241 - Season of conception and risk of bronchopulmonary dysplasia in singleton preterm infants < 30 weeks gestation: a retrospective cohort study

Publication Number: 241.6345

Smita Roychoudhury, McMaster University, Hamilton, ON, Canada; Selphee Tang, Alberta Health Services, Calgary, AB, Canada; Shabih U. Hasan, University of Calgary, Calgary, AB, Canada; Belal Alshaikh, University of Calgary, Calgary, AB, Canada; Kamran Yusuf, (403) 210 3930, Calgary, AB, Canada

Background: Environmental exposures such as infections and maternal vitamin D levels follow seasonal patterns and affect fetal development especially lung development. Respiratory problems are more common in children conceived in winter months. The effect of season of conception on bronchopulmonary dysplasia (BPD) is unknown.

Objective: To assess impact of season of conception on the incidence of BPD in singleton preterm infants < 30 weeks gestation

Design/Methods: Retrospective cohort study of infants < 30 weeks gestation born between January 2004 and December 2018 at a tertiary level NICU. Exclusion criteria included moribund infants and major congenital anomalies. Conception date was calculated as date of birth minus gestational age plus 14 days, and then divided into winter months (November - February) and non-winter months. The primary outcome was BPD, defined as any respiratory support at 36 weeks postmenstrual age. Secondary outcomes included death, retinopathy of prematurity (ROP) > stage 3, necrotizing enterocolitis (NEC) ≥ stage 2 and intraventricular hemorrhage (IVH), periventricular leucomalacia (PVL) and death. Multivariate logistic regression analysis was used to assess the effect of confounders

Results: The figure shows the flow diagram of the study cohort. Of the 881 infants eligible, 287 were conceived in winter (32.5%). Table 1 shows the maternal and neonatal characteristics. Results of logistic regression are shown in Table 2.. The adjusted odd ratios for BPD was significantly higher in the winter group (1.91 95% CI 1.39-2.63) (adjusted for season, maternal body mass index ≥ 30, sex, maternal smoking, pregnancy induced hypertension, small for gestational age, antenatal steroids, gestational age. These variables were chosen for the model as they are not involved in the causal pathway. Two other regression model were also evaluated with similar results).There was no difference in any of the secondary outcomes between the two groups.

Conclusion(s): Singleton infants < 30 weeks gestation conceived in winter months have a higher incidence of BPD. Our results are consistent with the seasonal variation of increased infections and reduced ultraviolet exposure in the first trimester. Although our results may be of importance for public health, they need validation in larger and different cohorts.

Table 1. MATERNAL AND NAONATAL CHARACTERISTICS
*Chi-square or Fisher’s exact test for categorical variables t-test or Mann-Whitney U test for continuous variables
SGA= Small for gestational age, PDA=patent ductus arteriosus, NEC= necrotizing enterocolitis, IVH=intraventricular hemorrhage, ROP=retinopathy of prematurity


Table 2. LOGISTIC REGRESSION FOR THE PRIMARY AND SECONDARY OUTCOMES
Adjusted for season, maternal body mass index ≥ 30, sex, maternal smoking, pregnancy induced hypertension, small for gestational age, antenatal steroids, gestational age.

Figure. FLOW DIAGRAM OF THE STUDY COHORT