| Objective:Iron nutrition status is closely associated with maternal and infant health.The existing epidemiological evidence shows that elevated iron stores are associated with GDM risk.To investigate the effects of maternal iron status and iron supplementation during pregnancy on GDM risk,the aims of this study are as follows:1.To evaluate iron stores of pregnant women by assessing maternal plasma ferritin concentrations during pregnancy and examine the association between plasma ferritin concentrations,dynamic change of plasma ferritin concentrations and GDM risk.2.To investigate the use of iron supplements among pregnant women during pregnancy and examine the association between iron supplement use and GDM risk with baseline iron status considered.Methods:The participants in the present study are from the ongoing Tongji Maternal and Child Health Cohort(TMCHC),a population-based prospective cohort in Wuhan,China.Data on maternal demographics,socioeconomic status,medical and obstetrical history and lifestyle characteristics were collected using a structured questionnaire at enrollment.Prepregnancy weight was self-reported,and current weight and height were measured at enrollment.Information on dietary intake was obtained by a validated food frequency questionnaire(FFQ).Information on iron supplement use including brand,dose,starting time(gestational weeks),frequency(days/week),and week of discontinuation were collected by questionnaires at enrollment and the follow-up visits.Paticipants were categorized by iron supplementation during pregnancy into three groups: high iron supplementation(iron ≥60 mg/d,≥5 d/wk,≥4 wk),moderate iron supplementation(take iron supplements but not meeting the criteria of high iron supplementation),and nonusers(not take iron supplements).Peripheral venous blood samples were collected during gestational weeks 14-18 and 24-28 for mesurment of plasma ferritin concentrations.During gestational weeks 24-28,participants received a 75-g,2-h oral glucose tolerance test(OGTT)after an overnight fast.The log-Poisson regression model was used to estimate relative risks(RRs)and 95% confidence intervals(CIs)of GDM according to categories of plasma ferritin concentrations,iron supplement use and the combination of plasma ferritin concentrations in early and late pregnancy.Result:1.The present study involved 2117 participants with singleton live births.The mean age was 27.9 ± 3.1 years,and mean prepregnancy BMI was 20.8 ± 2.7 kg/m2.And 85.1% of the participants were nulliparous.A total of 219(10.3%)participants developed GDM.The medians and interquartile ranges of plasma ferritin concentrations during gestational weeks 14-18 and 24-28 were 52.1(29.6-89.9)ng/m L and 22.4(14.4-35.6)ng/m L,respectively.Of all the participants,1254(59.2%)were nonusers,448(21.2%)were classified as moderate iron supplementation,and 415(19.6%)were classified as high iron supplementation.2.Participants were categorized into 4 groups based on quartiles of plasma ferritin concentrations during 14-18 weeks’ gestation.The incidences of GDM across the increasing quartiles of plasma ferritin concentrations were 4.7%,10.8%,10.8%,and 15.1%,respectively.The adjusted RRs(95% CIs)of GDM across the increasing quartiles of plasma ferritin concentrations were 1.00(reference),2.14(1.37,3.34),2.03(1.30,3.19),and 2.72(1.76,4.21),respectively.Likewise,the adjusted RRs(95% CIs)of GDM across the increasing quartiles of plasma ferritin concentrations(24-28 wk)were 1.00(reference),0.71(0.42,1.20),1.42(0.91,2.21),and 1.78(1.17,2.72),respectively.3.Incidences of GDM for nonusers,moderate and high iron supplementation were 8.9%,10.9%,and 14.0%,respectively.Compared with nonusers,the adjusted RRs(95% CIs)of GDM for moderate and high iron supplementation were 1.11(0.81,1.53)and 1.37(1.02,1.84),respectively.When stratified by plasma ferritin concentrations during 14-18 weeks’ gestation,association between iron supplementation and GDM risk appeared to be more pronounced among participants with medium plasma ferritin concentrations(29.6-89.9 ng/m L).The adjusted RR(95% CI)was 1.64(1.08,2.49)for those with high iron supplementation,compared with nonusers.Among women with low(≤29.5 ng/m L)or high(≥90.0 ng/m L)plasma ferritin concentrations,no significant associations between iron supplementation and GDM were observed.4.Participants were categorized into four groups based on medians of plasma ferritin concentrations during gestational weeks 14-18 and 24-28.Participants with plasma ferritin concentrations below medians during gestational weeks 14-18 and 24-28 were reference.The adjusted RR(95% CI)of GDM for participants with plasma ferritin concentrations above median during 14-18 weeks’ gestation and below median during 24-28 weeks’ gestation was 1.85(1.09,3.11).Among participants with plasma ferritin concentrations above median during 24-28 weeks’ gestation,the adjusted RRs(95% CIs)of GDM for participants with plasma ferritin concentrations below,and above median during 14-18 weeks’ gestation were 2.41(1.51,3.86),and 2.34(1.55,3.53),respectively.Conclusions:Plasma ferritin concentrations were positively associated with risk of GDM.High iron supplementation(≥60 mg/d)was also related to an increased risk of GDM,and the association appeared to be more pronounced among women with medium plasma ferritin concentrations.The recommendations of iron supplementation during pregnancy should be made with individuals’ iron status considered,to reduce the risk of iron overload and GDM. |
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