Maternal exposure to first‐trimester sunshine is associated with increased birth weight in human infants

Abstract

Two alternative hypotheses have been generated to account for seasonal variation in the birth weight of human infants born in industrialized countries. First, it has been hypothesized that low ambient temperature during the second trimester of gestation decreases birth weight. Second, it has been hypothesized that exposure to bright sunshine during the first trimester increases birth weight. We tested these two hypotheses to determine which, if either, accounted for seasonal variation in birth weight of full-term infants. Birth weight data, collected over a 5-year period, were analyzed as a function of peak and trough sunshine and ambient temperature. Although there was no effect of ambient temperature during any trimester on birth weight, infants whose mothers were exposed to peak sunshine during their first trimester were born significantly heavier than infants whose mothers experienced trough levels of sunshine during the same trimester. Furthermore, infants whose mothers were exposed to trough levels of sunshine during their second and third trimesters were born significantly heavier than infants whose mothers were exposed to peak levels of sunshine during the same trimesters. We hypothesize that high levels of sunshine during early gestation may increase the level of insulin-like growth factor (IGF)-1, facilitating prenatal growth.

The association between birth weight, season of birth and latitude

“…summer) were significantly heavier compared to those who had their first trimester during the months of lowest sunshine (i.e. winter) (Tustin et al 2004). In a sample from Northern Ireland (Murray et al 2000), significant seasonal fluctuations in birth weight were found in singletons born after at least 36 weeks of gestation (n ¼ 418 817).…”

Season of birth is associated with anthropometric and neurocognitive outcomes during infancy and childhood in a general population birth cohort

“…Compared to summer and autumn babies, those born in winter and spring tend to be heavier (Selvin and Janerich, 1971;Roberts, 1975;Matsuda et al, 1993;Murray et al, 2000;Waldie et al, 2000;Tustin et al, 2004;McGrath et al, 2005, in press) and longer (Wohlfahrt et al, 1998;Waldie et al, 2000;McGrath et al, 2005). These small anthropometric differences persist into adulthood: at age 18 winter/spring born individuals are taller compared to summer/autumn born individuals (Weber et al, 1998;Waldie et al, 2000).…”

Seasonal variation in birth weight

“…2 It is important to point out that the 299-g difference in birth weight between the infants with deficient and adequate vitamin D status in our study is 10 times greater than the weight difference that would be expected because of seasonal effects alone in industrialized countries. 2 In the Winnipeg cohort, vitamin D status was highest in infants born in the summer (although season did not contribute to the regression analysis for bone mineral content in our study), but body weight did not follow the same pattern (Fig. 1).…”

“…2 The spring-born infants (n = 14) tended to weigh the most (difference of 244 g, p = 0.08, t test). These infants would have been conceived in the peak period of sunshine and warm temperatures in Winnipeg.…”

“…In particular, visceral adiposity is highly correlated with NAFLD, whereas the correlation with subcutaneous obesity is weaker. 2 Intra-abdominal fat delivers fatty acids directly into the portal vein, promoting insulin resistance. 2 Patients with truncal obesity have very low levels of adiponectin and high levels of tumour necrosis factor-α (TNF-α).…”