Early Versus Late Monitoring Among Pregnant Women With a History of Gestational Diabetes

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

The goal of this study investigate if pregnant women with a history of gestational diabetes (GDM) have better pregnancy outcomes if they test their blood glucose four times a day early in the pregnancy versus having an oral glucose tolerance test later in the pregnancy at 28 weeks in their current pregnancy.

Population being studied:

All pregnant women who had a history of GDM in a previous pregnancy

Study groups:

1. Women who are being managed in the pregnancy with early blood glucose monitoring (early monitoring group)
2. Women who are being managed with an oral glucose tolerance test at 28-32 weeks (late monitoring group)

This study has two parts (i) observational and (ii) mechanistic or laboratory based.

In the observational part of the study, data will be collected as standard of care across different obstetric units and this data will be used to:

1. compare the outcomes of the women such as need for labour to be induced, caesarean section rates, blood loss, need for treatment of their blood glucose with metformin or insulin, HbA1c values
2. compare the outcomes of the offspring such as birth weight centiles, shoulder dystocia or birth trauma, hypoglycaemia, jaundice and if admitted to the neonatal unit.

The mechanistic or laboratory part of the study is aimed at studying how the two different treatment approaches affect:

1. the metabolome of the pregnant woman - urine and blood samples collected at two time points will be used and mass spectrometry used to determine the amino acid and lipid profiles.
2. the microbiome differs between both groups
3. the pathways that regulate insulin in the placenta
4. the ability of the cells in the umbilical cord differentiate into the different fat cells.

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.

Inclusion Criteria:

1. Age >16
2. Pregnant
3. Previous pregnancy with gestational diabetes diagnosed by an Oral Glucose Tolerance Test
4. Singleton pregnancy

Exclusion Criteria:

Women with the following risk factors will be excluded:

1. Multiple pregnancy
2. History of bariatric surgery
3. Taking metformin or other oral hypoglycaemic agents
4. HbA1c more than or equal to 48