Does pregnancy cause an increase in absolute neutrophil (white blood cell) count?

Neutrophil Changes During Pregnancy

Yes, pregnancy causes an increase in absolute neutrophil count as part of the normal physiological adaptation to pregnancy. This neutrophilia is a well-documented phenomenon that begins in early pregnancy and persists throughout gestation.

Physiological Changes in Neutrophils During Pregnancy

Normal Neutrophil Changes

• Pregnancy induces a significant neutrophilia (increased neutrophil count) as part of normal physiological adaptation 1
• Absolute neutrophil counts progressively increase during pregnancy, with studies showing approximately a 10% decrease in overall platelet count by the third trimester 2
• This neutrophilia is caused by a combination of:
  • Hemodilution
  • Increased neutrophil activation
  • Increased neutrophil clearance 2
  • Delayed neutrophil apoptosis (programmed cell death) 1

Mechanism of Neutrophil Increase

• Research demonstrates that impaired neutrophil apoptosis (delayed cell death) explains the neutrophilia associated with normal pregnancy 1
• As gestational age increases, spontaneous neutrophil apoptosis decreases, contributing to higher circulating neutrophil counts 1
• Neutrophil function is also altered during pregnancy, with studies showing attenuated respiratory burst activity in the second and third trimesters 3

Clinical Implications

Interpretation of Laboratory Values

• When interpreting complete blood counts during pregnancy, clinicians should expect higher absolute neutrophil counts compared to non-pregnant reference ranges
• The neutrophilia of pregnancy is a normal finding and should not be misinterpreted as indicating infection or inflammation
• Neutrophil counts typically return to normal within 8 weeks of delivery 3

Differential Diagnosis

• While neutrophilia is normal in pregnancy, extremely elevated neutrophil counts may still indicate underlying pathology
• In certain pregnancy complications like preeclampsia, neutrophil activation is even more pronounced than in normal pregnancy 1, 4
• Very high neutrophil-to-lymphocyte ratios (NLR >5.8) have been associated with increased risk of miscarriage 5

Special Considerations

Pregnancy Complications

• In preeclampsia, neutrophil activation is markedly increased compared to normal pregnancy 1, 4
• Placental factors can activate neutrophils by increasing superoxide generation and modulating adhesion molecule expression 4
• Neutrophils appear to play a role in modulating the maternal response in conditions like preeclampsia and intrauterine growth restriction 1

Immune Response During Pregnancy

• Pregnancy tailors the immune responses of circulating monocytes and neutrophils to endotoxin and other bacterial products 6
• Pregnant women show increased number, phagocytic activity, and reactive oxygen species production capacity in both monocytes and neutrophils compared to non-pregnant women 6

In conclusion, the increase in absolute neutrophil count during pregnancy is a normal physiological adaptation and should be considered when interpreting laboratory results in pregnant women.