Retrospective analysis of the serologic response to the treatment of syphilis during pregnancy

The purpose of this study was to assess the effect of several maternal variables on the serologic response following the treatment of syphilis in pregnancy.

A 5-year chart review identified 95 patients coded with syphilis at Hermann Hospital. Inclusion criteria were 1) serologically confirmed syphilis infection during the index pregnancy, 2) complete treatment during the index pregnancy, and 3) minimum of one follow-up rapid plasma reagin (RPR) titer. Forty-nine of 95 patients met the inclusion criteria. Treatment response was evaluated by comparing each post-treatment titer of a patient to her pretreatment titer. Each comparison was considered an "observation." Each observation was classified as either a positive response (>/=4-fold titer decline) or a negative response (<4-fold titer decline). Maternal variables assessed included 1) prior history of syphilis untreated or incompletely treated prior to the index pregnancy, 2) gestational age, 3) titer level, 4) unknown duration, 5) positive response at 1 month, 6) positive response at 2 months, 7) positive response at >3 months, and 8) race.

A positive response following treatment was significantly more likely if there was no prior history of syphilis or if there was a high initial RPR titer (>32). Only 33/54 (61%) observations at or greater than 3 months had a positive response.

Our study suggests that an absence of a history of syphilis and an initial high RPR titer are predictive of a positive response following appropriate treatment. Given the low percentage of observations with a positive response at 3 months, we speculate that we may be undertreating our pregnant patients with syphilis infection.