Season of birth effects on reproduction

Environmental conditions experienced during foetal and neonatal life influence early development with potential long-term consequences for growth, reproduction, health, and survival. At high latitudes, the external environment varies with the season. This includes factors such as photoperiod, climatic factors, nutrition or prevalence of infectious agents. The seasonal variation of environmental factors may thus influence early pre- and postnatal developmental processes of individuals born at different times of the year, causing potential downstream effects on later life events. Birth season is only one surrogate for the environmental conditions experienced at conception, during pregnancy, around birth and during early postnatal life. There is accumulating evidence that effects of birth season may impact a variety of physical, physiological, and psychological parameters in human populations. The proposed project will focus on one of these parameters, that has been shown to be influenced by birth seasonality and is of particularly high impact in every day life: reproductive performance. Main emphasis will be laid on the question which factors might cause the birth season effects on human reproduction, and whether there are sex differences in the response to environmental conditions during early development. The proposed methodology involves correlational analyses of human data and experimental manipulations of the environmental factors photoperiod and nutrition during early development, using guinea pigs as a model. The proposed project is not only important for a causal understanding of birth season effects on reproduction but may lead to new insights into early causes of subfertility.

Environmental conditions experienced during foetal and neonatal life influence early development with potential long-term consequences for growth, reproduction, health, and survival. At high latitudes, the external environment varies with the season. This includes factors such as photoperiod, climatic factors, nutrition or prevalence of infectious agents. The seasonal variation of environmental factors may thus influence early pre- and postnatal developmental processes of individuals born at different times of the year, causing potential downstream effects on later life events. Birth season is only one surrogate for the environmental conditions experienced at conception, during pregnancy, around birth and during early postnatal life. There is accumulating evidence that effects of birth season may impact a variety of physical, physiological, and psychological parameters in human populations. The proposed project will focus on one of these parameters, that has been shown to be influenced by birth seasonality and is of particularly high impact in every day life: reproductive performance. Main emphasis will be laid on the question which factors might cause the birth season effects on human reproduction, and whether there are sex differences in the response to environmental conditions during early development. The proposed methodology involves correlational analyses of human data and experimental manipulations of the environmental factors photoperiod and nutrition during early development, using guinea pigs as a model. The proposed project is not only important for a causal understanding of birth season effects on reproduction but may lead to new insights into early causes of subfertility.