Fever during Pregnancy

Is a fever dangerous during a pregnancy?  Will a fever harm the baby?


A high fever (over 101 F) for a long period of time during an early pregnancy can be harmful to the fetus.  The exposure to high temperatures is most damaging between the fourth week after the last menstrual period and the fourteenth week.   In the second 3 months and the last 3 months of pregnancy, high temperatures are much less likely to cause any problems for the baby.

A brief episode of high temperature is unlikely to cause any problem and is usually treated with an over the counter medication like acetaminophen (Tylenol.)

Fever may indicate an infection in the womb which could also be harmful to the fetus. Such infections could be from the cytomegalovirus (CMV,) parvovirus, or toxoplasmosis.

Some researchers think that when the mother has a high internal temperature from fever or even soaking in the hot tub early in pregnancy there may be a greater chance of development of neural tube defects such as spina bifida-an opening in the spine.

There have been reports that there could be up to 3 times the chance of a child being diagnosed with autism by 3 years old if the mother had fever for a week or the flu during pregnancy.  The Center for Disease control says that there needs to be more research in this area to be certain.

There have been questions about other birth defects resulting from fever and infection but again more research is needed.

An ultrasound after 20 weeks may be used to look for any obvious birth defects.

Of course if the increased temperature is controlled, there would be little risk to the fetus.  If a woman develops a fever during pregnancy she should follow the instructions given to her by her health care provider.  If she is unsure, it is best to call her doctor or her nurse practitioner for further information and instructions.