Description of the condition

Gestational diabetes mellitus (GDM) is defined as 'carbohydrate intolerance resulting in hyperglycaemia of variable severity with onset or first recognition during pregnancy' (WHO 1999). This definition includes women who first present with type 1 or type 2 diabetes during pregnancy, or where diabetes was previously undetected. Although GDM typically resolves following birth, it is associated with adverse outcomes for both mother and infant, both in the perinatal period and in the long term.

In subsequent pregnancies of women with a history of GDM, one of the main issues is recurrence of GDM and the associated outcomes. Irrespective of subsequent pregnancies, other long‐term considerations for these women include the development of type 2 diabetes, metabolic syndrome and the risk of cardiovascular disease.

Description of the intervention

Interconception care may encompass a variety of interventions, including education, dietary and lifestyle advice, pharmacological intervention and active surveillance for illness and complications. It includes care between the birth of one child to the next pregnancy.

Internationally, clinical practice guidelines and consensus statements generally recommend postpartum assessment for continuing glucose intolerance after six to 12 weeks, by oral glucose tolerance testing to detect type 2 diabetes, and on a regular basis thereafter (i.e. every one to three years thereafter depending on other risk factors) (ACOG 2013; ADA 2017; CDA 2013; Metzger 2007; Nankervis 2014; NICE 2015). Despite such recommendations, a high proportion of women with previous GDM do not have testing for diabetes in the postpartum period (Blatt 2011). A Cochrane review evaluating 'Reminder systems for women with previous GDM to increase uptake of testing for type 2 diabetes or impaired glucose tolerance', showed low‐quality evidence supporting an increase in the uptake of testing for type 2 diabetes in women with previous GDM following the issue of postal reminders (Middleton 2014).

While often recommended, there is little evidence on what care women with a history of GDM should receive prior to a subsequent pregnancy. Clinical guidelines recommend that women be assessed preconceptually for a medical review and/or an oral glucose tolerance test, with early evaluation for glucose intolerance during pregnancy (ACOG 2013; NICE 2015). In addition to earlier identification and management of diabetes, interconception care after the postpartum period would ideally aim to target the modifiable risk factors for GDM, thus improving women's metabolic profiles.

How the intervention might work

In a survey of women with a history of GDM within the last five years, while 90% understood that previous GDM placed women at high risk of type 2 diabetes, only 16% believed that they themselves were at high risk of developing diabetes (Kim 2007b). This was partially explained by women planning to improve their behaviour in the future. When women considered the risks if they continued their current lifestyle, this risk perception rose to 39%. Importantly 85% of these women had plans for risk‐reducing behaviour (Kim 2007b). Another survey comparing women with children and a history of GDM with women with children without a history of GDM, found that those with a history of GDM were more likely to smoke and less likely to meet fruit and vegetable consumption recommendations (Kieffer 2006).

The interconception period provides an opportunity to provide advice on potential risks and possible interventions to improve health. Moreover, it provides the opportunity to identify undiagnosed pre‐existing diabetes. Since women with a history of GDM are at increased risk of diabetes, and pre‐existing diabetes in pregnancy is linked to poor maternal and infant health outcomes, it is important to identify and manage accordingly in the interconception period.

Risk factor reduction is a potential area of focus for these women, targeting modifiable risk factors such as maternal obesity where dietary and lifestyle interventions could be implemented and potentially benefit women with a history of GDM. Reducing maternal obesity itself may also lead to better maternal and infant health outcomes outside of its potential effect in the prevention of GDM. Regardless of whether women subsequently become pregnant, such interventions may improve the health of these women.

There is little information on the value of pharmacological agents such as oral anti‐diabetics for women with a history of GDM in the preconceptual period; assessed in the Cochrane review, 'Oral anti‐diabetic agents for women with pre‐existing diabetes mellitus/impaired glucose tolerance or previous gestational diabetes mellitus' (Tieu 2010b). The use of oral anti‐diabetic agents has been predominantly in the setting of polycystic ovarian syndrome or for prevention of type 2 diabetes in women with a history of GDM. 'Interventions for the prevention of type 2 diabetes in women with previous gestational diabetes' will be the focus of a planned Cochrane review (Li 2017).

Why it is important to do this review

Women with a history of GDM are recognised to be at high risk for recurrence in subsequent pregnancies, type 2 diabetes and cardiovascular disease, and therefore, for adverse maternal and infant health outcomes. While management of GDM is worthwhile, interconception care for these women also has the potential to improve maternal and infant health. Interconception care may also allow for detection and appropriate management of asymptomatic pre‐existing diabetes and provide an opportunity for risk factor reduction and, potentially, prevention of recurrent GDM and its sequelae.

Routine pre‐pregnancy care and preconception care for women with known diabetes mellitus are reviewed by the Cochrane reviews 'Routine pre‐pregnancy health promotion for improving pregnancy outcomes' (Whitworth 2009) and 'Preconception care for diabetic women for improving maternal and infant health' (Tieu 2010).