The incidence of Jarisch-Herxheimer reactions and associated risk factors in pregnant women and nonpregnant women: A retrospective chart review at a university hospital in Japan.

AIMS: Jarisch-Herxheimer reactions (JHR) is a transient adverse event that occurs during initial antimicrobial treatment for syphilis patients, and is known to develop uterine contractions and fetal distress in pregnant women complicated with syphilis. The aim of this study is to identify risk factors for JHR in patients with syphilis, and to clarify whether pregnancy status is a risk factor for JHR, and to describe the characteristics of pregnant women who develop JHR. METHODS: This was a retrospective chart review in a singleton university hospital in Japan. We collected data of syphilis patients who were diagnosed and treated at department of obstetrics and gynecology, dermatology between January 2010 and May 2022. There were no validated diagnostic criteria for JHR, we defined JHR as one or more of the following in addition to raised body temperature (≧38.0°C) within 24 h of initial antibiotic treatment: headache, chills, myalgias, tachycardia (≧110 bpm), new rash. RESULTS: There were 30 syphilis patients. Of whom nine (30%) were pregnant women and all their neonates were not diagnosed with congenital syphilis. Five patients (17%) developed JHR at the time of initial treatment (JHR group, n = 5). There was no difference between JHR group and non-JHR group (n = 25) in pregnancy status. Secondary syphilis was an only significant risk factor for JHR. Two pregnant women with JHR were both treated for secondary syphilis in the third trimester of pregnancy. CONCLUSION: Pregnancy status was not a risk factor for JHR in syphilis patients. Further research is needed.