Season of Birth Effects on Reproduction in Women

Abstract

Environmental conditions experienced during foetal and neonatal life influence early development with potential long-term consequences for later life events. In many parts of the world, the external environment varies with the season. This includes factors such as photoperiod, climatic factors, nutrition or prevalence of infectious agents. Birth season is one surrogate for the environmental conditions experienced at conception, during pregnancy, around birth and during early postnatal life. The seasonal variation of environmental factors may thus influence early pre-and postnatal developmental processes differently in individuals born at different times of the year, causing respective downstream effects on later life events. Accordingly there is accumulating evidence that effects of birth season may impact a variety of physical, physiological and psychological parameters in humans. This review covers a survey of birth season effects on reproductive characteristics in women together with a discussion of possible causes, focussing on environmental factors that might play a central role during development, crucial periods of early development that might be influenced by these environmental factors, and potential underlying physiological mechanisms.

Month of birth and offspring count of women: data from the Southern hemisphere

“…There is accumulating evidence that the seasonal variation of environmental and maternal factors may differently influence pre- and early post-natal developmental processes of individuals born at different times of the year, causing potential down-stream effects on later life events. These effects may impact a variety of physical, physiological, and psychological traits in human populations, such as growth (Weber et al ., 1998), longevity (Doblhammer and Vaupel, 2001; Gavrilov and Gavrilova, 2003; Lerchl, 2004), susceptibility to diseases (Torrey et al ., 1997; Castrogiovanni et al ., 1998; Brenner et al ., 2004), performance (Kihlbom and Johansson, 2004; Fieder et al ., 2006; McGrath et al ., 2006) and reproductive output (reviewed in Huber and Fieder, 2007). The latter has been demonstrated in several historic and modern populations of the Northern hemisphere (Smits et al ., 1997; Lummaa and Tremblay, 2003; Huber et al ., 2004a,b).…”

Strong association between birth month and reproductive performance of Vietnamese women

“…It is increasingly acknowledged that the environmental and maternal conditions during pregnancy and around birth may affect early development, with potential long-lasting effects on later life events. Epidemiological studies on pre-modern and modern Western societies indicate that the birth season may affect a variety of parameters such as reproduction (Huber and Fieder, 2007; Huber et al 2004a,b, 2008; Lummaa and Tremblay, 2003; Smits et al, 1997), growth (Weber et al, 1998), longevity (Doblhammer and Vaupel, 2001; Lerchl, 2004), performance at university and at intelligence tests (Fieder et al, 2006; McGrath et al, 2006), and susceptibility to disease (Castrogiovanni et al, 1998; Mainio et al, 2006; Procopio et al, 2006; Torrey et al, 1997). Studies on the effects of birth season on later life events in developing economies, however, are scarce and nothing is known about the effects of birth season on later reproductive performance.…”

Season of birth influences the timing of first menstruation

“…Birth month is related to the prevalence of obesity (Phillips and Young, 2000;Tanaka et al, 2007), mental health problems (Joiner et al, 2002), diabetes (Fichera et al, 2001), eating disorders (Eagles et al, 2001), breast cancer (Kristoffersen and Hartveit, 2000), allergies (Kusunoki et al, 1999), and premature mortality (Doblhammer and Vaupel, 2001). Epidemiological studies revealed that the month of birth may also affect life expectancy (Doblhammer and Vaupel, 2001;Lerchl, 2004) and parameters related to reproduction, such as mean offspring count (Huber and Fieder, 2007;Lummaa and Tremblay, 2003;Smits et al, 1997) or age at menopause (Cagnacci et al, 2005).…”