I consulted M. Paul's book: Occupational and Environmental Reproductive Hazards. She says that when maternal core temps reach 102 degrees F. (38.9 C. or greater) there have been reports of abnormal fetal development. Fevers this high occurring during the period of neural tube closure (days 20 to 28 after conception)have been associated with a significantly increased incidence of central nervous system related defects.

Studies of influenza epidemics in Europe in the 1950s and 1960s reveal a 2-3 fold increase in congenital anomalies among infants born to women with sustained fever episodes in the 1st trimester. No infants exposed to high temps after 16 weeks gestation (18 wk by LMP) had malformations. There were no stillborn or premature births reported. All fevers were above 102 degrees and these were sustained for 1 or more days.

In another study, no association was found between febrile episodes and incidence of birth defects or problems with the pregnancy. "Other prospective and retrospective studies failed to find a significant association between hyperthermia due to influenza in early pregnancy and abnormal pregnancy outcomes" (M. Paul).

At 28 weeks, you are beyond the sensitive period anyway, so I would feel confident that no harm has been done.

Fever can safely be lowered in pregnancy through the use of tylenol or tepid baths.