Is current therapy for maternal syphilis inadequatefor established fetal infection?

Abstract

There is a growing perception that standard recommended therapy for maternal syphilis does not necessarily cure established diseases in the fetus.1Rawstron SA Bromberg K. Failure of recommended maternal therapy to prevent congenital syphilis.Sex Transm Dis. 1991; 18: 102-106Crossref PubMed Scopus (31) Google Scholar In 1982, 50 of the 159 cases of congenital syphilis reported to the Centers for Disease Control occurred in Texas.2Mascola L Pelosi R Blount JH Binkin NJ Alexander CE Cates W. Congenital syphilis: why is it still occurring?.JAMA. 1984; 252: 1719-1722Crossref PubMed Scopus (57) Google Scholar This series contained the remaining four gravid women who had received the recommended treatment with benzathine penicillin and yet delivered congenitally infected infants. Ricci et al.3Ricci JM Fojaco RM O'Sullivan MJ. Congenital syphilis: the University of Miami/Jackson Memorial Medical Center experience, 1986-1988.Obstet Gynecol. 1989; 74: 687-693PubMed Google Scholar published a series of 56 cases of congenital syphilis. Five gravid women had received benzathine penicillin G (2.4 million units) and two received erythromycin during pregnancy. Wendel et al.4Wendel GD Sanchez P Farris R et al.Treatment of syphilis in pregnancy.in: Proceedings of the Thirty-eighth annual meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 20-23, 1991 Society for Gynecologic Investigation, San Antonio1991Google Scholar reported on the impact of maternal therapy for syphilis during pregnancy. Theirs is one of the few studies in the literature that identified the stage of maternal syphilis. Penicillin G (2.4 million units intramuscularly for 3 weeks) was 100% effective in preventing fetal infection in 100% of patients with primary or late latent syphilis. Among the 75 gravid women with secondary syphilis treated with benzathine penicillin, fetal efficacy was demonstrated in 71 (giving a failure rate of 5.3% for the subgroup). The remaining two failures occurred in gravid women who had early latent syphilis. In this issue of the JOURNAL McFarlin et al.5McFarlin BL Bottoms SF Deck BS Isada NB. Epidemic syphilis: maternal factors associated with congenital infection.AM J OBSTET GYNECOL. 1994; 170: 535-540Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar reported on 16 gravid women who were delivered of congenitally infected infants and had received two doses of benzathine penicillin at weekly intervals during pregnancy. There is not a one-to-one correlation between maternal syphilis and ensuing establishment of fetal infection. According to Stokes the probability of in utero transmission in the live-born progeny of women with untreated syphilis was 40%. Wendel et al.4Wendel GD Sanchez P Farris R et al.Treatment of syphilis in pregnancy.in: Proceedings of the Thirty-eighth annual meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 20-23, 1991 Society for Gynecologic Investigation, San Antonio1991Google Scholar identified a 5.3% incidence of congenital syphilis in the progeny of pregnant women with secondary syphilis, despite maternal therapy that involved three doses of 2.4 million units of benzathine penicillin. By applying the probability of actual fetal infection derived from Stokes (which closely parallels the probability of neurosyphilis in untreated patients) to the series reported by Wendel et al., 30 infants should have had established infection in utero. Of the 30 presumably infected infants, four were considered to have therapeutic failures, which gives a 13% failure rate. Whether the true incidence of fetal therapeutic failures is 5%, 10%, or 13% is an academic point. There is a need for critical reevaluation of therapy of syphilis as it pertains to the pregnant woman with a high probability of established fetal infection.