This study is designed to determine if a postnatal lifestyle intervention will lead to weight reduction over a 12 month period post-delivery in women who have been diagnosed with gestational diabetes mellitus and who have a BMI greater that 25 compared to women who receive routine care.

Diabetes during pregnancy (Gestational Diabetes Mellitus (GDM) is defined as high blood sugars during pregnancy and it is becoming increasingly common which affects around 18% of pregnant women. GDM is usually diagnosed by an oral glucose tolerance test around 28 weeks gestation. Women with previous GDM have a 50% risk of developing it again in any future pregnancy, and are 7 times more likely to develop type 2 diabetes within the future compared to women without GDM.

There is evidence that lifestyle changes (diet and physical activity), can reduce the development of type 2 diabetes in people at high risk, such as women with previous GDM. The postnatal period (shortly after pregnancy) is an ideal time for women to make these changes to help prevent weight gain between pregnancies and generally reduce their risk of future type 2 diabetes. This study is designed to determine if a postnatal lifestyle intervention will lead to weight reduction over a 12 month period post-delivery.

Women who have been diagnosed with diabetes during pregnancy (GDM) and had a body mass index (BMI) >25 kg/m2 at the start of pregnancy, will be invited to take part in the study.

During their routine appointment at 32-36 weeks gestation women will be randomly allocated either to the intervention program or control group.

Women in the intervention group, will receive a 1-hour educational session during their routine diabetes antenatal clinic visit. In addition, they will be offered an activity tracker (following consent) to help monitor their daily step count and physical activity.

Women in both the intervention and control groups will have a fasting glucose blood sample taken the morning after delivery. Those women with normal or borderline fasting glucose levels are eligible to remain in the study, but those with type 2 diabetes will be excluded and referred to their local diabetes team.

At 6-8 weeks postnatally, both groups will complete some questionnaires, give a blood sample, have weight and blood pressure measurements recorded. Women will be offered free referral to a commercial weight management organization for 12 weeks, with a possible extension for another 12 weeks). Over the 12 months of the study, the PAIGE2 team will contact participants intermittently by text and telephone to encourage them to eat healthily and increase their physical activity. If the participants' partner is also willing to take part, the partner will be sent an activity tracker to monitor physical activity and the research team will keep in intermittent contact with the partner by text and telephone during the study.

Women allocated to the control group will be offered a free 12-week referral to a commercial weight management organization at the end of the study.

Both groups will be asked to attend 2 further study visits at 6 and 12 months after delivery. This will involve completion of some questionnaires, a blood test, weight and blood pressure measurements.

Inclusion Criteria:

1. Women aged 18 years of age or older,

2. Women with a booking BMI ≥ 25 kg/m2 at <14 weeks gestation

3. GDM has been diagnosed in their current pregnancy.

4. Women will only continue to be included in the study if their fasting plasma glucose the morning after delivery indicates normality or impaired fasting plasma glucose outside of pregnancy (i.e.<7 mmol/l).

5. Women with a history of GDM directly preceding the current pregnancy, and who were given lifestyle advice and were performing self-monitoring of blood glucose from early pregnancy, will also be included if capillary glucose monitoring exceeds target values (fasting ≥ 5.3 mmol/l (95 mg/dl), 1h postprandial plasma glucose ≥ 7.8 mmol/l (140 mg/dl) thus negating the need for an OGTT.

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   Exclusion Criteria:

   Pregnancy in which an anomaly has been detected on the 20-week fetal anomaly scan.

b.) History of diabetes outside of pregnancy or FPG ≥7 mmol/l the morning after delivery.

c.) History of heart, liver or chronic renal disease. d.) Medications that adversely affect glucose tolerance (e.g. steroids). e.) Inability to participate in moderate physical activity outside of pregnancy.

f.) Moderate/severe depressive illness or excess alcohol consumption. g.) Inability to understand adequately verbal explanations or written information in English, or special communication needs.

h.) Women who are planning another pregnancy within the next 12 months following delivery.

i.) Exclusion criteria for early post-partum glucose testing will include massive postpartum hemorrhage, steroid treatment prior to delivery or patient refusal.

• If a woman requests an earlier discharge that does not allow time for the FPG test, she will be offered an appointment to return to the maternity unit within four weeks of birth for retesting.