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.