INTRODUCTION

The work-up of fever in pregnancy requires special consideration of the effect of fever itself on the fetus, the impact of the pregnant state on the etiologic illness, the impact of the illness on the pregnancy, and the limitations that concerns for fetal well-being may place on diagnostic and therapeutic modalities.

The definition of fever in pregnancy is 100.4°F or 38.0°C. The normal fetal heart rate is between 110 and 160 beats per minute. Maternal fever often causes a fetal tachycardia, sometimes up to 180–200 beats per minute. It is important to treat maternal fever with antipyretics, especially in the first trimester, to decrease the risk of birth defects. The consequences of an episode of hyperthermia depend on the extent of the temperature elevation, its duration, and the stage of fetal development. Mild exposures during the preimplantation period and more severe exposures during embryonic and fetal development can result in miscarriage. Hyperthermia (usually at a level of 2.0°C elevation over normal) can cause a wide range of structural and functional defects in the fetus, ranging from central nervous system defects to growth issues. Pregnant women are also advised to be cautious about hot tubs or spa use in early pregnancy, based on their possibility of raising core maternal temperature.