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Temporal and seasonal variations in incidence of stage II and III NEC—a 28-year epidemiologic study from tertiary NICUs in Connecticut, USA



To investigate seasonality and temporal trends in the incidence of NEC.

Study design

A retrospective cohort study from two tertiary NICUs in northern and central Connecticut involving 16,761 infants admitted over a 28-year period. Various perinatal and neonatal risk factors were evaluated by univariate, multivariate, and spectral density analyses.


Incidence of NEC was unchanged over the 28 years of study. Gestational age, birth weight, and birth-months (birth in April/May) were independently associated with stage II or III NEC even after adjusting for confounding factors (p < 0.05). Yearly NEC incidence showed a multi-modal distribution with spectral density spikes approximately every 10 years.


Temporal and seasonal factors may play a role in NEC with a peak incidence in infants born in April/May and periodicity spikes approximately every 10 years. These trends suggest non-random and possibly environmental factors influencing NEC.

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Fig. 1: Incidence of NEC by year of birth.
Fig. 2: Power spectrum density (PSD) of the percentage incidence of NEC done by using the signal.periodogram function in the Scipy toolbox.
Fig. 3: Incidence of NEC by the month of birth—all admissions to the NICU.
Fig. 4: Incidence of NEC by the month of birth—infants <29 weeks gestational age at birth.
Fig. 5: Incidence of NEC by the month of birth—infants ≥29 weeks gestational age at birth.


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The authors would like to acknowledge the support of the University of Connecticut, UConn Health, and Connecticut Children’s Medical Center in this project. Specifically, we would like to acknowledge the support of UConn-Office of Undergraduate Research that provided a student research grant for DJ.


Funding for this project was partially provided by a UConn Health Research Program grant for DJ through the Office of Undergraduate Research.

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DJ aggregated and organized the patient data, performed the statistical analysis, and prepared the manuscript. ZW performed the spectrum analysis and assisted in statistical analysis. SR supervised and mentored the contributions of ZW. NH conceptualized this project, designed the study, and supervised DJ in the data aggregation and analysis. He also mentored DJ in writing and editing the manuscript.

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Correspondence to Naveed Hussain.

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Javidi, D., Wang, Z., Rajasekaran, S. et al. Temporal and seasonal variations in incidence of stage II and III NEC—a 28-year epidemiologic study from tertiary NICUs in Connecticut, USA. J Perinatol 41, 1100–1109 (2021).

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