This analysis of California STI surveillance data aimed to determine whether infants born to birthing parents with syphilis of late/unknown duration treated with 3 weekly doses of benzathine penicillin G (BPGx3) administered at 6-8 day intervals (initiated ≥ 30 days before delivery) would be more likely to meet congenital syphilis (CS) criteria than infants born to parents who received BPGx3 at strict 7-day intervals.  CS cases were defined using a combination of surveillance and clinical criteria.  Between January 2016 and June 2019, 1,092 parent-infant dyads were eligible for analysis.  607 parents (55.6%) received BPGx3 at strict 7-day intervals, 70 (6.4%) received treatment at 6-8 day intervals, and 415 (38%) received no or inadequate treatment.  There were no significant differences between parents receiving 7 vs. 6-8 day interval BPGx3 with regard to age, race/ethnicity, HIV status, receipt of prenatal care, trimester for establishing prenatal care, and highest non-treponemal titers in pregnancy.  Parents who received no/inadequate treatment were less likely to have received prenatal care and were diagnosed with syphilis later in pregnancy, and almost 60% had not received any treatment prior to delivery.  CS incidence proportions in the 7, 6-8 day, and no/inadequate treatment groups were 5.6%, 5.7%, and 36.9% respectively: there was no difference in CS incidence between the first two groups.