Is intrauterine growth influenced by the season of birth?

Abstract

It has been established that retarded growth in utero [as assessed through birthweight (BW)] predicts the onset of many chronic diseases in adulthood and affects longevity. The objective of the present study was to examine the hypothesis that intrauterine growth is also influenced by the season of birth. To test our conjecture we used BW and Gestation Age (GA) data from the Birth and Death Registry of Athens. The sample consisted of 516.874 infants (M: 266.579; F: 250.295) bom from 1980 to 2005 in Greece. Males demonstrated greater BW, compared to females [3264.891gr vs. 3137.416gr], Multivariate Analysis of Variance (MANOVA) detected significant effects of both gender and birth quarter on GA and BW. Males bom in the first quarter of the year (Ql) demonstrated significantly greater BW and GA, compared to infants bom in the other quarters of the year [Ql=3283.09gr, 38.56weeks; Q2=3256.91gr, 38.51 weeks; Q3=3258.45gr, 38.48weeks; Q4=3261.1 lgr, 38.48weeks; (pO.OOl)]. Results in females demonstrated a similar significant tendency [Ql=3155.63gr, 38.58weeks; Q2=3127.45gr, 38.52weeks; Q3=3132.17gr, 38.50weeks; Q4=3134.41gr, 38.50weeks; (pO.OOl)]. A chi-square test was then conducted to find in which quarter of the year the lowest number of cases of Low Birth Weight (LBW) infants was observed and found that the lowest number of cases of LBW babies was observed for babies bom in the first quarter of the year, and the highest in the third quarter [Ql=8981; Q2=9748; Q3=10894; Q4=10420; (pO.OOl)]. According to these findings, babies (males & females) bom in the first quarter of the year are significantly heavier, have longer gestation ages and have significantly less risk of being bom with a LBW than babies bom in the other quarters of the year. It is concluded that the season of birth influences significantly BW and WG, possibly due to environmental - climatical conditions, the quality and quantity of nutrition received in utero and also the amount of bright sunshine the pregnant mother is exposed to.