Contribution of syphilis to adverse pregnancy outcomes in people living with and without HIV in south Brazil: 2008-2018.

BACKGROUND: Syphilis co-infection among pregnant people living with HIV (PLH) may worsen pregnancy outcomes. We evaluated the impact of syphilis co-infection on pregnancies in south Brazil.

METHODS: Data was extracted from hospital records between 1/1/2008 -12/31/2018. Preterm birth (PTB), low birth weight (LBW < 2500 g), and a composite adverse infant outcome [AIO: HIV vertical transmission, loss to follow-up before HIV diagnosis (LTFU), stillbirth, congenital syphilis] were evaluated among pregnancies without HIV and syphilis (PWOH+S), PLH mono-infection, syphilis mono-infection (PLS), and PLH with syphilis (PLH + S).

RESULTS: Among 48,685 deliveries where patients were tested for HIV and syphilis, 1,353 (2.8%) occurred in PLH; of these, 181 (13.4%) were HIV/syphilis co-infected (PLH + S). Among PLH, 2.4% of infants acquired HIV and 13.1% were LTFU. Among all PLS, 70.5% of infants acquired congenital syphilis. Across the cohort, 1.2% stillbirths/neonatal deaths occurred. 37.0% of PLH + S did not initiate ART versus 15.4% of PLH mono-infection (p < 0.001). 37.6% of PLH + S had VDRL titers >1:16 compared to 21.7% of PLS only (p < 0.001). Among PLH, syphilis co-infection and unknown/high VDRL titers (>1:16) increased AIO risk more (aRR:3.96, 95%CI:3.33-4.70) compared to low VDRL titers (<1:8) (aRR:3.51, 95%CI:2.90-4.25). Unsuppressed viremia (>50 copies/mL) was associated with risk of PTB (aRR:1.43, 95%CI:1.07-1.92) and AIO (aRR:1.38, 95%CI:1.11-1.70) but not LBW. Lack of prenatal care was significant in predicting PTB and LBW in all PLH and PLS mono-infection.

CONCLUSION: Syphilis co-infection worsens adverse infant outcomes in all women and compounds negative effects of HIV infection during pregnancy. Effective syphilis treatment and HIV VL suppression are paramount for optimal obstetric care.