A study in Greece found that babies born in winter and autumn had higher birth weight, longer gestational age, and two years longer life expectancy than those born in spring or summer [Flouris et al., 2009]. While the author thought the effect was due to environmental temperature, an earlier study from Australia contradicts the hypothesis. It found no effect in temperature change, but rather an effect in sun exposure during the first trimester, resulting in higher birth weights [Tustin et al., 2004].
In the absence of sunlight, vitamin D supplementation should be encouraged. Bruce Hollis and colleagues recently showed that pregnant women can take 4000 IU/d vitamin D3 with no adverse effects [Hollis et al., 2011]. He recommends 4000 IU/d vitamin D3 during pregnancy and lactation [Hollis and Wagner, 2011].
|Birth weight||3272 g in winter; 3249 g in autumn; 3145 g in spring; 3147 in summer||Flouris, 2009|
|Gestational age||38.87 wks in winter; 38.82 wks in autumn; 38.19 wks in spring and summer||Flouris, 2009|
|Longevity||76.05 yrs in winter; 76.03 yrs in autumn; 73.93 yrs in summer; 73.72 yrs in spring||Flouris, 2009|