Maternal outcomes following gestational diabetes
Around 700,000 women give birth in England and Wales each year; up to 5% of them have a diagnosis of diabetes in pregnancy [
1]. Among women with diabetes in pregnancy, gestational diabetes mellitus (GDM; described as abnormal glucose tolerance which first develops or is recognised during pregnancy) constitutes around 85% of cases, with the remainder due to pre-existing type 1 diabetes (T1D) or type 2 diabetes (T2D). The aetiology of GDM is not completely known but is due in part to the inability of the maternal pancreas to secrete sufficient insulin to cope with pregnancy-induced insulin resistance in susceptible women. The incidence of GDM is on the rise, in part due to higher rates of obesity in the general population, including in women of childbearing age [
2‐
4]. Estimates suggest that lifestyle factors such as obesity, smoking, unhealthy diet and physical inactivity may explain around 50% of the incidence of GDM [
5].
A diagnosis of GDM is associated with adverse outcomes for both the mother and her affected offspring. These women have higher risks of pre-eclampsia, Caesarean sections and an over sevenfold increase in the risk of developing T2D, with the highest incidence occurring within five years of the index pregnancy [
6‐
9]. Among parous women who have a diagnosis of T2D, ≤ 30% have a previous history of GDM, which means that pregnancy and the postnatal period within the first five years present a ‘golden opportunity’ to intervene and alter the natural course of a disease [
10,
11]. Additionally, women with a history of GDM have 2–3 times higher incidence of hypertension and ischaemic heart disease so any intervention provided in the postnatal period has the added potential of reducing cardiovascular disease risk [
8].
Fetal macrosomia (defined as birthweight > 4–4.5 kg) and large for gestational age (LGA) (defined as birthweight > 2 SD greater than mean or > 90th centile after controlling for age and sex) are two of the most common and serious offspring outcomes of GDM in pregnancy. Babies born to GDM mothers are 4–7 times likely to be macrosomic [
12,
13]. Other perinatal complications which are also associated with hyperglycaemia during pregnancy include shoulder dystocia and birth injuries, neonatal hypoglycaemia and respiratory distress syndrome [
14]. In the long term, offspring of women with GDM are at increased risk of obesity, hypertension, hyperlipidaemia and glucose intolerance starting from childhood and early adolescence thereby perpetuating the cycle [
15‐
17].
Role of lifestyle interventions to reduce T2D
There is evidence from observational studies that an active lifestyle (including increase in physical activity time and reduction in sedentary time) is associated with weight loss, improved glucose tolerance and lower risk of progression to T2D in women with a history of GDM [
18,
19]. The Diabetes Prevention Programme showed, with a randomised controlled trial (RCT) design, that intensive lifestyle interventions reduced the risk of incident T2D in adults with impaired glucose tolerance (IGT) by around 40–60% [
20,
21] and, in a subgroup of women with a history of GDM, by 53% and 35% over three and ten years, respectively, compared to standard care [
22,
23]. Other trials have shown decreases in rates of pre-diabetes, weight, waist circumference and lipid levels [
24‐
26]. Interestingly, treatment with metformin has been shown to confer no additional benefit to lifestyle interventions, presumably due to adherence issues and less weight loss in the first year of treatment when compared to the latter [
22].
However, there are several barriers to lifestyle interventions in postpartum women with recent GDM, including lack of time, balancing work and family demands, and lack of childcare [
27,
28]. Recently, a web-based lifestyle intervention program in 75 women in Boston, USA was deemed to be feasible and associated with significant weight reduction (3.3 kg below the control group) and higher likelihood of being below pre-pregnancy weight at 12 months postpartum [
29]. The program particularly recommended gradually increasing physical activity to 150 min per week, including resistance training and making healthier dietary choices.
While most of the abovementioned trials have suggested that a combination of exercise, healthy diet and weight loss or weight maintenance protects against diabetes in postpartum women, there is a lack of evidence about the independent effect of physical activity in reducing progression from GDM to T2D, particularly in high-risk populations such as minority ethnic groups. Indeed, in observational series, increase in moderate to vigorous physical activity, independent of body mass index (BMI), was associated with reduction in the risk of T2D in women after pregnancy [
18]. Among non-pregnant adults, every 2000 step per day change from baseline to 12 months is associated with an additional 8% decrease in the cardiovascular event rate [
30].
The ongoing and completed intervention programmes for women with a history of GDM have been conducted largely in women of white American, Australian or European background [
19,
23,
31,
32] and black, Hispanic and mixed minority American [
24,
33‐
35]. Therefore, there is a paucity of information about the feasibility and effectiveness of similar programmes for women in the UK, particularly in those of South Asian ethnicity. It is known that up to one in five South Asian adults globally have T2D and the diagnosis is 4–5 times more common in South Asian adults in the UK, compared to a white reference group [
36,
37].
Our study will therefore be novel in developing and testing an intervention that meets the cultural and social needs of women in a catchment area in that has a large multi-ethnic population (estimated to constitute 25–60% of the women diagnosed with GDM in the two research sites).