Modeling seasonality in fecundability, conceptions, and births

Area of Science:

• Demography
• Reproductive Epidemiology
• Biostatistics

Background:

• Understanding seasonal variations in human reproduction is crucial for public health and demographic studies.
• Existing models often lack comprehensive integration of individual-level behavioral and biological factors influencing fecundability.
• Population-level birth seasonality is influenced by fluctuating susceptible populations and environmental factors.

Purpose of the Study:

• To develop a comprehensive model of seasonal fluctuations in fecundability, conceptions, and births.
• To integrate individual-level determinants of fecundability (behavioral and biological) into a population-level seasonal model.
• To analyze specific hypotheses, such as the impact of extreme summer heat, on birth seasonality.

Main Methods:

• Development of an individual-level fecundability model incorporating coital frequency, sperm concentration, fetal loss, and contraception.
• Expansion of the individual model to a population-level model accounting for seasonal changes in the susceptible population size.
• Application of the model to investigate proposed explanations for birth seasonality, including extreme heat effects.

Main Results:

• The developed model provides a framework for understanding the interplay of individual and population factors in seasonal birth patterns.
• The model allows for the quantitative assessment of various hypotheses explaining birth seasonality.
• Analysis using the model can help elucidate the role of environmental factors like heat in reproductive timing.

Conclusions:

• A unified model effectively captures seasonal fluctuations in fecundability, conceptions, and births.
• The model highlights the importance of considering both individual fertility dynamics and population-level variations.
• Further research can utilize this model to explore diverse environmental and behavioral influences on reproductive seasonality.