Iron Supplement And Hemoglobin Concentration During Pregnancy Were Associated With An Increased Risk Of Gestational Diabetes Mellitus

Background and ObjectiveHemoglobin(Hb)measurement is a conventional test among pregnant women during perinatal visit.Hb concentration is related to iron supplement.Gestational diabetes mellitus(GDM),a common medical complication of pregnancy,is defined as “any degree of glucose intolerance with onset or first recognition during pregnancy”.It could bring serious hazards to maternal and offspring short and long term health.In recent years,the incidence of GDM has been increasing rapidly,and the related risk factors have drawn much attention.Most studies focused only on the association between maternal hemoglobin during pregnancy and risks for GDM,or association between iron supplement during pregnancy and risks for GDM,independently.Therefore,in was unclear that how iron supplementation and Hb are involved during the development of GDM.Besides,there was little known about different degrees of hemoglobin and iron supplement's effects on different time-point blood glucose levels during pregnancy(fasting blood glucose,postprandial blood glucose at 1 hour and 2 hour).This study aimed to determine whether Hb levels,iron supplement during pregnancy and its interaction effect were associated with different time-point blood glucose levels and the risk of gestational diabetes mellitus(GDM).MethodsThe prospective cohort study was conducted in Zhoushan maternal and Child Health Hospital,Zhejiang,from May,2011 to May,2018.The demographic data,lifestyles and information about iron supplement individually through questionnaires.Hemoglobin concentrations,blood glucose,gestational complication and disease history of each participant was extracted from electric medical information system(EMRS).Based on information from EMRS,multiple linear regression was applied for the association between Hb levels of first and second trimester of pregnancy(T1 and T2)and blood glucose.Multiple logistic regression was used for evaluating odds ratios between Hb levels and GDM.After information from EMRS and questionnaires combined,pregnant women were stratified according to whether they had anemia in T1 or T2,exploring the association between iron supplement in T1 or T2 and blood glucose.Information about hemoglobin and iron supplement was crossed for evaluation its interaction effect on glucose blood and GDM.ResultsA total population of pregnant women included into study were 1150.The incidence of GDM was 19.39%,and the incidence of anemia of T1 was 4.75%,of T2 was 25.48%.After controlled potential confounders,Hb levels of T1 were significantly and positively associated with fasting blood glucose(FBG),postprandial blood glucose at 1 hour(PBG1h)and 2 hour(PBG2h)(FBG: ?(se)=0.021(0.007),P=0.005,PBG1h: 0.121(0.027),<0.001,PBG2h:0.071(0.021),<0.001).Hb levels of T2 were significantly and positively associated with three time-point blood glucose(FBG: ?(se)=0.026(0.008),P=0.001;PBG1h: 0.065(0.029),<0.024;PBG2h: 0.049(0.022),0.026).Combined with the information of hemoglobin concentration and iron supplementation,the rate of iron supplement in T1 was 26.00%,that in T2 was 43.13%.The Hb concentrations in T1 and T2 were positively associated with OGTT1 h,and Hb levels in T2 was positively associated with risks for GDM.Iron supplement in T1 and T2 were not independently associated with blood glucose levels,and had no independent risks for GDM.But items of iron supplementation in T1 and Hb in T1,iron supplementation in T1 and Hb in T2,iron supplementation in T2 and Hb in T2,iron supplementation in T2 and Hb in T1 all had interaction effect on OGTT1 h blood glucose(P=0.005,0.015,0.049,0.017);and iron supplementation in T1 and Hb in T1,iron supplementation in T2 and Hb in T1 had interaction effect on the risk of GDM(P=0.001,0.028).Based on information hemoglobin and iron supplement,pregnant women without anemia in T2+iron supplement in T1 had significantly increased PBG1h(?(se)=0.313(0.150),P=0.037)and increased risks for GDM(OR=1.86,95%CI:1.06-3.25,P=0.029)compared with those with anemia in T2+without iron supplement in T1.Pregnant women without anemia in T2+iron supplement in T2 had significantly increased PBG1h(?(se)=1.009(0.166),P<0.001)and increased risks for GDM(OR=1.97,95%CI:1.17-3.42,P=0.013)compared with those with anemia in T2+without iron supplement in T2.Pregnant women without anemia in T1+iron supplement in T2 had significantly increased PBG1h(?(se)=0.627(0.021),P=0.021)and increased risks for GDM(OR=1.29,95%CI:1.05-3.55,P=0.005)compared with those with anemia in T1× without iron supplement in T2.Besides,based on information of iron supplement in T1 and T2,compared with pregnant women who didn't take iron supplementary both in T1 and T2,only iron supplement in T2 and iron supplement in T1 and T2 were positively associated with OGTT1h(only iron supplement in T2: ?(se)=0.441(0.022),P=0.022;iron supplement both in T1 and T2: ?(se)=0.539(0.247),P=0.030),and iron supplement both in T1 and T2 increased risks for GDM(OR=2.32,95%CI:1.37-3.96,P=0.002).ConclusionIncreased Hb concentration during pregnancy was significantly associated with FBG,PBG1 h,PBG2h and risks for GDM.The iron supplementation and hemoglobin during pregnancy had interaction effect on OGTT1 h blood glucose concentrations,and iron supplementation in T1 and Hb in T1,iron supplementation in T2 and Hb in T1 had interaction effect on the risk of GDM.Pregnant women without anemia in T1 taking iron supplementary in T2 or pregnant without anemia in T2 taking iron supplementary in T1 or T2 would increase PBG1 h levels and risks for GDM.It is not advised that pregnant women without anemia to use iron supplements during pregnancy.