What is the significance of an elevated white blood cell (WBC) count in pregnancy?

Elevated WBC in Pregnancy: Clinical Significance and Management

An elevated WBC count in pregnancy is a normal physiological finding, with upper reference limits reaching 15.0×10⁹/L during gestation and 25.3×10⁹/L during labor, driven primarily by neutrophilia; clinical concern should focus on accompanying symptoms of infection rather than the absolute WBC value alone. 1, 2

Normal Physiological Changes

Pregnancy induces substantial leukocytosis that must be distinguished from pathological elevations:

• Upper reference limit increases by 36% during pregnancy (5.7-15.0×10⁹/L) compared to non-pregnant state, remaining stable from 8-40 weeks gestation 1
• Neutrophils drive this increase, rising by 55% (3.7-11.6×10⁹/L) while lymphocytes decrease by 36% (1.0-2.9×10⁹/L) 1
• Labor causes further elevation, with normal range extending to 5.3-25.3×10⁹/L during active labor 2
• Postpartum surge occurs immediately after delivery (regardless of delivery mode), resolving to pre-delivery levels by day 7 and pre-pregnancy levels by day 21 1

The threshold regression model supports partitioned intervals: 4.0-10.0×10⁹/L for ≤2 weeks gestation, 4.7-11.9×10⁹/L for 3-5 weeks, and 5.7-14.4×10⁹/L for ≥6 weeks 3

When to Investigate Elevated WBC

Initiate sepsis workup when fever accompanies leukocytosis (temperature >38°C or <36°C), as this combination triggers mandatory sepsis screening 4

Specific red flags requiring immediate investigation include:

• Symptomatic infection indicators: dysuria, respiratory symptoms, wound infection, or altered mental status 4
• Severe leukopenia (WBC <5,000/µL) with lymphopenia, indicating severe infection with high mortality risk 4
• Persistent asymptomatic leukocytosis >20×10⁹/L lasting multiple weeks, though rare cases of pregnancy-induced leukocytosis may resolve only with delivery 5

Diagnostic Algorithm for Suspected Infection

When clinical suspicion exists, proceed systematically:

1. Obtain blood cultures before antibiotics if sepsis is suspected 4
2. Complete blood count with differential to assess neutrophil percentage and band forms 4
3. Left shift analysis: band neutrophils ≥6% or absolute band count ≥1,500/mm³ has a likelihood ratio of 14.5 for bacterial infection 4
4. Lactate level: >2 mmol/L outside labor suggests sepsis 4

Management of Confirmed Infection

Initiate empiric antibiotics immediately after cultures are obtained when sepsis criteria are met 4:

• Recommended regimen: ampicillin 100-150 mg/kg/day IV divided every 8-12 hours, plus gentamicin or cefotaxime for gram-negative coverage 4
• Do not delay antibiotics while awaiting culture results in symptomatic patients with suspected sepsis 4

Markers of severe sepsis requiring ICU care include:

• Persistent hypotension (SBP <90 mmHg or MAP <65 mmHg) after fluid resuscitation, defining septic shock 4
• Organ dysfunction markers: platelets <100×10⁹/L, creatinine >1.2 mg/dL, bilirubin >2 mg/dL, or new respiratory failure 4

Special Clinical Scenarios

COVID-19 infection can cause leukocytosis with elevated CRP levels higher than typical pregnancy values, with asymptomatic pre-partum patients potentially becoming symptomatic postpartum 6

Pregnancy-induced leukocytosis (non-infectious WBC >20×10⁹/L persisting throughout pregnancy) is rare but documented, with pregnancy termination being the definitive treatment when malignant leukocytosis occurs 5

Elevated WBC with pregnancy complications: Women with persistently high WBC counts show increased incidence of placenta previa, oligohydramnios, secondary uterine inertia, and intrauterine growth restriction 3

Critical Pitfalls to Avoid

• Do not use non-pregnant reference ranges when interpreting WBC counts during pregnancy or the first week postpartum 1
• Do not assume infection based solely on WBC elevation without accompanying clinical symptoms or fever 4, 2
• Do not overlook leukopenia, as WBC <5,000/µL carries higher mortality risk than leukocytosis 4
• Do not interpret labor WBC values using standard pregnancy ranges, as values up to 25.3×10⁹/L are physiologically normal during active labor 2