megaloblastic anemia. Key points include:

• Increased folate requirements during pregnancy
• Recommended supplementation before and during early pregnancy
• Dietary sources of folate (leafy greens, legumes, fortified grains)

Vitamin B12 in Pregnancy

Vitamin B12 is essential for proper red blood cell formation and neurological function. Its deficiency can also cause megaloblastic anemia. Important considerations include:

• Increased vitamin B12 needs during pregnancy
• Potential for deficiency, especially in vegetarian or vegan mothers
• Supplementation strategies for at-risk individuals

Do pregnant women need additional folate and vitamin B12 beyond their prenatal vitamins? In most cases, prenatal vitamins provide adequate amounts of these nutrients. However, women with certain risk factors or pre-existing deficiencies may require additional supplementation under medical supervision.

Monitoring and Follow-up for Anemia in Pregnancy

Effective management of anemia in pregnancy requires ongoing monitoring and follow-up. This process typically involves:

1. Regular CBC tests to track hemoglobin and hematocrit levels
2. Assessment of symptoms and overall maternal health
3. Evaluation of fetal growth and well-being
4. Adjustment of treatment plans as needed

How often should pregnant women with anemia have their blood levels checked? The frequency of monitoring depends on the severity of anemia and the treatment response. Typically, follow-up tests are performed every 2-4 weeks, but more frequent monitoring may be necessary in severe cases.

Impact of Anemia on Postpartum Health

The effects of anemia during pregnancy can extend into the postpartum period, influencing maternal recovery and breastfeeding. Key considerations include:

• Increased risk of postpartum hemorrhage
• Potential impact on milk production and quality
• Prolonged fatigue and delayed recovery
• Increased susceptibility to postpartum infections

How long should iron supplementation continue after delivery for women who had anemia during pregnancy? In most cases, iron supplementation should continue for at least 6-12 weeks postpartum, or until hemoglobin levels normalize. However, the exact duration may vary based on individual circumstances and should be determined by a healthcare provider.

Emerging Research and Future Directions

As our understanding of anemia in pregnancy evolves, new research areas and treatment approaches are emerging:

• Novel iron formulations with improved absorption and fewer side effects
• Investigation of the long-term effects of maternal anemia on child development
• Exploration of genetic factors influencing iron metabolism during pregnancy
• Development of more accurate and accessible diagnostic tools for anemia in resource-limited settings

Can advances in genetic testing help identify women at higher risk for anemia during pregnancy? While genetic testing shows promise in identifying certain hereditary forms of anemia, its routine use for predicting anemia risk in pregnancy is still under investigation. Future research may lead to more personalized approaches to anemia prevention and treatment based on genetic profiles.

Global Perspectives on Anemia in Pregnancy

Anemia in pregnancy is a global health concern, with varying prevalence and impact across different regions:

• Higher rates in developing countries due to nutritional deficiencies and infectious diseases
• Challenges in diagnosis and treatment in resource-limited settings
• Cultural and dietary factors influencing anemia risk and management
• International initiatives aimed at reducing the global burden of maternal anemia

How do strategies for managing anemia in pregnancy differ between developed and developing countries? In developed countries, the focus is often on routine screening and supplementation, with easy access to advanced diagnostic tools. In contrast, developing countries may emphasize community-based interventions, fortification of staple foods, and addressing underlying issues like malnutrition and parasitic infections.

Educating Patients about Anemia in Pregnancy

Patient education plays a crucial role in preventing and managing anemia during pregnancy. Key topics to cover include:

1. The importance of a balanced diet rich in iron, folate, and vitamin B12
2. Proper use of prenatal vitamins and iron supplements
3. Recognition of anemia symptoms and when to seek medical attention
4. Understanding the potential risks of untreated anemia to mother and baby
5. Strategies for improving iron absorption and minimizing side effects of supplements

What are effective ways to improve patient compliance with iron supplementation during pregnancy? Strategies may include educating patients about the importance of iron, addressing concerns about side effects, recommending slower-release formulations or alternative dosing schedules, and providing tips for enhancing absorption, such as taking iron with vitamin C-rich foods.

Multidisciplinary Approach to Anemia Management in Pregnancy

Effective management of anemia in pregnancy often requires a collaborative effort from various healthcare professionals:

• Obstetricians for overall pregnancy care and anemia management
• Hematologists for complex cases or rare forms of anemia
• Nutritionists for dietary counseling and supplementation strategies
• Midwives for ongoing monitoring and patient education
• Pediatricians for assessing potential impacts on the newborn

How can healthcare systems improve coordination of care for pregnant women with anemia? Implementing shared electronic health records, establishing clear referral pathways, and organizing regular case conferences can enhance communication and coordination among different specialists involved in anemia management during pregnancy.

In conclusion, understanding and managing low hematocrit values and anemia in pregnancy is crucial for ensuring the health and well-being of both mother and child. By addressing the various aspects of diagnosis, treatment, and prevention, healthcare providers can significantly reduce the risks associated with anemia during this critical period. Ongoing research and global initiatives continue to improve our approaches to this common but important pregnancy-related condition.

Anemia in Pregnancy – Gynecology and Obstetrics

By

Lara A. Friel

, MD, PhD, University of Texas Health Medical School at Houston, McGovern Medical School

Reviewed/Revised Oct 2021 | Modified Sep 2022

View Patient Education

Normally during pregnancy, erythroid hyperplasia of the marrow occurs, and red blood cell (RBC) mass increases. However, a disproportionate increase in plasma volume results in hemodilution (hydremia of pregnancy): hematocrit (Hct) decreases from between 38% and 45% in healthy women who are not pregnant to about 34% during late single pregnancy and to 30% during late multifetal pregnancy. The following hemoglobin (Hb) and Hct levels are classified as anemic:

• 1st trimester: Hb

• 2nd trimester: Hb

• 3rd trimester: Hb

If Hb is

Anemia Red Blood Cell Production Red blood cell (RBC) production (erythropoiesis) takes place in the bone marrow under the control of the hormone erythropoietin (EPO). Juxtaglomerular cells in the kidney produce erythropoietin… read more occurs in up to one third of women during the 3rd trimester. The most common causes are

• Iron deficiency Iron Deficiency Iron (Fe) is a component of hemoglobin, myoglobin, and many enzymes in the body. Heme iron is contained mainly in animal products. It is absorbed much better than nonheme iron (eg, in plants… read more

• Folate deficiency Folate Deficiency Folate deficiency is common. It may result from inadequate intake, malabsorption, or use of various drugs. Deficiency causes megaloblastic anemia (indistinguishable from that due to vitamin… read more

Obstetricians, in consultation with a perinatologist, should evaluate anemia in pregnant Jehovah’s Witness patients (who are likely to refuse blood transfusions) as soon as possible.

Early symptoms of anemia are usually nonexistent or nonspecific (eg, fatigue, weakness, light-headedness, mild dyspnea during exertion). Other symptoms and signs may include pallor and, if anemia is severe, tachycardia or hypotension.

Anemia increases risk of

• Preterm delivery Preterm Labor Labor (contractions resulting in cervical change) that begins before 37 weeks gestation is considered preterm. Risk factors include prelabor rupture of membranes, uterine abnormalities, infection… read more

• Low birth weight

• Postpartum maternal infections

Diagnosis of anemia begins with CBC; usually, if women have anemia, subsequent testing is based on whether the MCV is low ( 100 fL):

• For microcytic anemias: Evaluation includes testing for iron deficiency (measuring serum ferritin) and hemoglobinopathies Overview of Hemolytic Anemia At the end of their normal life span (about 120 days), red blood cells (RBCs) are removed from the circulation. Hemolysis is defined as premature destruction and hence a shortened RBC life span. .. read more (using hemoglobin electrophoresis). If these tests are nondiagnostic and there is no response to empiric treatment, consultation with a hematologist is usually warranted.

• For macrocytic anemias: Evaluation includes serum folate and vitamin B12 levels.

• For anemia with mixed causes: Evaluation for both types is required.

Treatment of anemia during pregnancy is directed at reversing the anemia (see below).

Transfusion is usually indicated for any anemia if severe constitutional symptoms (eg, light-headedness, weakness, fatigue) or cardiopulmonary symptoms or signs (eg, dyspnea, tachycardia, tachypnea) are present; the decision is not based on the Hct.

Pearls & Pitfalls

• Hemodilution occurs during pregnancy, but oxygen-carrying capacity remains normal throughout pregnancy.

• The most common causes of anemia during pregnancy are iron deficiency and folate acid deficiency.

• Anemia increases risk of preterm delivery and postpartum maternal infections.

• If Hb is

• Treat the cause of the anemia if possible, but if patients have severe symptoms, transfusion is usually indicated.

About 95% of anemia cases during pregnancy are iron deficiency anemia Iron Deficiency Anemia Iron deficiency is the most common cause of anemia and usually results from blood loss; malabsorption, such as occurs in celiac disease, is a much less common cause. Symptoms are usually nonspecific… read more . The cause is usually

• Inadequate dietary intake (especially in adolescent girls)

• A previous pregnancy

• The normal recurrent loss of iron in menstrual blood (which approximates the amount normally ingested each month and thus prevents iron stores from building up) before the woman became pregnant

Typically, Hct is ≤ 30%, and MCV is

One 325-mg ferrous sulfate tablet taken midmorning is usually effective. Higher or more frequent doses increase GI adverse effects, especially constipation, and one dose blocks absorption of the next dose, thereby reducing percentage intake.

About 20% of pregnant women do not absorb enough supplemental oral iron; a few of them require parenteral therapy. The iron deficit may be calculated, and the iron can often be replaced over one or two infusions. Hct or Hb is measured weekly to determine response. If iron supplements are ineffective, concomitant folate deficiency should be suspected.

Neonates of mothers with iron deficiency anemia usually have a normal Hct but decreased total iron stores and a need for early dietary iron supplements.

Although the practice is controversial, iron supplements (usually ferrous sulfate 325 mg orally once a day) are usually given routinely to pregnant women to prevent depletion of body iron stores and prevent the anemia that may result from abnormal bleeding or a subsequent pregnancy.

Folate deficiency Folate Deficiency Folate deficiency is common. It may result from inadequate intake, malabsorption, or use of various drugs. Deficiency causes megaloblastic anemia (indistinguishable from that due to vitamin… read more increases risk of neural tube defects Overview of Congenital Neurologic Anomalies Congenital brain anomalies usually cause severe neurologic deficits; some may be fatal. Some of the most serious neurologic anomalies (eg, anencephaly, encephalocele, spina bifida) develop in… read more and possibly fetal alcohol syndrome Fetal Alcohol Syndrome Alcohol exposure in utero increases the risk of spontaneous abortion, decreases birth weight, and can cause fetal alcohol syndrome, a constellation of variable physical and cognitive abnormalities… read more . Deficiency occurs in 0.5 to 1.5% of pregnant women; megaloblastic macrocytic anemia Megaloblastic Macrocytic Anemias Megaloblastic anemias result most often from deficiencies of vitamin B12 and folate. Ineffective hematopoiesis affects all cell lines but particularly red blood cells. Diagnosis is usually based… read more is present if deficiency is moderate or severe.

Rarely, severe anemia and glossitis occur.

Folate deficiency is suspected if CBC shows anemia with macrocytic indices or high RBC distribution width (RDW). Low serum folate levels confirm the diagnosis.

Treatment is folic acid 1 mg orally twice a day.

Severe megaloblastic anemia may warrant bone marrow examination and further treatment in a hospital.

For prevention, all pregnant women and women who are trying to conceive are given folic acid 0.4 to 0.8 mg orally once a day. Women who have had a fetus with spina bifida should take 4 mg once a day, starting before conception.

During pregnancy, hemoglobinopathies, particularly sickle cell disease Sickle Cell Disease Sickle cell disease (a hemoglobinopathy) causes a chronic hemolytic anemia occurring almost exclusively in people with African ancestry. It is caused by homozygous inheritance of genes for hemoglobin. .. read more , Hb S-C disease Hemoglobin S-C Disease Hemoglobin S-C disease is a hemoglobinopathy that causes symptoms similar to those of sickle cell disease, but usually less severe. (See also Overview of Hemolytic Anemia.) The heterozygous… read more , and beta- and alpha- thalassemia Thalassemias Thalassemias are a group of inherited microcytic, hemolytic anemias characterized by defective hemoglobin synthesis. Alpha-thalassemia is particularly common among people with African, Mediterranean… read more , can worsen maternal and perinatal outcomes. Genetic screening genetic screening Genetic Screening for Some Ethnic Groups for some of these disorders is available.

Preexisting sickle cell disease, particularly if severe, increases risk of the following:

• Maternal infection (most often, pneumonia Overview of Pneumonia Pneumonia is acute inflammation of the lungs caused by infection. Initial diagnosis is usually based on chest x-ray and clinical findings. Causes, symptoms, treatment, preventive measures, and… read more , urinary tract infections [UTIs] Postpartum Pyelonephritis Pyelonephritis is bacterial infection of the renal parenchyma. Pyelonephritis may occur postpartum if bacteria ascend from the bladder. The infection may begin as asymptomatic bacteriuria during… read more , and endometritis Postpartum Endometritis Postpartum endometritis is uterine infection, typically caused by bacteria ascending from the lower genital or gastrointestinal tract. Symptoms are uterine tenderness, abdominal or pelvic pain… read more )

• Pregnancy-induced hypertension Hypertension in Pregnancy Recommendations regarding classification, diagnosis, and management of hypertensive disorders (including preeclampsia) are available from the American College of Obstetricians and Gynecologists… read more

• Heart failure Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal… read more

• Pulmonary infarction Pathophysiology

• Fetal growth restriction Small-for-Gestational-Age (SGA) Infant Infants whose weight is < the 10th percentile for gestational age are classified as small for gestational age. Complications include perinatal asphyxia, meconium aspiration, polycythemia… read more

• Preterm delivery Preterm Labor Labor (contractions resulting in cervical change) that begins before 37 weeks gestation is considered preterm. Risk factors include prelabor rupture of membranes, uterine abnormalities, infection… read more

• Low birth weight Small-for-Gestational-Age (SGA) Infant Infants whose weight is < the 10th percentile for gestational age are classified as small for gestational age. Complications include perinatal asphyxia, meconium aspiration, polycythemia. .. read more

Anemia almost always becomes more severe as pregnancy progresses. Sickle cell trait increases the risk of UTIs but is not associated with severe pregnancy-related complications.

Treatment of sickle cell disease during pregnancy is complex. Painful crises should be treated aggressively. Prophylactic exchange transfusions to keep Hb A at ≥ 60% reduce risk of hemolytic crises and pulmonary complications, but they are not routinely recommended because they increase risk of transfusion reactions, hepatitis, HIV transmission, and blood group isoimmunization. Prophylactic transfusion does not appear to decrease perinatal risk. Therapeutic transfusion is indicated for the following:

• Symptomatic anemia

• Heart failure

• Severe bacterial infection

• Severe complications of labor and delivery (eg, bleeding, sepsis)

Hb S-C disease may first cause symptoms during pregnancy. The disease increases risk of pulmonary infarction by occasionally causing bony spicule embolization. Effects on the fetus are uncommon but, if they occur, often include fetal growth restriction.

Sickle cell–beta-thalassemia is similar to Hb S-C disease but is less common and more benign.

Alpha-thalassemia does not cause maternal morbidity, but if the fetus is homozygous, hydrops and fetal death occur during the 2nd or early 3rd trimester.

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Hematocrit Values in White, Black, and American Indian Children With Comparable Iron Status: Evidence to Support Uniform Diagnostic Criteria for Anemia Among All Races | JAMA Pediatrics

Hematocrit Values in White, Black, and American Indian Children With Comparable Iron Status: Evidence to Support Uniform Diagnostic Criteria for Anemia Among All Races | JAMA Pediatrics | JAMA Network










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Article

September 1984

Ray Yip, MD, MPH^{; Samuel Schwartz, MD; Amos S. Deinard, MD}

Author Affiliations

From the Department of Pediatrics, University of California, San Francisco (Dr Yip), and the Departments of Internal Medicine (Dr Schwartz) and Pediatrics (Dr Deinard), University of Minnesota, and the Bureau of Maternal and Child Health (Dr Deinard), Minneapolis.

Am J Dis Child. 1984;138(9):824-827. doi:10.1001/archpedi.1984.02140470024008

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Abstract

• We compared the hematocrit values of 425 black and 164 American Indian children with an equal number of white children who were matched for sex, age, and iron nutrition status based on serum ferritin level. Black children were found to have a mean hematocrit value 0.7% lower than that of white, matched controls. No hematocrit difference was found between American Indian children and their white controls. This finding in blacks is consistent with those of previous series, except the magnitude of the hematocrit difference is smaller. The lower value in blacks may be accounted for by mild thalassemias, which are associated with lower hematocrit values. The use of the same diagnostic criteria for anemia among all races will permit uniform detection of nutritional anemia as well as a greater rate of diagnosis of certain hereditary hemoglobinopathies.

(AJDC 1984;138:824-827)

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British scientists studied the effect of testosterone therapy on hematocrit and blood rheology

Brunel University of London conducted a meta-analysis of studies on the effect of testosterone therapy on blood parameters and concluded that an increase in hematocrit is the most common side effect of therapy. The greatest increase in the indicator is observed in patients with its initially low value. At the same time, according to the authors, there is still no convincing evidence that with an increase in hematocrit above 0.54, the dose of testosterone should be adjusted. In some groups of patients, it would be more correct to use other reference hematocrit values. The work was published in Sexual Medicine Reviews.

In recent years, the number of patients receiving testosterone replacement therapy (TRT) has been steadily increasing worldwide. However, despite the fact that most studies support the benefit of therapy, data on its safety remain controversial. In particular, there is no consensus on how the use of testosterone affects the state of the cardiovascular system. Some studies reported a reduction in the risk of cardiovascular events and mortality in patients, others proved the opposite.

British experts conducted a review of studies in which they studied how TRT affects hematocrit, blood rheology and the associated risks of cardiovascular morbidity and mortality. They also assessed the validity of current recommendations to reduce the dose of testosterone when hematocrit increases above 0.54.

More than 70 scientific publications were selected from the PubMed database, which described the benefits and possible pitfalls of TRT. To assess changes in blood parameters after 30 weeks of therapy, the authors used data from the BLAST study, conducted from Sept. 2008 to June 2012

The results of the analysis showed that TRT leads to an increase in hematocrit in patients by an average of 0.01. Initially, lower hematocrit values ​​are associated with its greatest increase during therapy.

In the BLAST study, none of the men on TRT had a hematocrit greater than 0.54. However, a clinical case reported by the University Hospitals Birmingham NHS in 2007, in which the patient’s hematocrit increased to 0.648, demonstrates the need to monitor blood parameters during therapy. The review found no scientific evidence that a hematocrit value of 0. 54 should be considered critical.

The association of hematocrit with cardiovascular morbidity and mortality, according to the authors, remains unproven, but seems likely, and, apparently, exists only in certain groups of patients. To finally clarify this issue, it is necessary to conduct new studies.

Retrieved : Sex Med Rev. 2019 Mar 26. pii: S2050-0521(19)30009-5. doi:10.1016/j.sxmr.2019.01.003

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