London: Planning for pregnancy during the summer months may not be a good idea as you may be at an increased risk of developing gestational diabetes, a study says. The study revealed that there can be 51 per cent rise in the incidence of the high blood sugar condition due to a possible peak in the temperature. The study examined seasonal patterns in glucose tolerance and in the diagnosis of gestational diabetes mellitus -- a form of high blood sugar affecting pregnant women. The results indicated that the summer months (June-August) were associated with an increased glucose level and a 51 per cent (or 1.5 times) increased frequency of gestational diabetes compared with the other seasons. "Our findings suggest seasonal variations in the 2-hour glucose concentration and in the proportion of women diagnosed with gestational diabetes with a peak in the summer," said Anastasia Katsarou from Lund University in Sweden. The temperature-induced changes in peripheral blood flow may affect the composition of capillary blood, representing a mixture of arterial and venous blood and thus increase glucose levels during the warmer summer months, Katsarou explained. For the study, a total of 11,538 women underwent a universally applied standard 75-g oral glucose tolerance test (OGTT) in the 28th-week of pregnancy during 2003-2005 in southern Sweden. The OGTT results from the 3-year study period were grouped together into months and seasons. Out of these, a total of 487 women (4.2 per cent) were diagnosed with gestational diabetes during the study period. The monthly frequency of gestational diabetes ranged from 2.9 per cent in March to 5.8 per cent in June. The seasonal frequency ranged from 3.3 per cent in spring to 5.5 per cent in summer. The differences were statistically significant for both month and season. Mean monthly temperature ranged from -0.6 degree C in the winter to 17.7 degree C in the summer, the study said. Further analysis showed that the 2-hour glucose level increased by 0.009 mmol/L for every degree increase in temperature and this corresponded in a difference of 0.15 mmol/L between winter and summer. However, these associations were no longer apparent when also adjusting for mean monthly temperature, suggesting that temperature could be part of the reason for the differences. The study was recently presented at 2016 European Association for the Study of Diabetes (EASD) meeting in Munich, Germany.