| Objectives: Generally,obesity is classified into general obesity and central obesity and is related to the risk of gestational diabetes mellitus(GDM).This study foucused on 1)checking how high is high enough for body mass index(BMI)and waist circumference at early pregnancy to increase the risk of GDM and whether there is an interaction both risk factors for GDM;2)developing a simple obesity score for prediction of GDM;3)documenting the prevalence and determinants of general obesity and central obesity at early pregnancy in pregnant women in Tianjin.Methods From July 1,2010 to September 30,2012,19,669 pregnant women were registered within the first 12 gestational weeks(range: 4–12 weeks)at primary care hospitals in Tianjin,China.A questionnaire of “Health questionnaire during early pregnancy” was filled out,including women's basic information and anthropometry data.A two-step GDM screening procedure was used to identify GDM cases.All pregnant women were routinely offered a non-fasting 50-g 1-h glucose challenge test between 24 th and 28 th weeks of gestation at primary care hospitals.Women with positive glucose challenge test,i.e.,?7.8 mmol/L,were referred to a centralized GDM clinic located within Tianjin Women and Children's Health Center,where they underwent a standard 75-g 2-h oral glucose tolerance test(OGTT).All women filled out a “Health questionnaire during mid trimester pregnancy” of collecting the realted information and anthropometry data.We sequentially excluded 1,080 women without performing the glucose challenge test,781 who had a positive glucose challenge test but did not undergo the OGTT and 5 with pre-existing diabetes.The remaining 17,803 pregnant women were included in the third parts analysis.Binary logistic regression was used to obtain odds ratios(ORs)and 95% confidence intervals(CIs)of influence factors of general obesity and central obesity.Restricted cubic spline was used in binary logistic regression model to plot the OR curves of WC and BMI for GDM.Additive interactions between high BMI and high WC were estimated and a GDM risk score was established.Receiver's Operating Characteristic Curve(ROC)curve was used to obtain the cutoff point of GDM risk score.A total of 19,662 women with complete BMI information were included in the analysis of the general obesity and 18,043 women with complete WC information were included in the central obesity analysis.Results : 1383 pregnant women developed gestational diabete mellitus and the prevalence of GDM were 7.8%.The mean age of the Tianjin pregnant women were 28.5(SD:2.8).The mean BMI of Tianjin pregnant women were 22.3(SD:3.4)kg/m~2 and the mean WC of were 78.8(SD:8.7)cm.1)Interactive effect of BMI and WC on GDM: The risk of GDM increased steeply from BMI up to 22.5 kg/m~2 onwards.If BMI <22.5 kg/m~2 was used as the referent,overweight and subclinical overweight were associated with increased risks of GDM in both univariable and multivariable analyses(multivariable OR: 2.84,95%CI: 2.47-3.26 for overweight;1.76,95%CI: 1.47-2.10 for subclinical overweight).The risk of GDM increased steeply from WC up to 78.5 cm onwards in a linear manner.If WC <78.5 cmwas used as the referent,central obesity,i.e.,WC ?85.0 cm and subclinical central obesity,i.e.,WC ?78.5 but <85.0 cm,were associated with increased risks of GDM in both univariable and multivariable analyses(multivariable OR: 2.58,95%CI: 2.23-2.98 for central obesity;1.53,95%CI: 1.31-1.78 for subclinical central obesity).After further adjustment for BMI,the ORs remained significant(central obesity: 1.60,95%CI: 1.34-1.91;and subclinical central obesity: 1.18,95%CI: 1.00-1.40).There was an additive interaction between WC ?78.5 cm and BMI ?22.5 kg/m~2 in conferring increased risk of GDM in both univariable and multivariable analyses.Co-presence of BMI ?22.5 kg/m~2 and WC ?78.5 cm significantly enhanced the effect sizes of presence of either BMI ?22.5 kg/m~2 alone or WC ?78.5 cm alone for risk of GDM.2)Obesity score for GDM: The area under ROC was 0.648(95% CI: 0.632-0.665)with the cutoff point of 1.50 giving a sensitivity and specificity of 61.8% and 62.2%,respectively3)The mean BMI of Tianjin pregnant women were 22.3(SD:3.4)kg/m~2 and the prevalence of subclinical general overweight was 13.7% while the prevalence of general overweight was 24.9%.The mean WC of Tianjin pregnant women were 78.9(SD:8.7)cm and the prevalence of subclinical central obesity was 25.1% while the prevalence of central obesity was 23.3%.The determinants of high BMI: Age(OR/5 years:1.21,95%CI:1.14-1.29),family history of diabetes(OR:1.61,95%CI:1.44-1.80),multiple pregnancies(OR:1.08,95%CI:1.01-1.17),education(OR: 0.64,95%CI:0.59-0.71),monthly income 3000<~?5000(OR: 0.83,95%CI:0.71-0.97)and >5000 RMB(OR: 0.95,95%CI:0.74-0.99)were associated with increased risk of high BMI in multivariable analysis.The influence factors of large WC: Age(OR per 5 years:1.22,95%CI:1.15-1.30),family history of diabetes(OR:1.38,95%CI:1.23-1.55),multiple pregnancies(OR:1.13,95%CI:1.05-1.22),education(OR:0.79,95%CI:0.72-0.87)and smoke before pregnancy(OR:1.31,95%CI:1.09-1.59)were associated with increased risk of large WC in multivariable analysis.Conclusion: BMI at ?22.5 to <24.0 kg/m~2 and WC at ?78.5 to <85.0 cm measured within 12 weeks of pregnancy were independently associated with increased risks of GDM among Chinese pregnant women.Co-presence of body mass index ?22.5 kg/m~2 and waist circumference ?78.5 cm interacts to further increase the risk of GDM.High BMI defined as BMI ?22.5 kg/m~2 and large WC defined as WC?78.5 cm were highly prevalent.The determinants of high BMI included age,education,multiple pregnancies,family history of diabetes and monthly income.Similarly,the determnants of large WC involved age,education,multiple pregnancies,family history of diabetes,monthly income and smoke before pregnancy. |
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