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

Abstract

This study provides evidence for a causal link between the seasonality of the environment during the pre- and perinatal period and offspring count of women. It further indicates that the main contribution of the birth month effect found in the present study comes from the lowest family income category.

Perinatal winter conditions affect later reproductive performance in romanian women: Intra and intergenerational effects

“…We find a strong association between birth month and later offspring count in Romanian women: on average, women born in winter months have the fewest and those born in summer the most offspring. This is in contrast to our findings from contemporary Austria and New Zealand, where the average number of children was lowest among women born in summer months (Huber et al, 2004(Huber et al, , 2008. Even though the present data would support scenarios such as that spring conditions around conception and during early gestation might be detrimental to later reproduction of Romanian women, coincidence between decreased reproductive success and low ambient temperature around birth rather points to a detrimental effect of winter conditions during the perinatal period.…”

“…Correspondingly, in this study, the association between birth month and later offspring number is only significant among the lower educated but not the higher educated Romanian women. A similar effect of education and income, respectively, on the association between birth month and later reproduction has been reported on New Zealand and Vietnamese women: likewise the association was significant only in the poorer, lower educated women (Huber and Fieder, 2009;Huber et al, 2008). In Austria and New Zealand, where overall socio-economic standards are much higher than in Romania, then maybe more subtle effects of perinatal summer conditions (or early prenatal winter conditions) on later reproductive performance have appeared.…”

“…The month of birth may thus be associated with various physical, physiological, and psychological traits (e.g., Doblhammer and Vaupel, 2001;Fieder et al, 2006;Weber et al, 1998), and also reproductive performance (Huber et al, 2004;Lummaa and Tremblay, 2003). In women, several studies demonstrated lower average reproductive performance after birth in summer months, both in the Northern and the Southern hemisphere (Huber et al, 2004(Huber et al, , 2008Lummaa and Tremblay, 2003;Smits et al, 1997).…”

Modeling month‐season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis

“…M-SOB has been reported to be a risk factor in susceptibility to a variety of chronic human disease (1-22), including MS (25)(26)(27)(28)(29)(30). A recent study has indicated that the M-SOB effect in MS susceptibility correlates with M-SOB effects on birth rates, with the lowest and greatest risk of developing MS coinciding with the M-SOB that exhibits the lowest and highest birth rates, respectively (38).…”

“…With respect to inflammatory neurologic disorders, numerous groups have identified M-SOB as a risk factor in multiple sclerosis (MS) (25)(26)(27)(28)(29)(30). This is thought to be primarily a function of seasonal changes in developmental exposure to sunlight and/or vitamin D (VitD) status (31)(32)(33)(34); however, it has been suggested that the relationship between MS susceptibility and M-SOB may be spurious because several studies may not have adequately controlled for confounders, such as patterns of live births in the general population, year of birth, latitude, and region (35)(36)(37).…”