Maternal high fever and newborn brain development
Fever in pregnancy is common, especially during cold and flu seasons, and in many cases it is mild and short lived. However, a **high fever in the mother, especially early in pregnancy, can affect the developing brain of the baby** and may increase the risk of certain problems. Understanding when fever matters, why it can be risky, and how to reduce those risks can help parents and caregivers make safer choices.
What counts as a high fever in pregnancy
Doctors usually consider a temperature above about 100.4°F (38°C) a fever. A mild, short lasting fever from a simple viral illness often does not cause serious harm. In contrast, a **high grade fever**, especially above about 102°F (38.9°C), and one that lasts for a long time or is caused by a severe infection, can be more worrisome during pregnancy, particularly in the first trimester when the baby’s organs and nervous system are forming.[1]
Some serious infections during pregnancy, such as meningitis or encephalitis sometimes called “brain fever,” are linked to very high temperatures and other severe symptoms like headache, stiff neck, confusion, or seizures.[1] These illnesses can be dangerous for both mother and baby and always need urgent medical care.
How fever in early pregnancy may affect the baby’s brain
During the first trimester, the baby’s brain and spinal cord start as a simple structure called the neural tube. If anything interferes with this early development, it can lead to **neural tube defects**, such as spina bifida or anencephaly. Research has found that maternal fever, particularly in early pregnancy, may increase the risk of such neural tube defects and other developmental problems.[1]
According to doctors writing about high fever in pregnancy, a strong, untreated fever in the first trimester can:
• Disturb normal formation of the neural tube
• Interfere with growth of brain and spinal cord structures
• Increase the risk of miscarriage, stillbirth, or serious birth defects when caused by severe infections[1]
Very high temperatures may affect fetal brain cells directly, since the baby cannot regulate body temperature as well as an adult and relies completely on the mother’s body for a stable environment. When the mother’s temperature rises too much, the baby’s tissues can also be stressed.
Infections behind the fever and their role in brain injury
It is important to understand that it is often **not just the fever, but the infection causing it**, that poses a risk. Some infections that give a pregnant woman a high temperature can cross the placenta or affect blood flow and oxygen delivery to the baby. These effects can disturb brain development.
For example:
• Severe infections that involve the brain or spinal cord in the mother, such as meningitis or encephalitis, are associated with a higher risk of pregnancy loss, premature birth, and developmental problems in the baby if not treated promptly.[1]
• Infections that lead to high fevers and systemic illness can also cause dehydration and low blood pressure in the mother, which may reduce oxygen and nutrient supply to the fetus and harm developing brain tissue.[1]
Even after birth, serious infections in a newborn can damage the brain. While this is slightly different from fever during pregnancy, it shows how strongly infection, fever, and inflammation are linked with brain injury.
Newborn infections, high fever, and later brain problems
Newborn babies have immature immune systems and are more vulnerable to severe infections. Doctors explain that **postnatal infections such as meningitis, encephalitis, sepsis, and severe jaundice can disturb normal brain development** and are among the strongest contributors to cerebral palsy.[2][3]
Severe infections in infants can cause:
• Inflammation and swelling of the brain
• Reduced oxygen flow to brain tissue
• Toxins or inflammatory chemicals that injure brain cells
• High fever that affects brain function
• Increased pressure inside the skull[2]
When these problems affect the parts of the brain that control movement and coordination, they can lead to **cerebral palsy**, a lifelong condition that affects muscle tone, balance, and motor skills.[2][3]
You can read more about how neonatal infections can injure the brain and cause cerebral palsy at resources such as Orange Healthcare and ChildbirthInjuries.com:
https://www.orangehealthcare.in/uncategorized/severe-infections-in-infants-leading-to-cerebral-palsy-causes-early-signs-and-prevention/
https://www.childbirthinjuries.com/cerebral-palsy/causes/neonatal-infection/
These examples in newborns highlight why preventing and promptly treating serious infections and high fever around the time of birth is so important for brain health.
Direct and indirect effects on brain development
Maternal high fever can affect the baby’s brain in more than one way.
Direct heat stress
Sustained high temperature may:
• Damage sensitive developing brain cells
• Disrupt the timing of cell growth, migration, and connections between neurons
• Interfere with how protective coverings around nerves form
These changes can potentially contribute to learning difficulties, movement problems, or other neurodevelopmental disorders later in life, especially if combined with other risk factors.
Indirect effects from infection and inflammation
The immune response to infection releases many inflammatory chemicals. Some can cross the placenta or affect placental blood flow. This may:
• Reduce oxygen and nutrients to the developing brain
• Trigger inflammation in fetal tissues
• Alter the signals that guide brain development
Severe maternal infections with high fever early in pregnancy have been linked in some studies to a higher risk of conditions like neural tube defects and possibly later neurodevelopmental issues. A discussion of these risks in relation to “brain fever” and high temperature in pregnancy is available, for example, here:
https://www.cloudninecare.com/blog/brain-fever-vs-normal-fever-in-pregnancy-key-differences
Timing matters
The stage of pregnancy when fever occurs is important.
First trimester
This is the most sensitive period for structural development of the brain and spinal cord. High grade fever and serious infections at this time are more strongly associated with:
• Neural tube defects
• Miscarriage and stillbirth
• Major organ malformations[1]
Second and third trimester
Later in pregnancy, the basic structure of the brain is already formed, but connections, growth, and maturation are still ongoing. High fever and infection at this stage can:
• Increase the risk of preterm birth
• Contribute to problems like low oxygen supply, which can injur
