A pregnant person’s white blood cell count may increase throughout pregnancy and immediately after. Treatment is usually unnecessary unless there is an underlying infection.

White blood cells (WBCs), or “leukocytes,” make up 1% of a person’s blood. WBCs fight against viruses, parasites, and bacteria. The bone marrow produces more WBCs when fighting an infection.

After an infection, memory cells remember the antigens to fight in the event of a second exposure. WBCs respond immediately to produce antibodies and prevent another illness.

Pregnant people typically have an elevated WBC count. This article discusses the causes, possible symptoms, when to contact a doctor, and the outlook.

In nonpregnant adult females, doctors consider a WBC count high when it is over 11,000 per microliter (µL) of blood. This is known as “leukocytosis.” The usual range of WBCs for females is 4,500–11,000 in 1 µL of blood, which is equivalent to 17–40 million WBCs in every teaspoon of blood.

In pregnant people, the average range of WBCs is 5,700–15,000 per 1 µL of blood. The upper limit is around 13,800–19,600.

Doctors regularly monitor WBCs during pregnancy to detect infection and inflammation. An elevated WBC count in pregnant people is common due to the body changing to carry a fetus.

A 2021 study of 24,318 pregnant people showed their total WBC count increased between 8 and 40 weeks of gestation. Certain types of WBCs increased while others remained stable or decreased.

While a pregnant person may not have leukocytosis during their pregnancy, the stress the body experiences during delivery may lead to short-term leukocytosis.

A high WBC count during pregnancy is normal, and doctors do not typically recommend treatment unless blood tests suggest an infection or a person experiences symptoms such as fever and high blood pressure.

High WBC counts have an association with preeclampsia, a condition that usually develops in the third trimester of pregnancy and causes a sudden rise in blood pressure.

Preeclampsia is serious and requires immediate treatment. In preeclampsia, an elevated WBC count is due to an increased inflammatory response.

Learn more about white blood cells.

When a person has a high WBC count, their neutrophils, a type of WBC, are higher than usual, typically due to infection. The body’s inflammatory response is to increase immature cells, which leave the bone marrow too soon and enter the bloodstream.

A high WBC count can have numerous causes, including:

A high WBC count during pregnancy may not cause symptoms. Doctors may treat the underlying cause when a person has the following symptoms:

A pregnant person should have regular contact with a healthcare team during pregnancy to monitor their health, including their WBC count.

If a pregnant person develops signs of an infection or feels unwell, they should check with a doctor.

A doctor may need to order further tests to make a diagnosis and determine a treatment plan. Sometimes, doctors prescribe antibiotics or anti-inflammatory medications to treat leukocytosis.

WBC counts usually rise during pregnancy, peak after delivery, and gradually return to nonpregnancy levels.

A 2021 study reported that total WBC counts increased significantly on the first day after delivery, ranging from 8,400–23,200 WBCs per 1 µL of blood. On average, people who had a vaginal delivery had a larger increase in their WBC counts than those who had a cesarean delivery.

By the seventh day after delivery, the average WBC count returned to the average WBC count during pregnancy. After that, it continued to fall, reaching nonpregnancy levels within 21 days.

White blood cells rise during pregnancy, peak around delivery, and fall gradually to normal levels within the first few weeks after delivery.

Healthcare teams regularly monitor the WBC counts of pregnant people. If a person has significantly elevated WBCs alongside symptoms such as fever or high blood pressure, doctors may order tests to diagnose the cause. If infection is present, they may prescribe antibiotics.

A high WBC count usually resolves without treatment.