A high white blood cell count is known as leukocytosis, and it is common in pregnancy, especially in the third trimester.
But high WBC in pregnancy can also be a symptom of infection, inflammation, an autoimmune disorder, or a malignancy such as leukemia.
Here’s what to know about a high white blood cell count in pregnancy.
What Are White Blood Cells?
White blood cells, called leukocytes, help your body fight infection. There are five different types of leukocytes in human blood, each with a specific job to do [*]:
- Neutrophils and monocytes fight bacterial infection and repair damaged tissue. Neutrophils are the most plentiful type of white blood cell.
- Lymphocytes are white blood cells that protect your lymphatic system. They can be T-cells or B-cells which fight off viruses and foreign organisms by producing antibodies.
- Eosinophils and basophils are white blood cells that fight infections and inflammation arising from things like allergic reactions, parasitic infections, and autoimmune disorders.
Blood is composed of these white blood cells as well as oxygen-carrying red blood cells, platelets that help blood clot, and plasma, the liquid portion of blood [*].
What Is a High White Blood Cell Count During Pregnancy?
The normal range for WBC count in a woman is between 4,500 - 11,000 WBCs per microliter (µL). In pregnant women, some sources cite the acceptable range in the third trimester as 12,000-18,000 WBCs per µL but reference intervals vary widely between sources [*][*].
WBC counts typically rise as the pregnancy progresses, peaking just after delivery, then return to normal (non-pregnancy) levels in the weeks after childbirth.
A 2021 UK study with the largest cohort to date (more than 24,000 women) found total WBC count to be elevated by 36% in pregnancy, largely due to a 55% increase in neutrophils and 38% increase in monocytes [*].
The day after delivery, the UK study found WBC counts ranging from 8,400 - 23,300 WBCs per µL, probably in response to the trauma of childbirth [*].
Is High WBC in Pregnancy Normal?
Generally speaking, yes, high WBC in pregnancy is considered normal if no other abnormal symptoms are present, such as fever, night sweats, or pain. The acceptable range for WBC in pregnancy varies based on a number of factors, including age, weight, and how far along the pregnancy is [*].
What Causes a High White Blood Cell Count During Pregnancy?
While doctors don’t know exactly what causes high WBC in pregnancy for all women, the physiological and emotional stress of pregnancy is chief among the reasons.
Pregnancy is marked by intense physiological changes, not the least of which is a 50% increase in blood volume — about an extra 1.5 liters. This increase helps supply the placenta and fetus with needed blood and compensate for blood loss that can occur with delivery [*].
It’s not hard to imagine that keeping a developing fetus with no immune system free of infection in the womb might have something to do with increased white blood cell production, especially neutrophils. However, high WBC in pregnancy can also be increased by:
These include epinephrine, corticosteroids, heparin, aspirin, allopurinol, quinine, triamterene and chloroform.
Smoking is a cause of elevated WBC count in adults whether or not they are pregnant. Quitting smoking leads to recovery of WBC counts within a year [*].
One of the challenges of adopting a specific reference interval for WBC count arises from differences in race. For instance, one study showed that black people have a lower total WBC count, with lower neutrophils and higher lymphocytes, than their nonblack counterparts [*].
High BMI or Obesity
Obesity is characterized as a chronic inflammatory condition and is associated with a high WBC count [*].
Physical exertion, whether mild or strenuous, increases WBC is pregnant and nonpregnant women alike (as well as men) [*].
Allergic Reaction or Chronic Inflammatory Condition
An allergic reaction will cause WBC count to increase in pregnancy. An autoimmune disease like lupus or rheumatoid arthritis will also cause WBC count to rise.
Chorioamnionitis is an inflammation of the fetal membranes after 20 weeks’ gestation. Maternal WBC typically exceeds 15,000 and is accompanied by maternal and fetal tachycardia, uterine tenderness, and foul-smelling amniotic fluid. Endometritis is an infection of the uterus more commonly found after birth. It’s a little more common among women who have had a c-section [*].
While it’s rare for malignancies to arise during pregnancy, when they do, they can often go undetected, masked by the symptoms of pregnancy. Recently, researchers have found that false-positive or nonreportable non-invasive pregnancy testing (NIPT) for the fetus has the potential to reveal certain maternal cancers because it can detect DNA fragments shed by a tumor [*].
What Are the Symptoms of a High White Blood Cell Count?
Pregnant women whose high WBC owes to the stress of being pregnant will likely not experience any symptoms in tandem with a high white blood cell count. But when the high WBC is the result of something other than pregnancy, they may experience symptoms of infection such as:
- Night sweats
- Weight loss
If you have any of these symptoms, contact your care team immediately.
Does High WBC in Pregnancy Mean Preeclampsia?
A 2019 study showed that the neutrophil-to-lymphocyte (NLR) ratio and platelet-to-lymphocyte (PLR) ratio to be higher in women with preeclampsia than in those without. The researchers posit that measuring NLR and PLR in prenatal follow-up may be useful in predicting preeclampsia for women at elevated risk [*].
A 2023 study noted that a wide range of immune cells — including T-cells, B-cells, and neutrophils — have a major causative role in the pathology of preeclampsia, which many researchers now classify as a pregnancy-induced autoimmune disorder [*][*].
Does High WBC Mean Gestational Diabetes?
Not necessarily, but there is a correlation when combined with other blood factors.
In one study of East Asian women, those who had a high WBC count early in pregnancy had a significantly higher rate of gestational diabetes mellitus (GDM) than women with a normal WBC count [*].
Other studies have indicated a direct and significant correlation between platelet and inflammatory indices (including WBC count) on the CBC test in the second trimester and gestational diabetes [*].
How Is a High White Blood Cell Count Treated?
Your care team will draw blood during the course of your pregnancy to monitor your levels — both red and white blood cells.
If your doctor believes the high WBC is due to pregnancy with no other aggravating factor and it is within normal parameters for your age, race, and gestation, no treatment is needed.
If there are other factors along with high WBC in pregnancy that suggest infection or an inflammatory or autoimmune condition, your doctor will perform other tests and may prescribe an antibiotic or other medication.
You will also be monitored after childbirth to ensure your white blood cell count goes down to normal levels.
High WBC in Pregnancy Outlook
If your doctor tells you your white blood cell count is high in pregnancy, it’s usually not cause for alarm if there are no accompanying symptoms of infection or inflammation.
If you know you have a high WBC count in pregnancy and begin to experience unusual fatigue, fever, pain, or other abnormal symptoms, be on the safe side and contact your care team immediately.
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The Bottom Line
With half of all maternal deaths worldwide stemming from infection, it’s critical that clinicians recognize the signs of infection in pregnant women.
An elevated WBC count in pregnancy is considered normal but the reference interval — the range considered normal — actually varies considerably by the mother’s age, weeks of gestation, BMI, and race. Other factors such as medication and chronic inflammatory conditions can also drive WBC count higher.
The good news is that researchers are making strides in establishing more accurate WBC reference intervals as well as identifying women predisposed to conditions such as gestational diabetes and preeclampsia based on blood markers [*].
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