Maternal Iron Status During the First Half of Gestation With Subsequent Risk of Gestational Diabetes and Adverse Birth Outcomes

OBJECTIVES: The study aims to investigate the association of maternal iron status with subsequent risk of gestational diabetes mellitus (GDM) and adverse birth outcomes. METHODS: This was a longitudinal study embedded in Huizhou Birth Cohort. Eligible singleton pregnant women of 15 to 49 years were enrolled during their first antenatal visits from December 2018 to October 2019. Maternal serum ferritin (SF) and haemoglobin (Hb) and lipids were tested before 20 weeks of gestation. GDM was diagnosed by a standardized 75g oral glucose tolerance test (OGTT) at 24 to 28 gestational weeks. Birth outcomes were retrieved from the Hospital Information System. The adverse birth outcomes of small for gestation age (SGA) and large for gestation age (LGA) were diagnosed in accordance with an established criteria of Chinese population according to birth weight and gestational week at delivery. Multivariable linear and logistic regression models were applied to examine the associations of maternal iron status with the risk of GDM and adverse birth outcomes. The interactions of iron markers and lipids were explored to testify their combined impacts on GDM and birth outcomes. RESULTS: Total 2906 eligible mothers and their neonates were included for data analysis. The prevalence of GDM, SGA and LGA were 18.6%, 11.5% and 4.0%, respectively. Multivariable linear regression indicated that SF was positively associated with post-load glucose levels, while inversely linked with birth weight and height (all P < 0.05). Compared with the lowest quartile group, the highest quartile of Hb were significantly associated with increased risk of GDM by 48.4% (OR = 1.484, 95% CI:1.094–2.013, P(trend )< 0.05); the highest quartile of SF was significantly associated with increased risk of SGA by 47.0% (OR = 1.470, 95%CI:1.012∼2.137, P(trend )= 0.022) and decrease risk of LGA by 52% (OR = 0.480, 95% CI:0.245∼0.940, P(trend )= 0.017). A significant multiplicative interaction was observed between Hb and total cholesterol (TC). High levels of Hb and TC increased the risk of SGA by 73.2% (OR = 1.732, 95% CI:1.035–2.898, P = 0.037). CONCLUSIONS: Maternal SF and Hb were positively associated with increased risk of GDM and post-load glucose level. Higher SF was associated with increased risk of SGA while decreased risk of LGA. FUNDING SOURCES: One Hundred Person Project of Sun Yat-sen University (Funding no. 51,000–18,841,203).