Do women with persistently negative nontreponemal test results transmit syphilis during pregnancy?

Syphilis screening algorithms have been reversed to take advantage of new automated treponemal tests. Screening that begins with a treponemal test identifies persons with positive treponemal and negative nontreponemal test results who were missed when screening began with a nontreponemal test. The significance of these results is uncertain. We wondered if mothers with persistently negative nontreponemal test results could transmit syphilis to their newborns.

We reviewed congenital syphilis cases reported to the Centers for Disease Control and Prevention to identify all instances where (1) the mother had persistently negative nontreponemal test results (best evidence would be multiple negative nontreponemal test results with at least one >30 days after birth) and (2) the child had evidence of infection (best evidence a confirmed case, older child, stillbirth, or "probable" by the criteria of Kaufman et al.).

A total of 23,863 patients with congenital syphilis had birthdates between 1991 and 2009. Of 106 mothers initially classified as having only negative nontreponemal test results reported, 20 were misclassified; the remaining 86 mothers had no infants with confirmed syphilis and no syphilitic stillbirths. The 23,757 other mothers had 284 (1.2%) infants with confirmed syphilis and 1271 (5.4%) syphilitic stillbirths. Twelve of the 86 mothers had negative nontreponemal test results more than 30 days after delivery; none of their children had convincing evidence of infection. One mother had a negative nontreponemal test result 27 days after delivery of a child with "positive x-rays" and elevated cerebrospinal fluid cell count or protein, but details were unavailable. Fifty-nine children were diagnosed at age 1 year or older; nontreponemal test results were available for 13 of the mothers, and all were positive.

We found no convincing evidence of syphilis transmission from mothers with persistently negative nontreponemal test results. Only 1 case suggested that transmission may have occurred, and records were incomplete.