Fevers During Pregnancy By Lara A Friel, MD, PhD, University of Texas Health Medical School at Houston, McGovern Medical School Reviewed / Revised Oct 2021 | Modified Sep 2022 View Patient Education A temperature of > 39.5 ° C (> 103 ° F) during the 1st trimester increases risk of Spontaneous abortion Fetal brain or spinal cord defects Fever late in pregnancy increases risk of Preterm labor Treatment of fever is directed at the cause, but antipyretics are indicated to decrease maternal temperature.