Introduction

In Scotland, around 1 in 175 pregnancies is complicated by pre-existing diabetes, of which around 70% are type 1 diabetes mellitus (T1DM) and 30% are type 2 diabetes mellitus (T2DM). National surveillance of pregnancy, childbirth and early care of babies in Scotland shows that maternal obesity continues to increase. In 2021–2022 the proportion of women giving birth who were overweight or obese was the highest since reporting began (56.9%).¹ In 2022, 67% of adults with T1DM and 89% of adults with T2DM were overweight or obese.² Depending on screening pathways, up to 11% of pregnancies may be complicated by incident gestational diabetes (GDM) and early screening may detect up to 3% of women with likely undiagnosed diabetes in early pregnancy.³

For women with pre-existing diabetes adverse outcomes, including increases in miscarriage, congenital anomaly, pre-eclampsia, operative deliveries, neonatal hypoglycaemia and neonatal intensive care unit admission (NICU) and stillbirth, have been slow to improve. Major technological advances in both glucose monitoring, including development and implementation of various forms of continuous glucose monitoring, and insulin delivery, including pump and integrated pump and sensor technology, have become available in the last five years. Consideration of the place of such technologies in supporting improvements in self management for these women is now particularly important.

For women with, or at risk of GDM, there are related and additional challenges. Firstly, all services report increases in women at risk of GDM, based on increasing prevalence of risk factors including, but not confined to, adiposity and ethnicity. Further, new evidence and new recommendations have been published on criteria for detection and diagnosis of GDM since the publication of the previous version of this Scottish Intercollegiate Guidelines Network (SIGN) guideline in 2010.⁴ Revisiting the optimal approach to screening and diagnosis of GDM in Scotland balances the priorities to avoid missing a diagnosis and the opportunity to improve outcomes, but also to avoid medicalising pregnancy if this can be avoided.

The guideline development group notes that, as with T2DM, GDM is more prevalent in people from economically disadvantaged groups⁵ and ensuring that testing and treatment are made available to all women on an equitable basis is a key aim of service delivery.

The guideline development group has sought to apply the best evidence to encourage the most appropriate level of care for women with diabetes in Scotland.

Patients may have different perspectives on healthcare processes and outcomes from those     of healthcare professionals. The involvement of patients in guideline development is therefore important to ensure that guidelines reflect their needs and concerns and address issues that matter to them. The guideline development group included two members with diabetes who have experienced pregnancies. The group also included representation from Diabetes Scotland who engage with, represent and advocate for people living with diabetes.

SIGN contacted organisations which represent women with diabetes, including Diabetes Scotland, The Alliance, the Insulin Pump Awareness Group (IPAG) Scotland, the British Heart Foundation (BHF), Chest Heart & Stroke Scotland (CHSS) and Carers Trust Scotland, to identify issues of concern. We also asked members of the SIGN Patient and Public Involvement Network to highlight any relevant issues.

Common concerns raised by patient groups and through research include:

·     Access to diabetes technologies (for example continuous glucose monitoring) to support managing diabetes as best as possible during pregnancy.

·     Being informed and listened to during discussions and decision making around pregnancy and birth. Making sure that conversations start with what matters most to the woman.

·     Having timely access to support throughout pregnancy to help manage concerns particularly around sickness, increased hypos, or sudden increases in insulin requirements.

During consultation on this guideline, reviewers raised the issue of women feeling that their body weight or body mass index (BMI) is the main focus of clinical discussions, and that they often feel labelled, blamed and guilty that, due to their diet and lifestyle, they have placed their pregnancy and baby at risk. The guideline development group acknowledges the importance of communicating risks associated with pregnancy in a way which is individualised to the woman, is sensitive and avoids implying blame and which encourages clear and accurate information provision using person-centred language.

This guideline provides recommendations based on current evidence for best practice in the management of diabetes in pregnancy. It includes major milestones in the pregnancy journey from preconception care to follow up and surveillance in the weeks after delivery. The target population includes:

·     women with T1DM or T2DM who are planning pregnancy

·     women who have previously had GDM

·     pregnant women who do not have a pre-existing diagnosis of diabetes

·     pregnant women with GDM

·     women with moderately-raised glycated haemoglobin (HbA1c) (42–47 mmol/mol)

·     women with specific risk factors for adverse pregnancy outcomes, including current or previous intrauterine death (IUD), polycystic ovary syndrome (PCOS), age >35 years and/or Chinese or East Asian ethnicity.

Intrapartum care is not included in the remit of this guideline. The Joint British Diabetes Societies for Inpatient Care guideline Managing diabetes and hyperglycaemia during labour and birth contains advice and recommendations developed using informal consensus to support management of glucose control when pregnant women with diabetes are admitted to obstetric wards.⁶ Other than in the specific context of management of women with GDM, prevention or remission of type 2 diabetes is not included in the remit of this guideline. These, and further issues are covered by SIGN 172: Prevention, early recognition and treatment, and remission of type 2 diabetes.

Common comorbidities and coexisting health issues which have been considered when reviewing the evidence for this guideline are:

·     Obesity

·     cardiovascular disease, in particular hypertension and dyslipidaemia

·     diabetic kidney disease

·     diabetic eye disease

·     diabetic foot disease.

·     Consideration of these factors is particularly important in pregnancy planning.

The term woman/women is used throughout this document to refer to women and birthing people who are pregnant or who recently gave birth. It refers to people who share the protected characteristic of pregnancy and maternity when naming the beneficiaries of work which affects prenatal, perinatal and postnatal care. The Women’s Health Plan published by Scottish Government in 2021 notes that while the majority of those who are pregnant and having a baby will identify as women, all healthcare services should be respectful and responsive to individual needs, and all individuals should be asked how they wish to be addressed throughout their care.⁷ For the purpose of this document, the term woman/women includes girls. It also includes people whose gender identity does not correspond with their birth sex or who may have a non-binary identity.

Continuous glucose monitoring (CGM) provides people with diabetes with real-time information on glucose levels. A sensor is worn on the skin and measures glucose levels in the interstitial fluid. Information on glucose concentration is recorded every few minutes and is transmitted to a reader, smartphone or other device, such as a smart watch. This continuous glucose data can provide information on glucose trends throughout the day and overnight. Changes in interstitial glucose and therefore sensor glucose will lag 5–10 minutes behind changes in blood glucose.

There are two main types of CGM. Intermittently-scanned CGM (isCGM, or flash CGM) requires the user wearer to actively scan the sensor (which can be worn for up to 14 days without the need for user calibration) in order to display glucose information. Real-time CGM (rtCGM) automatically measures glucose levels and displays the most recent value. Real-time CGM systems have the ability to predict high and low glucose levels, and alarms can be set to alert the wearer. While  the distinction between isCGM and rtCGM has been present during the development of this technology and is retained within this guideline in the descriptions of the historical evidence base, at time of publication, most CGM devices used in Scotland transmit glucose data in real time and recommendations will use the term CGM to reflect the current routine clinical use of rtCGM.

Hyperglycaemia in pregnancy/gestational diabetes

The World Health Organisation (WHO), in 2013, defined hyperglycaemia first detected at any time during pregnancy as either diabetes mellitus in pregnancy or gestational diabetes mellitus with definitions based on results of a 75 g oral glucose tolerance test (OGTT).⁸ The subdivision may be clinically useful as higher degrees of glycaemia at diagnosis may be associated with worse outcomes. It excludes women known to have diabetes before pregnancy. While recognising the likely utility of that division, in this document the term gestational diabetes will also refer to women found to have hyperglycaemia as result of testing in pregnancy, as reflected by much of the literature.

The WHO report did not consider role of HbA1c, particularly in early pregnancy. We recognise that some women will have HbA1c in the diagnostic range of diabetes in early pregnancy and suggest that those women are diagnosed as having likely pre-existing diabetes. There may be some women, particularly where prediabetes is present before pregnancy or in early pregnancy, who will have home monitoring above target values but have not had a formal OGTT. In these circumstances women are treated in the pathway for gestational diabetes.

Hyperglycemia and Adverse Pregnancy Outcomes study – odds ratios 1.75 and 2.0

The objective of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study was to clarify associations of levels of maternal glucose lower than those diagnostic of diabetes with perinatal outcome. This was accomplished by performing a 75 g OGTT on a heterogeneous, multinational, multicultural, ethnically diverse cohort of approximately 25,000 women in the third trimester of gestation. This provided data on associations between maternal glycaemia and risk of specific adverse outcomes that could be used to derive internationally acceptable criteria for diagnosis and classification of GDM. Results of this study show strong linear associations of risks for >90th percentiles of birth weight, cord C-peptide, and percentage body fat with each of three measures of maternal glucose (fasting plasma glucose (FPG), one-hour, and two-hour post–75 g load).⁹ Subsequently, the International Association of Diabetes and Pregnancy Study Groups (IADPSG) used associations with these outcomes to select glucose concentrations as potential diagnostic threshold values. The IADPSG consensus panel concluded that the predefined value for the odds ratio at the diagnostic threshold relative to the mean should be 1.75. That is, the diagnostic thresholds are the average glucose values at which odds for birth weight >90th percentile, cord C-peptide >90th percentile, and percent body fat >90th percentile reached 1.75 times the estimated odds of these outcomes at mean glucose values of the HAPO cohort, based on fully adjusted logistic regression models. These thresholds (FPG ≥5.1 mmol/L, or one-hour postload plasma glucose ≥10.0 mmol/L or two-hour postload plasma glucose ≥8.5 mmol/L) represent the IADPSG diagnostic criteria for GDM (and are equivalent to HAPO 1.75 odds ratios). The IADPSG consensus panel also considered, but did not set, alternative diagnostic criteria at glucose levels where the odds for these clinical outcomes reached 2.0 times the estimated odds of these outcomes at mean glucose values of the HAPO cohort (ie HAPO 2.0).¹⁰ Alternative screening and diagnostic strategies for GDM are discussed and compared in section 5.2, including the diagnostic thresholds represented by HAPO 1.75 (or IADPSG) and HAPO 2.0.

This guideline will be of interest to healthcare professionals in primary and secondary care involved in the care of women with diabetes and their newborn babies, including general practitioners (GPs), nurses and midwives, obstetricians, diabetes physicians, neonatal paediatricians, dietitians and pharmacists. It will also be of interest to women with pre-existing diabetes, those who develop diabetes during pregnancy and their families.

A plain language version of this guideline is available from the SIGN website www.sign.ac.uk.

This guideline is not intended to be construed or to serve as a standard of care. Standards of care are determined on the basis of all clinical data available for an individual case and are subject to change as scientific knowledge and technology advance and patterns of care evolve. Adherence to guideline recommendations will not ensure a successful outcome in every case, nor should they be construed as including all proper methods of care or excluding other acceptable methods of care aimed at the same results.

The ultimate judgement must be made by the appropriate healthcare professional(s) responsible for clinical decisions regarding a particular clinical procedure or treatment plan. This judgement should only be arrived at through a process of shared decision making with the patient, covering the diagnostic and treatment choices available. It is advised, however, that significant departures from the national guideline or any local guidelines derived from it should be documented in the patient’s medical records at the time the relevant decision is taken.

It has been recognised that financial or academic interests may have an influence on the interpretation of evidence from clinical studies.

It is not possible to completely eliminate any possible bias from these sources, nor even to quantify the degree of bias with any certainty. SIGN requires that all those involved in the work of guideline development should declare all financial and academic interests, whether direct or indirect, annually for as long as they are actively working with the organisation. By being explicit about the influences to which contributors are subjected, SIGN acknowledges the risk of bias and makes it possible for guideline users or reviewers to assess for themselves how likely it is that the conclusions and guideline recommendations are based on a biased interpretation of the evidence.

Signed copies of declaration of interests forms are retained by the SIGN Executive and a register of interests is available in the supporting material section for this guideline at www.sign.ac.uk

Recommendations within this guideline are based on the best clinical evidence. Some recommendations may be for medicines prescribed outwith the marketing authorisation (MA) also known as product licence. This is known as ‘off-label’ use.

Medicines may be prescribed ‘off label’ in the following circumstances:

·     for an indication not specified within the marketing authorisation

·     for administration via a different route

·     for administration of a different dose

·     for a different patient population.

An unlicensed medicine is a medicine which does not have MA for medicinal use in humans.

Generally ‘off-label’ prescribing of medicines becomes necessary if the clinical need cannot be met by licensed medicines within the marketing authorisation. Such use should be supported by appropriate evidence and experience.¹¹

“Prescribing medicines outside the conditions of their marketing authorisation alters (and probably increases) the prescribers’ professional responsibility and potential liability”.¹¹

The General Medical Council (GMC) recommends that when prescribing a medicine ‘off label’, doctors should:¹²

·     be satisfied that there is no suitably licensed medicine that will meet the patient’s need

·     be satisfied that there is sufficient evidence or experience of using the medicine to show its safety and efficacy

·     take responsibility for prescribing the medicine and for overseeing the patient’s care, including monitoring the effects of the medicine, and any follow-up treatment, or ensure that arrangements are made for another suitable doctor to do so.

·     make a clear, accurate and legible record of all medicines prescribed and, when not following common practice, the reasons for prescribing an unlicensed medicine.

Non-medical prescribers should ensure that they are familiar with the legislative framework and Royal Pharmaceutical Society’s Competency Framework for all Prescribers.

Prior to any prescribing, the licensing status of a medication should be checked in the summary of product characteristics (www.medicines.org.uk). The prescriber must be competent, operate within the professional code of ethics of their statutory bodies and the prescribing practices of their employers.¹³

Specialist teams within Healthcare Improvement Scotland issue a range of advice that focuses on the safe and effective use of medicines and technologies in NHSScotland.

The Scottish Medicines Consortium (SMC) provides advice to NHS boards and their Area Drug and Therapeutics Committees about the status of all newly-licensed medicines, all new formulations of existing medicines and new indications for established products. NHSScotland should take account of this advice and ensure that medicines accepted for use are made available to meet clinical need where appropriate.