Mean corpuscular hemoglobin (MCH)
MCH reflects the average amount of hemoglobin per red blood cell. Values change minimally during pregnancy and generally parallel the MCV.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| pg/cell | 27–32 | 30–32 | 30–33 | 29–32 |
Pregnancy physiology
- MCH changes minimally across gestation.
- Small increases reflect physiologic macrocytosis in some pregnancies.
- Values parallel MCV and help classify anemia as microcytic, normocytic, or macrocytic.
Causes of decreased MCH (hypochromia)
- Iron deficiency anemia — most common in pregnancy
- Thalassemia trait (α or β)
- Anemia of chronic inflammation
- Sideroblastic anemia
- Chronic bleeding / nutritional deficiency
Cited references:
• Abbassi-Ghanavati M et al., Obstet Gynecol 2009.
• Fischbach & Dunning — Manual of Laboratory and Diagnostic Tests.
• Gronowski AM — Laboratory Testing in Pregnancy.
Causes of increased MCH (macrocytosis)
- Normal pregnancy (mild physiologic macrocytosis)
- Vitamin B12 deficiency (pernicious anemia, malabsorption)
- Folate deficiency (nutritional, malabsorption, alcoholism)
- Hypothyroidism
- Liver disease
- Myelodysplastic syndromes
- Medications (methotrexate, zidovudine, hydroxyurea, anticonvulsants)
Cited references:
• Chanarin I et al., BJOG 1977 — Physiologic macrocytosis of pregnancy.
• Wallach J — Interpretation of Diagnostic Tests.
• Dunning & Fischbach — Laboratory and Diagnostic Tests.
References
- Lockitch G. Handbook of Diagnostic Biochemistry and Hematology in Normal Pregnancy. CRC Press; 1993.
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.
- Fischbach FT, Dunning MB. A Manual of Laboratory and Diagnostic Tests, 7th ed. LWW, 2004.
- Chanarin I, et al. Physiologic macrocytosis in pregnancy. Br J Obstet Gynaecol. 1977;84:504–8.