Serological changes for syphilis in infants born to treated syphilitic mothers

Objective To explore the serological variations for syphilis in infants delivered by treated syphilitic mothers and its influencing factors. Methods Totally, 146 singleton gravidas, who had been treated for syphilis during pregrancy from January 2006 to January 2008 in our hospital, were chosen. Rapid plasma reagin(RPR) and treponema pallidum particle agglutination assay (TPPA) of these mothers before delivery and of the newborns within 3 d after delivery were tested and 92 of the 146 babies were followed up until the age of 24 months. Results (1) Among the 146 neonates, 104 (71.2%) were positive for both RPR and TPPA and 140 (95.9%) TPPA positive only. The RPR positive rate in neonates born to RPR+ + TPPA+ mothers were higher than those born to TPPA+ (only) mothers (81.4% vs 36.4%,χ2 = 25. 3, P 1 [(2.5±0.8) mo vs (1. 2±0. 4) mo,P 0.05). The seroreversion time of RPR in infants with neonatal RPR titer of 1 : 4 was later than those with neonatal RPR titer of 1:1 [(3.7±0. 9) mo vs (2. 3±0. 6) mo,P<0. 01], and babies with RPR titer at 1 : 1 - 1 :4 showed longer duration than those with neonatal RPR- in TPPA seroreversion [(11. 2±2. 8) mo, (12.2±2.9) mo, and (11.0±2.2) mo vs ( 6. 9±2. 1) mo, P< 0.01, respectively]. Conclusions Most infants born to syphilitic mothers are serological positive for syphilis despite of standard maternal treatment during pregnancy. Infants, with higher maternal RPR titer during the pregnancy or at delivery, may persist to be serological positive for syphilis for a longer perieod, but all will turn to negative finally. Long term follow up is recommended for serological positive infants, and the diagnosis of congenital syphilis should be cautious. Key words: Pregnancy complications, infectious;  Syphilis;  Infant, newborn;  Reagins;  Syphilis serodiagnosis