The project aims to investigate gestational diabetes in women with a history of gastric bypass surgery (GBP). The investigators will analyse glucose levels by using continuous glucose measurement (GCM) or capillary glucose measurements and compare mean glucose values, treatment and the pregnancy outcome.

In Sweden the incidence of gestational diabetes is 2-5% of pregnancies, but the frequency varies greatly in different areas and in different ethnicities. The women with gestational diabetes have an increased risk of complications during pregnancy. The most acknowledged complications are large for gestational age infants (LGA), preeclampsia and caesarean section. The infants have a higher need for neonatal intensive care, due to the risk of hypoglycaemia, hypoxia and jaundice postpartum. Treating gestational diabetes and normalizing glucose values have been proven to reduce risks of unfavourable pregnancy outcome.

Gastric bypass surgery is a common treatment for obesity. The frequency of young women with gastric bypass surgery and concomitant gestational diabetes have increased. Many maternity care centres have started to use a 3-7 day screening for gestational diabetes, since the routine oral glucose toleration test (OGTT) is not recommended after GBP. It is previously shown that women with GBP have a decreased risk of GDM and LGA infants. However, there is an increased risk of small for gestational age (SGA). There is a lack of knowledge and guidelines regarding the optimal treatment of gestational diabetes in these women. How the glucose variability affects pregnancy outcome is poorly investigated. At Lund University Hospital, Region Skane, Sweden, the screening procedure used since 2012 for GDM-screening in women with GBP is a 3 day 7-point capillary glucose measurement. Approximately 25% of the pregnant women with GBP is diagnosed with GDM, using this method at Lund University Hospital.

In this project the investigators will randomize women with gestational diabetes and a history of gastric bypass (GDM-GBP) into two different groups in the last trimester of pregnancy. Both groups are given standard medical care, which includes visits to the Specialized Maternity Care Unit and weekly follow up by the diabetologist. The first group is given continuous glucose measurement (FreeStyle Libre3) and the other group is given standard medical care which includes 7-point capillary glucose measurement. With the CGM system it is possible to collect more comprehensive data regarding glucose values and variability. Previous studies have shown that women with gastric bypass surgery have an earlier than normal postprandial glucose excursion and are more prone to later postprandial hypoglycaemia. During this study, the physician as well as the patient can observe the early glucose excursion after meals and measure time in target, time above target and time below target. Large for gestational age and accelerated growth of the infant is supposed to be due to high glucose values and a high proportion of Time above target. The increased risk of SGA infants in these women is hypothesized to be due to a large proportion of time below target. However, this theory is not sufficiently investigated and it is not known if the use of CGM can help to reduce the risk of weight deviation in the infants.

The investigators want to examine if new technique in glucose measurement can contribute to more favourable pregnancy outcome in women with gestational diabetes and a history of GDM. The main question is if the use of CGM affect pregnancy outcome. The secondary outcomes includes glucose variability and the use of different treatment approaches in GDM in this group of women.