In many geographical regions, syphilis is still the most common cause of fetal death in the later months of gestation. In many developed countries, the number of primary and secondary syphilis cases rose dramatically during the late 1980s and early 1990s (peak 1991) as a result of illicit drug use and the exchange of drugs for sex. Although rare in developed countries, the incidence of syphilis is high and increasing in many developing countries (and in the transitional economies of Eastern Europe and the former Soviet Union), particularly where HIV/AIDS is common. Of infants born to mothers with primary or secondary syphilis, up to 50% will be premature, stillborn, or die in the neonatal period. In many cases, surviving children are born with congenital defects some of which may not be apparent for years.
The fetus is infected through the placenta from the mother. When an infected fetus is born alive, the symptomatology of congenital syphilis soon becomes manifest. While appropriate treatment of the mother can prevent congenital syphilis, the inability to effectively identify infected patients and get them to undergo treatment continues to present a challenge to reducing the incidence of syphilitic complications. Screening in the ﬁrst trimester with nontreponemal tests such as rapid plasma reagin or Venereal Disease Research Laboratory test combined with conﬁrmation of reactive individuals with treponemal tests such as the ﬂuorescent treponemal antibody absorption (FTA-ABS) assay is a cost-effective strategy. Those at risk should be retested in the third trimester.
A syphilitic fetus, born in the fetal stage by abortion or later as a mature infant, is usually shorter than expected or otherwise growth restricted. When delivered alive or shortly after death in utero, the skin appears dry, brittle, and sometimes a lusterless gray. In various body regions vesicles may be found. Rapid mac- eration, however, takes place when, as happens frequently, the fetus dies and remains in the uterus for a period of time, which may vary greatly. These external lesions should always prompt an autopsy, which will ascertain the diagnosis by the characteristic changes detectable in the internal organs. Inﬂammatory and degenerative changes are usually present in the liver, lungs, spleen, kidneys, and pancreas. Most characteristic are the bone changes, where the ﬁnding of an osteo- chondritis, with signs of disturbed ossiﬁcation and deranged cartilage tissue, is considered pathognomonic. Efforts to demonstrate Treponema pallidum (Spirochaeta pallida) in the internal organs or bone are seldom successful in fetuses aborted during the ﬁrst half of pregnancy. In later stages, particularly when the fetus is partially autolyzed, the viscera are usually ﬂooded with organisms.
No part of the placenta or fetal membranes seems to be impervious to the invasion of the Treponema pallidum. In untreated cases the placenta is enlarged, excessively lobulated, pale, and edematous. The cord and membranes show discoloration and other postmortem changes comparable to those in the macerated fetus. Microscopically, one ﬁnds diffuse inﬂammation of the placenta, increased ﬁbrous stroma in the bloodless villi, and marked proliferation of the intima in the fetal vessels. Although these lesions are characteristic of syphilis, the only conclusive proof of the disease is the ﬁnding of the Treponema in the tissues (Levaditi stain or dark-ﬁeld examination).
Prenatal care, compulsory serologic examination of all pregnant women, and penicillin therapy during each succeeding pregnancy, whenever syphilitic infection appears in the history of the woman even though the serology may remain negative after the ﬁrst course of treatment, are the measures, which have decreased tremendously the incidence of congenital syphilis. In determining appropriate therapy, the stage of maternal infection, the length of fetal exposure, and physiologic changes in pregnancy that can affect the pharmacokinetics of antibiotics must all be considered. These decisions may be further complicated by allergy to penicillin or immunocompromise (HIV). Even with appropriate treatment, fetal infection may still occur in up to 14% of cases.