Introduction: GDM seasonability has been rarely addressed, with conflicting results. The aim of the study is to evaluate monthly GDM incidence in a large group of Greek women.
Methods: 7618 pregnant women underwent 100g OGTT during the third trimester (GDM: ADA 2000 criteria). Seasonal, monthly GDM incidences and mean seasonal glucose levels during OGTT were calculated. Mean month temperature data were obtained from the Greek Meteorological Service.
Results: GDM incidence, relative prevalence (RP), odds ratio (OR95% CI) and mean temperature per month as in Table 1.
Seasonal GDM incidence was significantly different: Winter (W)=28.1%, Summer (S)=39.2%, Spring (Spr)=32.4% and Autumn (A)=32.4% (×2=51.0, P<0.0001). Glucose levels (Glu) during OGTT were calculated. There was no statistical difference in fasting glucose blood levels. On the contrary, significantly increased blood glucose values were observed at 60, 120 and 180 in S vs W, while Spr and A values were intermediate (ANOVA: P<0.0001). Glu60 (mg/dl): W=163±42, Spr=166±42, A=167±39, S=173±40, Glu120: W=137±41, Spr=138±41, A=139±38, S=146±40, Glu180:W=109±33, Spr=110±33, A=111±32 S=116±34.
The effect of season on postload glucose levels remained an independent significant factor after adjustment for age, gestational age, BMI, weight gain and blood pressure (MANOVA model, P<0.0001).
Conclusions: GDM incidence in Greece presents seasonal variation. GDM risk diagnosis in summer is significantly increased (~70%) compared to winter. Diifferences in seasonal incidence are due to post glucose load levels. Whether the observed variations could be attributed to differences in ambient temperature or other environmental factors, remains to be clarified.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector
|Month||GDM %||RP||OR (95%CI)||Mean temp C|
|Jan||32.7||1||Rel to Jan||9.5|