Birth Outcomes Among Women With Syphilis During Pregnancy in Six U.S. States, 2018-2021

To describe the association between syphilis treatment status and adverse pregnancy and neonatal outcomes among pregnancies complicated by syphilis.

Six jurisdictions that participated in SET-NET (Surveillance for Emerging Threats to Mothers and Babies Network) reported data on women with syphilis during pregnancy and outcomes that occurred during 2018-2021. Frequencies of adverse outcomes were reported by syphilis treatment status during pregnancy as defined by the 2021 Sexually Transmitted Infections Treatment Guidelines (inadequate, adequate, and no treatment). Adjusted risk ratios (aRRs) were modeled for each outcome comparing adequate treatment with no treatment and with inadequate treatment, controlling for the pregnant woman's age at infection, education level, insurance status, reported substance use, number of prenatal visits, and stage of syphilis.

As of June 7, 2024, 1,682 singleton pregnancies complicated by syphilis were reported, with more than half of pregnant women adequately treated for syphilis (57.6%). Pregnant women with no or inadequate treatment had higher relative frequencies of adverse outcomes (stillbirth, prematurity, low birth weight [LBW], and neonatal intensive care unit [NICU] admission) than those with adequate treatment. The aRRs for stillbirth (9.9% vs 1.4%, aRR 3.72, 95% CI, 1.73-8.03), LBW (30.1% vs 9.9%, aRR 1.51, 95% CI, 1.07-2.14), and NICU admission (66.7% vs 27.0%, aRR 1.60, 95% CI, 1.28-1.98) were higher in pregnant women with no treatment compared with those with adequate treatment. Inadequate treatment was associated with LBW and NICU admission (24.9% vs 9.9%, aRR 1.81, 95% CI, 1.29-2.52; and 57.2% vs 27.0%, aRR 1.61, 95% CI, 1.31-1.99, respectively) compared with adequate treatment.

The high relative frequencies of adverse pregnancy and neonatal outcomes associated with inadequately treated or untreated syphilis during pregnancy reinforce the importance of adequate treatment in mitigating the effects of syphilitic infection. Increased attention and systematic strategies are needed to address gaps in screening and treatment before and during pregnancy to reduce adverse pregnancy and neonatal outcomes.