Pregnancy can be more challenging for women with pre-existing (Type 1 or Type 2 diabetes) because it increases the risk of complications such as early births or babies being born larger than usual. Keeping blood sugar levels under control is very important to reduce these risks but the hormonal changes that happen during pregnancy make this harder to manage and can cause added stress for expectant mothers. There have been improvements in technology to monitor and manage blood sugar levels, however, there have not been many improvements in pregnancy outcomes in this population Physical activity and exercise during pregnancy have many benefits such as cardiovascular health and lower chance of pregnancy complications. For individuals with diabetes, physical activity can also help manage blood sugar levels and reduce insulin requirements. However, there is limited research on physical activity in women with pre-existing diabetes.

This study aims to find out how physical activity levels change throughout pregnancy, and how physical activity may be linked to blood sugar levels and diabetes related mental health. To determine what needs to be improved regarding physical activity during pregnancy in diabetes, it is crucial to first understand what activity patterns women engage in throughout pregnancy. In addition, what support is needed and when, will be explored Pregnant women (aged 18years or older) with a diagnosis of type 1 or type 2 diabetes before becoming pregnant will be invited to take part. Participants will be recruited during routine clinic visits.

Physical activity during pregnancy in women with pre-existing diabetes will be explored using both measurable activity data and patient experiences of being physically activity during pregnancy. Pregnant women with pre-existing diabetes will be invited to take part from early in their pregnancy. Participants will wear a wrist-based activity monitor for seven days in each trimester, complete an exercise diary and record meals through remote food photography during this time. At the end of each monitoring period, they will complete a questionnaire on diabetes-related emotional distress. Participants will share their continuous glucose monitor and insulin pump data (if applicable), with permission, through the online platforms they normally use to share data with their healthcare team.

Participants will have the option to join a focus group which will be held online via a video conferencing service (e.g.Zoom). This will involve group discussions will be audio recorded, and cover topics including experiences and feelings about physical activity, and what support regarding physical activity would they find useful.

There are no direct health benefits for participants, but the study may help improve future guidance and support for women with diabetes during pregnancy.

This study involves minimal risks. It requires no change in usual treatment or care, no additional clinical visits over and above those routinely scheduled, and no changes in usual behaviour. Within the observational study, there is a small risk of discomfort from wearing the activity monitor for seven days, if this becomes severe irritation, the participant will be informed they can remove the monitor and contact the research team. When conducting the focus groups there is a risk that some topics may bring out discussions which are sensitive, and the potential for participants being upset by something another participant may have said. If participants feel upset by participation in the focus group, they will be made aware they can leave at any time, and participants will directed to further support if required.

This is a multi-centre, mixed-methods observational study designed to examine physical activity patterns across pregnancy in women with pre-existing Type 1 diabetes (T1D) or Type 2 diabetes (T2D), and to investigate associations with glucose control and diabetes-related emotional wellbeing. The study integrates longitudinal quantitative assessments with qualitative insights into participant experiences.

The study will be conducted across NHS sites in the South West of England. Following informed consent, participants will be assigned a unique study identification number. The study is observational and does not involve any intervention or alteration to routine clinical care.

Quantitative Data Collection

Physical activity will be assessed using objective and self-reported measures. Device-measured physical activity will be collected using a GENEActiv wrist-worn accelerometer worn continuously for 7 days during each trimester (8-13, 18-22, and 26-31 weeks' gestation). Accelerometer data will be processed using validated analytical software to derive summary metrics including daily minutes of moderate-to-vigorous physical activity (MVPA), total activity, sedentary time, and sleep.

Structured exercise will be recorded using a study diary completed during each monitoring period. The diary captures activity type, timing, and perceived intensity, and includes prospective and retrospective components to characterise habitual behaviour.

Dietary intake will be assessed using the Remote Food Photography Method (RFPM). Participants will submit photographs of meals and snacks via secure digital platforms. Images will be linked to study data using the assigned study identification number.

Continuous glucose monitoring (CGM) data corresponding to each monitoring period will be obtained from routine clinical data-sharing platforms used in standard care. De-identified glucose data will be securely transferred for analysis. Glucose metrics will be derived according to international consensus standards, including time in range, mean glucose, and glycaemic variability.

Diabetes-related emotional wellbeing will be assessed at each monitoring period using the 20-item Problem Areas in Diabetes (PAID) questionnaire administered electronically.

Qualitative Component

A purposive sub-sample of ~16 participants will be invited to participate in online focus groups. Discussions will explore experiences of physical activity during pregnancy, perceived barriers and facilitators, interactions between activity and diabetes self-management, and perceived support needs. Sessions will be audio-recorded, transcribed verbatim, anonymised, and analysed using reflexive thematic analysis.

Data Management and Quality Assurance

All participants will be assigned a unique study identification number. Identifiable information will be stored separately from research data. Data transfers between sites and the coordinating centre will use secure, approved electronic systems. Data will be stored on secure institutional servers with restricted access.

Accelerometer and CGM data will undergo predefined processing and validation procedures to ensure completeness and plausibility. Range and consistency checks will be applied to quantitative variables prior to analysis. Qualitative transcripts will be reviewed against audio recordings to ensure transcription accuracy.

Sample Size Considerations

The target sample size is 175 participants (75 with T1D and 100 with T2D). The study is powered to detect a clinically meaningful change in daily MVPA across pregnancy, accounting for repeated measures and potential clustering by site.

Statistical Analysis

Changes in MVPA across pregnancy will be analysed using multilevel linear modelling to account for repeated measures within participants and clustering by site. Pregnancy stage will be modelled both categorically (trimester) and continuously (gestational week). Associations between physical activity, glucose metrics, and emotional wellbeing will be examined using regression-based approaches adjusted for relevant covariates.

Missing quantitative data will be examined to determine patterns of missingness. Multilevel models inherently accommodate unbalanced repeated measures; additional sensitivity analyses will be conducted if appropriate. Qualitative data will be analysed using Braun and Clarke's reflexive thematic analysis to identify themes related to behavioural capability, opportunity, motivation, and contextual influences.

The study does not include an interventional component and involves no modification to usual clinical management.

Inclusion Criteria:

• Women between 8 - 20 weeks pregnant (this will allow completion of at least two measures during pregnancy)
• Singleton pregnancy
• Confirmed diagnosis of T1D or T2D
• Over 18 years old
• Willing and able to provide informed consent
• Receiving care at one of the participating NHS sites

Exclusion Criteria:

• Multiple pregnancy
• Absolute contra-indication to PA according to 2019 Canadian Guidelines for physical activity during pregnancy , examples include ruptured membranes, preeclampsia and intrauterine growth restriction, full list available here37
• No diagnoses of T1D or T2D prior to pregnancy
• Gestational Diabetes

Eligible participants will be pregnant women with a diagnosis of T1D or T2D prior to conception.