The impact of COVID-19 and influenza on the development of obstetric complications and pregnancy outcomes

The decline in the birth rate recorded in Russia in the early 2000s exacerbated depopulation trends. Since 1993, the country has experienced a steady natural population decline due to a combination of socioeconomic factors and pregnancy complications. Transient immunosuppression during pregnancy increases women’s susceptibility to infections, the most significant of which are influenza and COVID-19. Objective. To assess the impact of viral diseases—influenza and COVID-19—on pregnancy outcomes, as well as the incidence of obstetric complications in pregnant women who had influenza or COVID-19, using Penza as an example. Materials and methods. A retrospective analysis of the medical records of 1.754 pregnant women in Penza from 2020 to 2025 was conducted. Two observation groups were formed: the study group (n=877) with laboratory-confirmed COVID-19 or influenza, and the control group (n=877) without infectious diseases. The control group was matched by paired matching based on age, gestational age, and parity. Results. The groups were comparable in baseline characteristics (p>0.05). Infectious diseases significantly increase the odds of developing pregnancy complications (odds ratio 5.66; 95% confidence interval 3.92—8.18). Influenza is associated with a higher risk of complications than COVID-19: general complications were 3.84 times more common (95% CI 2.26—6.49), preterm birth was 3.84 times more common (95% CI 2.18—6.70), and the risk of early reproductive loss was 3.81 times higher (95% CI 1.21—10.20). Conclusion. Influenza during pregnancy poses a greater risk to pregnancy than COVID-19, increasing the risk of complications by 3.8—5.7 times. The most severe complication is preterm birth. These data support the need for further research to evaluate the effectiveness of influenza vaccination as a potential method for reducing the incidence of obstetric complications.