Can a Fever During Pregnancy Harm My Baby?

Fever Pregnancy

When you’re pregnant, almost all of your actions bring to mind one thought: is this good or bad for the baby? This is especially true when it comes to your own health and body. When pregnant women get sick, they often ask if a fever can harm the baby. Unfortunately, the short answer is yes, a fever during pregnancy may harm your baby. However, there are things you can do to help.

Good News

Approximately one in five women report having had at least one fever during pregnancy. Due to the frequent occurrence of fever in pregnant women, along with the fear of fever and its possible consequences, multiple studies have been undertaken to identify the true nature of this problem.

A recent meta-analysis reviewed 46 studies of maternal fever. Most of the studies focused on fever in the first trimester, as this is when the developing fetus is most at risk. The authors looked at studies only from 1990-2013 and focused both on short-term outcomes (such as miscarriages) and long-term outcomes (health effects later in life).

The good news is that the authors found that fever had no effect on the risk of adverse pregnancy outcomes, such as miscarriages, stillbirth, or preterm delivery. The authors were surprised by this finding, as this is commonly seen in studies in a variety of animals. Perhaps the fevers experienced by pregnant women never got high enough to cause these outcomes, but that finding was consistent across all studies.

Bad News

However, there was an increased risk of some birth defects associated with maternal fever in the first trimester. Specifically, there was strong evidence that fevers increased the risk of neural tube defects, congenital heart defects, and cleft lip and palate. Neural tube defects are congenital defects of the brain, spine, or spinal cord, such as spina bifida.

This finding was seen in multiple studies and strongest for neural tube defects. Maternal fever in the first trimester led to an almost three-fold increased risk of neural tube defects.

The evidence suggests that maternal fever, especially in the first trimester, probably does increase the risk of some birth defects.

In multiple studies, maternal fever doubled the risk of cleft lip or palate. And the risk of congenital heart defects, like Tetralogy of Fallot or ventricular septal defect, was increased about 1.5 times.

As for other birth defects, such as malformations of the anorectal area, ears, eyes, or kidneys, some studies found an association between maternal fever and these defects, but the evidence overall was too weak to draw any conclusions about this relationship.

Interestingly, the authors did not find any association with the height of the fever and the birth defects. That is, higher fevers did not cause more or worse defects than low-grade fevers.

More Good News

The authors also investigated whether the various studies found any association with long-term outcomes in the children as they aged. Various diseases such as allergic diseases, autism, cerebral palsy, attention deficit hyperactivity disorder (ADHD), seizures, and schizophrenia were studied, but no association between fever and these diseases was found.

In addition, the authors found that the use of anti-fever medicine may have a protective effect. Although two studies found an increased risk of birth defects with anti-fever medicines, 11 studies found that such medicine reduced the risk of birth defects. In three of those studies, the risk was totally eliminated with the use of anti-fever medicine.

This finding suggests that it may truly be the fever itself, rather than the disease that causes the fever, that is the true culprit in the development of the adverse outcome.

The good news is that perhaps aggressive management of fever may be able to prevent these outcomes. Multiple studies have specifically investigated whether prenatal use of acetaminophen, specifically, is associated with adverse neurobehavioral outcomes in children. In 2015, the U.S. Food and Drug Administration reviewed the studies and found evidence was inconclusive regarding a connection between acetaminophen use in pregnancy and ADHD in the children.

Furthermore, a more recent paper published in 2017 studied over 77,000 pregnancies in Denmark. The authors also found an association between maternal fever and birth defects, but the risk was much smaller than the earlier meta-analysis quoted above. This Danish study found there was a 1.3 increased risk of defects of the eye, ear, face and neck and a 1.2 increased risk of defects of the genitals. Contrary to the prior study, they found a lower risk of defects of the nervous system, respiratory system, and urinary system.

So what does this all mean for the pregnant woman? The evidence suggests that maternal fever, especially in the first trimester, probably does increase the risk of some birth defects. So do what you can to stay as healthy as possible, such as avoiding places where infections are liable to be passed on to you. Call your doctor as soon as you get a fever to find out if you should take an anti-fever medicine and, if so, which one.

Ruben Rucoba
Dr. Rucoba has over 25 years of experience as a primary care pediatrician after completing medical school at the University of California, San Francisco. His clinical areas of expertise include caring for children with special health care needs and assisting families with international adoption. He has been a freelance medical writer since 2010, writing for health websites, continuing medical education providers, and various print outlets. He currently works at Wheaton Pediatrics in the suburbs of Chicago, where he lives with his wife and four daughters, including a set of twins.

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