Having a fever during pregnancy, particularly in the first trimester, can cause problems for a developing baby – but researchers do not yet know whether having a fever during early pregnancy may actually cause a miscarriage. It is usually prolonged, high fevers that are thought to cause problems.
Some research does link hyperthermia, or abnormally high body temperature, to risk of neural tube defects and possibly miscarriage. One 2003 study looked at hot tub use and found weak evidence of an association between hot tubs and miscarriages -– and doctors routinely advise pregnant women to avoid soaking in hot baths for extended periods of time to be on the safe side.
Research looking specifically at maternal fevers has found that fevers seem to increase the risk of neural tube defects. (The most severe neural tube defects, such as anencephaly, can be fatal for the baby and thus cause pregnancy loss). Fevers may also increase the risk of other developmental problems, such as heart defects.
The verdicts have been less conclusive as to whether fever causes first-trimester miscarriage; a large 2002 study in "The Lancet" found no evidence of an association, although a 1985 case control study by Johns Hopkins University researchers had hinted at a link between fever and miscarriage.
Because of the possible risk of developmental problems, doctors often advise pregnant women to call when experiencing a fever over 101 degrees Fahrenheit. Remember to call your doctor if you are ever concerned about illness or other symptoms during pregnancy.
Sources:
Anderson, Anne-Marie Nybo, Pernille Vastrup, Jan Wohlfahrt, Per Kragh Anderson, Jorn Olsen, and Mads Melbye. "Fever in pregnancy and risk of fetal death: a cohort study. The Lancet 2002. Accessed 6 Jan 2008.
Botto, L.D., M.C. Lynberg, and J.D. Erickson. "Congenital heart defects, maternal febrile illness, and multivitamin use: A population-based study." Epidemiology Sept 2001. Accessed 6 Jan 2008.
Chambers, Christina, Kathleen A. Johnson, Lyn M. Dick, Robert J. Felix, and Kenneth Lyons Jones. "Maternal fever and birth outcome: A prospective study." Teratology 1999. Accessed 6 Jan 2008.
Kline, Jennie, Zena Stein, Mervyn Susser, and Dorothy Warburton. "Fever During Pregnancy and Spontaneous Abortion." American Journal of Epidemiology 1985. Accessed 6 Jan 2008.
Li, De-Kun, Teresa Janevic, Roxana Odouli, and Liyan Liu. "Hot Tub Use during Pregnancy and the Risk of Miscarriage." American Journal of Epidemiology 2003. Accessed 6 Jan 2008.
