Mode of Delivery and Quarterly Trends in Infant Respiratory Morbidity: Evidence from a Survival Analysis in India

Abstract Background: Acute respiratory infections (ARIs) remain a leading cause of infant morbidity worldwide. While the delivery method has been implicated in early respiratory outcomes, its influence on ARI occurrence across different stages of infancy is less clear. This study aimed to assess the association between delivery method, risk and timing of ARI during the first year of life, with emphasis on quarterly differences in incidence. Materials and Methods: A prospective cohort of 150 infants (30 caesareans and 120 vaginal) in rural Varanasi, India, was followed from birth to 12 months. ARI episodes were assessed quarterly through home visits and analysed using Kaplan–Meier survival curves and Generalised Estimating Equations Poisson regression to explore differences by delivery mode and age quarter. Results: Infants experienced an average of 3.4 ARI episodes in the first year, with incidence highest in the first quarter (0–3 months) and declining in later quarters. Kaplan–Meier analysis showed no significant difference in time to first ARI between caesarean and vaginal deliveries (median: 2 months; P = 0.767). Compared to the 0–3 month reference, the odds of ARI episodes decreased by 41.7% in 4–6 months (odds ratio [OR]: 0.58; 95% confidence interval [CI]: 0.48–0.70), 53.1% in 7–9 months (OR: 0.47; 95% CI: 0.37–0.60) and 40.1% in 10–12 months (OR: 0.60; 95% CI: 0.47–0.76). Conclusion: ARI risk peaked in the first 3 months irrespective of delivery method. Vaginally delivered infants showed a higher incidence at 4–6 months, whereas caesarean-delivered infants tended to have more episodes in later quarters. These quarterly shifts highlight the need for targeted, age-specific prevention strategies.