Obstetric and neonatal risks of Streptococcus agalactiae in adolescent pregnancy: a retrospective matched cohort study.

Objectives: Streptococcus agalactiae (GBS) infection is significant in obstetric and neonatal complications. Maternal age, particularly adolescent pregnancy, may influence the prevalence of GBS colonization and associated clinical outcomes. This study aimed to evaluate the impact of maternal age on obstetric and neonatal outcomes, with a specific focus on the modifying effect of GBS status. The analysis explored whether the associations between maternal age and selected outcomes remained statistically significant after adjusting for GBS interactions.

Material and methods: A retrospective matched cohort study was conducted with 582 participants, comprising a study group and a matched control group selected through propensity score matching. The study group included adolescents (≤ 19 years, n = 194) and older individuals (> 19 years, n = 388). Inclusion criteria required GBS screening after the 35th week of gestation, bacterial culture upon hospital admission, and delivery during the same hospitalization. Statistical analyses included logistic and linear regression models adjusted for interactions with GBS.

Results: In unadjusted analyses, adolescent mothers showed a higher likelihood of postpartum hemorrhage (OR = 2.715, p = 0.02), uterine atony (OR = 3.594, p = 0.043), transient tachypnea of the newborn (TTN) (OR = 6.16, p = 0.027), and shorter neonatal length (Estimation = -0.791, p = 0.001). However, after adjusting for interactions with GBS, these associations lost statistical significance: postpartum hemorrhage (AOR = 0.67, p = 0.711), uterine atony (AOR = 2.417, p = 0.315), TTN (AOR = 4.87, p = 0.117), and neonatal length (Estimation = -0.207, p = 0.584).

Conclusions: These findings indicate that GBS colonization confounds the observed relationships between maternal age and these outcomes. These results underscore the importance of accounting for GBS status in assessing age-related risks during pregnancy and tailoring clinical management accordingly.