An Observational Nested Multicenter Cohort Study of Early Versus Late Monitoring Among Pregnant Women With a History of Gestational Diabetes

Gestational diabetes rates are globally increasing and it is now well known that women who had gestational diabetes have a recurrent risk ranging from 35.5% to 70% in a future pregnancy. Some of these women may have preexisting type 2 diabetes or glucose intolerance There is also now convincing evidence that the women with GDM are at increased risk of T2DM and cardiovascular disorders. GDM can also affect the health of the offspring and associated with an increased risk of future obesity, diabetes and cardiovascular disorders, possibly modulated through altered epigenetics of the fetus. The recent NICE guidance has recommended that women with a history of GDM should be offered early pregnancy glucose monitoring or testing with oral glucose tolerance test at 24-28 weeks. Gestational diabetes is associated with derangement in amino acid and lipid pathways and these changes can be demonstrated several weeks prior to the diagnosis of GDM. Similarly, both candidate gene and genome wide studies have reported that GDM exposure is associated with significant changes in the infant's or child's DNA methylation, with a recent meta-analysis of seven pregnancy cohorts identified differentially methylated regions (DMRs) associated with GDM within OR2L13 and CYP2E1. Others have also been able to demonstrate that GDM-associated methylation is associated with offspring obesity and T2DM.

There is emerging evidence that in pregnancy gestational diabetes can occur as early as the first trimester. However in clinical practice, screening and diagnosis does not occur until 28 weeks in the pregnancy, suggesting that in some cases the fetus may be exposed to undetected hyperglycaemia much earlier. There is varying practice in how a pregnant women with a history of GDM is managed in a future pregnancy. Some are offered early capillary blood glucose testing four times a day as early as 10 weeks (early monitoring), while others are offered diagnostic testing with an oral glucose tolerance test at 28 weeks (late monitoring). This study was designed to compare the pregnancy outcomes between the early and the late monitoring approaches to determine which is more effective in modulating the maternal metabolome, placental insulin signalling pathways and offspring DNA methylation. Equally important the multi-centre observational arm will allow comparison of maternal and neonatal outcomes between both groups.