Most parents expect labor to be physically demanding, but few realize that maternal fever during labor is relatively common, affecting approximately 1 in 10 laboring patients. While many fevers resolve without causing serious problems, growing research suggests that maternal fever may be associated with an increased risk of Hypoxic-Ischemic Encephalopathy (HIE), a type of newborn brain injury caused by insufficient oxygen and blood flow around the time of birth.
A major population-based study published in the American Journal of Obstetrics and Gynecology (AJOG) in 2025 suggests that maternal fever is more than just a symptom of labor, it may be an important warning sign that requires careful monitoring of both mother and baby. The research revealed a clear pattern: the higher a mother’s temperature rises and the longer her fever persists before delivery, the greater the baby’s risk of developing HIE and other severe neonatal complications.
It is important to understand that this study found an association, not proof that maternal fever directly causes HIE. Many factors can contribute to neonatal brain injury, and maternal fever represents one important piece of the overall clinical picture.
Here’s what parents should know.
What Is Maternal Fever?
Maternal fever, also called intrapartum fever, is generally defined as a body temperature of 100.4°F (38°C) or higher during labor.
It affects approximately 1 in 10 women during labor and can develop for several reasons. The two most common causes are:
- Infection inside the uterus, such as chorioamnionitis (also called an intra-amniotic infection)
- Fever associated with epidural anesthesia, which may occur even when no infection is present
Epidural anesthesia remains a safe and effective form of pain relief during labor. Although epidurals are commonly associated with maternal fever, this study found that fevers beginning before epidural placement were associated with a higher risk of HIE than fevers developing afterward, suggesting that underlying infection may play an important role in some cases.
What Is HIE?
Hypoxic-ischemic encephalopathy (HIE) is a type of brain injury caused when a baby’s brain does not receive enough oxygen and blood flow around the time of birth.
HIE can lead to lifelong disabilities, including:
- Cerebral palsy
- Developmental delays
- Learning disabilities
- Epilepsy
- Vision or hearing impairments
HIE can range from mild to severe. Some babies recover with few long-term effects, while others may develop conditions such as cerebral palsy, epilepsy, developmental delays, or learning disabilities.
Not every baby exposed to maternal fever develops HIE. However, research suggests maternal fever is one of several important risk factors that healthcare providers should take seriously during labor.
What the Research Reveals: Temperature, Duration, and Risk
The AJOG study evaluated outcomes across nearly 250,000 laboring mothers (excluding elective C-sections) across 15 hospitals over a seven-year period. The findings demonstrated a direct relationship between maternal hyperthermia and neonatal brain injury.
1. Overall Risk and Temperature Severity
Overall, babies born to mothers who developed a fever during labor were nearly 4 times more likely to develop HIE compared to those whose mothers did not develop a fever.
2. Duration of Fever Exposure
The amount of time a baby spends exposed to elevated maternal temperatures is just as critical as the height of the fever itself:
- Babies exposed to maternal fever for less than 1 hour before delivery had the lowest incidence of HIE (0.23%).
- Babies whose mothers had a fever for 6 hours or longer prior to delivery faced 2.4times the risk of HIE compared to those exposed for only 1 to 3 hours.
3. Even Mild Temperature Increases May Matter
One of the study’s most interesting findings was that increased risk was observed even among mothers whose highest recorded temperature remained below the traditional definition of fever (38°C).
Women whose highest temperature was between 37.5°C and 37.9°C also had a higher risk of delivering a baby with HIE compared with mothers whose temperatures remained below 37.5°C.
Researchers believe this may occur because a baby’s core body temperature is naturally higher than the mother’s. Even a small increase in maternal temperature may translate into a significantly higher fetal brain temperature, potentially making the brain more vulnerable if oxygen delivery becomes compromised during labor.
4. Why Might Maternal Fever Increase the Risk of HIE?
Researchers are still working to understand exactly why maternal fever is associated with HIE, but several biologic mechanisms have been proposed.
A mother’s temperature is naturally lower than her baby’s core temperature during labor. Even relatively small increases in maternal temperature may result in a greater increase in fetal brain temperature, potentially making the brain more vulnerable if oxygen delivery becomes compromised.
Maternal infection and inflammation may also increase the baby’s metabolic demands during labor. Rather than proving that fever directly causes brain injury, current evidence suggests that maternal fever may reduce the fetus’s ability to tolerate other stresses occurring during labor.
More research is needed to determine whether interventions that reduce maternal fever can improve neonatal outcomes.
5. Infectious Fevers vs. Epidural Fevers
The research noted a distinct difference depending on when the fever initiated:
- Fevers that began before an epidural was placed carried nearly double the risk of HIE compared to fevers that developed after epidural placement.
- This suggests that underlying uterine infections (such as chorioamnionitis) may impose greater metabolic strain on the baby than epidural-induced temperature rises alone.
6. Maternal Fever Was Associated With Other Serious Newborn Complications
The study found that increasing maternal temperature was also associated with a greater risk of:
- Low Apgar scores
- Metabolic acidosis
- Neonatal seizures
- Therapeutic hypothermia (cooling treatment)
- NICU admission
- Early-onset neonatal sepsis
In general, both higher temperatures and longer fever duration were associated with worse neonatal outcomes.
Does Maternal Fever Directly Cause HIE?
Not necessarily. This study found a strong association, but it did not prove that maternal fever directly causes HIE.
Many other factors including infection, placental problems, prolonged labor, umbilical cord complications, and fetal distress can contribute to HIE.
However, even after adjusting for labor duration, researchers found that both the severity of maternal fever and how long it lasted remained independently associated with an increased risk of HIE.
What Should Healthcare Providers Do?
Maternal fever should never be ignored during labor.
When a fever develops, healthcare providers should carefully evaluate both the mother and baby. Depending on the clinical situation, this may include:
- Identifying the cause of the fever
- Evaluating for intra-amniotic infection
- Administering antibiotics when infection is suspected
- Giving medications to reduce fever when appropriate
- Closely monitoring the baby’s heart rate for signs of distress
- Reassessing whether delivery should be expedited if the baby shows evidence of oxygen deprivation
The AJOG study does not conclude that every mother with a fever should undergo an emergency cesarean section. In fact, the authors caution that the study does not prove that earlier cesarean delivery would prevent HIE. Instead, they emphasize the importance of recognizing maternal fever as an important clinical risk factor that should prompt careful monitoring and timely medical decision-making.
When Can Maternal Fever Become a Birth Injury Case?
Maternal fever itself is not medical negligence. When evaluating a birth injury case, experts do not look at maternal fever in isolation. They evaluate the entire clinical picture, including maternal temperature, fetal heart rate patterns, labor progression, suspected infection, cord blood gases (when available), and the healthcare team’s response to determine whether the standard of care was met.
However, healthcare providers may fail to meet the standard of care if they do not appropriately respond to signs that a baby may be in distress.
Depending on the circumstances, concerns may arise if providers fail to:
- Recognize or document maternal fever
- Investigate a possible intra-amniotic infection
- Monitor fetal heart rate appropriately
- Respond to signs of fetal distress
- Provide timely treatment or delivery when clinically indicated
Every labor is unique, and the presence of maternal fever alone does not mean malpractice occurred. A thorough review of the medical records is necessary to determine whether healthcare providers acted appropriately under the circumstances.
Frequently Asked Questions
Does maternal fever always cause HIE?
No. Most babies born to mothers with a fever do not develop HIE. Maternal fever is one of many factors that may increase risk but does not, by itself, cause brain injury.
Can an epidural cause maternal fever?
Yes. Epidural-related fever is a recognized phenomenon and often occurs without infection. This study suggests that fevers beginning before epidural placement may carry a higher risk than fevers developing afterward.
What temperature is considered a fever during labor?
Maternal fever during labor is generally defined as a temperature of 100.4°F (38°C) or higher. However, this study found increased risk beginning with temperatures between 37.5°C and 37.9°C, even before the traditional fever threshold.
Does every mother with a fever need a Cesarean section?
No. The study does not conclude that maternal fever alone should lead to an emergency Cesarean delivery. Instead, it highlights maternal fever as an important clinical finding that should prompt careful monitoring of both mother and baby.
The Bottomline
Research increasingly shows that both the severity of maternal fever and the length of time it persists before delivery are associated with an increased risk of HIE and other serious newborn complications.
While maternal fever does not automatically cause HIE, it is an important warning sign that requires careful assessment and ongoing monitoring throughout labor. Early recognition and appropriate medical management may help identify babies at increased risk and improve neonatal outcomes.
References
- Cornet MC, Kuzniewicz MW, Scheffler AW, Garabedian C, Gaw SL, Wu YW. Maternal Fever During Labor and the Risk of Neonatal Encephalopathy: Duration and Magnitude of Hyperthermia. American Journal of Obstetrics & Gynecology. 2025;233(6):651.e1-651.e12. https://doi.org/10.1016/j.ajog.2025.07.046.
Disclaimer
The information provided on Lirowiller Law is for general informational and educational purposes only and does not constitute legal or medical advice. The content of this article is not intended to be a substitute for professional medical diagnosis or treatment, nor should it be relied upon as legal counsel for any specific case. Reading or interacting with this content does not establish an attorney-client relationship. If you have concerns about your child’s health, please consult a qualified healthcare provider. If you suspect your child has suffered a preventable birth injury, contact an experienced medical malpractice attorney for a personalized case evaluation.