(965) Impact of maternal substance use on infant birth weight and congenital syphilis outcomes

Evaluate the impact of maternal substance on congenital syphilis outcomes.

Study Design:

This is a retrospective cohort study of pregnant patients with syphilis who delivered at a large, public hospital. We excluded individuals with syphilis treatment prior to pregnancy except in cases of early syphilis. We reviewed medical records for demographics, comorbidities, substances used, STI coinfections, syphilis staging and neonatal outcomes. Maternal substance use was documented in the medical record based on self-report or indicated maternal urine toxicology testing during pregnancy or delivery. We evaluated the impact of maternal substance use on syphilis-associated neonatal outcomes and infant birth weight.

Results:

From January 1, 2010 through June 30, 2025, 581 pregnant patients with syphilis were included, of whom 166 (29%) reported substance use during pregnancy (tobacco [58%], cannabis [54%], methamphetamines [37%], opioids [28%], cocaine [16%] and alcohol [11%]). Compared to patients without substance use, those with substance use were older (27.1 vs. 24.9 years, p< 0.001) had higher chronic (13% vs. 5%, p=0.002) and pregnancy-induced hypertension (40% vs. 26%, p< 0.001), and fewer prenatal visits (median 5 vs. 10 , p< 0.001). Syphilis was also diagnosed later (24 vs. 17 weeks, p< 0.001), with initial RPR ≥1:16 more commonly (67% vs. 57%, p=0.026), and less frequent treatment before delivery (73% vs. 93%, p< 0.001). Infant birth weight and gestational age at delivery were lower among those with substance use; small for gestational age was more frequent (14 vs 8%, p < 0.001). Congenital syphilis was more frequent among substance-exposed neonates (33[20%] vs. 49[12%], OR 1.83, 95%CI, 1.10-3.02).

Conclusion:

Maternal substance use in pregnancies affected by syphilis was associated with delayed prenatal care, less adequate treatment, and worse neonatal outcomes, including congenital syphilis, and lower birth weight. Fetal growth concerns in syphilis-exposed infants may be secondary to superimposed maternal substance use and earlier delivery.