Characterization of substance use disorder during pregnancy in a syphilis population

Rates of congenital syphilis and substance use disorder (SUD) have concurrently risen in pregnant patients. Specific substances and their association with inadequately treated syphilis have not yet been identified. The objective of our study was to characterize SUD, including specific drugs of use, among pregnant people with syphilis to determine the association between SUD and adequacy of syphilis treatment.

Patients diagnosed with syphilis during pregnancy between January 1, 2021 and December 31, 2022 were identified. SUD was identified via chart review and confirmed or supported by the use of universal screening for self-reported SUD, ICD-10 codes for mothers and neonates, and toxicology. Maternal demographics and delivery and neonatal outcomes were compared among those with and without SUD. Logistic regression models adjusted for maternal age, Black race, nulliparity, and hypertension were used to produce odds ratios relating SUD to delivery and neonatal outcomes. The timing of penicillin treatment initiation less than 30 days versus 30 or more days before delivery in individuals with and without SUD was compared.

Of 225 patients with syphilis during pregnancy, 40 (17.8%) had SUD. Compared to those without SUD, those diagnosed with SUD were more likely to be Non-Hispanic White with late and limited prenatal care. They were almost six times more likely to have preterm delivery (aOR 5.98 [95% CI 2.47-14.79]) and three times more likely to develop pre-eclampsia with severe features (aOR 3.48 [95% CI 1.41-8.41]). The most common primary drugs of use included non-prescription opioids (32%), methamphetamines (32%), and cannabis (20%). Frequency of syphilis treatment initiation less than 30 days before delivery was higher in individuals with SUD (52% vs. 21%, p = 0.001). Methamphetamine was the most common primary drug of use among patients with SUD who were inadequately treated for syphilis and its rate of use was significantly higher when compared to patients with SUD who were adequately treated (9/21 [43%] vs. 4/19 [21%], p = 0.041).

Pregnant people with SUD, and specifically use of methamphetamines, were more likely to have inadequate syphilis treatment than those without SUD. In addition, demographic and prenatal characteristics differed between individuals with and without SUD, with poorer delivery outcomes observed in patients with SUD and syphilis compared to a syphilis population alone. Future research is needed that addresses the impact of medication-assisted therapies for the treatment of methamphetamine use on rates of adequate syphilis treatment.