Prepregnancy diabetes, hyperglycaemic status, and adverse pregnancy outcomes in Chinese women: a population-based mega-cohort study

Abstract

BackgroundGestational diabetes is a well established risk factor for adverse pregnancy outcomes including preterm birth, low birthweight, and macrosomia. However, few studies have assessed the association of prepregnancy diabetes and fasting glucose levels with risk of adverse pregnancy outcomes. We aimed to examine the relations of prepregnancy diabetes and impaired fasting glucose with preterm birth, low birthweight, and macrosomia, using data from a mega cohort of women of reproductive age. MethodsThe China National Free Preconception Health Examination Project, established in 2010, included 1 464 523 couples from 220 counties who planned to conceive within 4–6 months of study entry to assess prepregnancy risk factors for birth defects. Participants had comprehensive physical examinations, responded to structured questions, and provided fasting blood samples for biomarker (including glucose) measurements before pregnancy and were followed up until 42 days after delivery. Diabetes was defined as self-reported diagnosed diabetes or fasting glucose concentrations of at least 7·0 mmol/L, and impaired fasting glucose as fasting glucose concentrations 6·1–7·0 mmol/L. Pregnancy outcomes were collected from 1 095 316 mothers between Jan 10, 2010 and Dec 31, 2015. Preterm birth was defined as live birth at 28–37 weeks gestational age, low birthweight as less than 2500 g regardless of gestational age, and macrosomia as birthweight of more than 4000 g. We used multivariate logistic regression models to estimate the odds ratios (ORs) and 95% CIs, with adjustment for covariates using normal live births as the denominators. This study was approved by the Institutional Research Review Board at the National Health and Family Planning Commission and National Research Institute for Family Planning. Written informed consent in Chinese was obtained from all participants or their legal representatives. Findings79 686 preterm births, 15 354 cases of low birthweight, and 33 667 cases of macrosomia were recorded. Compared with women whose blood glucose was less than 6·1 mmol/L before pregnancy, the risk of preterm birth was increased for those with impaired fasting glucose (OR 1·08, 95% CI 1·03–1·13) and those with diabetes (1·15, 1·08–1·22; ptrend<0·0001). The ORs of low birthweight were 1·16 (1·06–1·27) for women with impaired fasting glucose and 1·10 (0·97–1·26) for those with diabetes (ptrend=0·0023). The ORs of macrosomia were 1·00 (0·93–1·08) for those with impaired fasting glucose and 1·20 (1·09–1·31) for those with diabetes (ptrend<0·0001). InterpretationPrepregnancy diabetes and impaired fasting glucose are associated with an increased risk of adverse pregnancy outcomes. Therefore, early screening and preconception care for women with diabetes and impaired fasting glucose are important for optimisation of pregnancy outcomes. FundingFive-twelfth National Science and Technology Support Program.