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Higher solar UVB during first trimester of pregnancy associated with better fetal development

Posted on: November 10, 2011   by  Dr William Grant


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 weight3272 g in winter; 3249 g in autumn; 3145 g in spring; 3147 in summerFlouris, 2009
Gestational age38.87 wks in winter; 38.82 wks in autumn; 38.19 wks in spring and summerFlouris, 2009
Longevity76.05 yrs in winter; 76.03 yrs in autumn; 73.93 yrs in summer; 73.72 yrs in springFlouris, 2009


  1. Flouris AD, Spiropoulos Y, Sakellariou GJ, Koutedakis Y. Effect of seasonal programming on fetal development and longevity: links with environmental temperature. Am J Hum Biol. 2009 Mar-Apr;21(2):214-6.
  2. Hollis BW, Johnson D, Hulsey TC, Ebeling M, Wagner CL. Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness. J Bone Miner Res. 2011 Oct;26(10):2341-57.
  3. Hollis BW, Wagner CL. Vitamin D requirements and supplementation during pregnancy. Curr Opin Endocrinol Diabetes Obes. 2011 Dec;18(6):371-5.
  4. Tustin K, Gross J, Hayne H. Maternal exposure to first-trimester sunshine is associated with increased birth weight in human infants. Dev Psychobiol. 2004 Dec;45(4):221-30.

1 Response to Higher solar UVB during first trimester of pregnancy associated with better fetal development

  1. [email protected]

    very interesting – thanki you Bill, Oliver Gillie

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