A fever during pregnancy will affect the fetus to some extent, but the specific size of the impact on the fetus depends on the degree of the fever and the length of the fever, as follows: 1. Less impact: If the fever is mild, such as a temperature of 38 ℃ or less, and occurs for a relatively short period of time, it generally has less impact on the fetus, for example, it may only cause an increase in the number of fetal movements. 2. More impact: If the fever persists, especially if it is persistently high, such as a temperature of 39 ℃ or more, it may lead to a significant increase in fetal heartbeat and even cause intrauterine distress. The fetal heartbeat may increase significantly and even cause intrauterine distress if the fetus is in a constant state of high fever, such as a temperature of 39°C or more. Therefore, in case of persistent high fever during pregnancy, it is necessary to consult a doctor promptly to clarify the specific cause and give antipyretic treatment, such as the use of non-steroidal antipyretic drugs for treatment.