Table 4.

Additional Participant Quotations

Themes/subthemes	Participant quotations
Managing T1D pregnancy before closed-loop
Physical, mental, and emotional demands	Needing to set alarms at night: “The hardest thing is at night I think, ‘cause I've quite a fear of going low. So I'd set about three alarms overnight (laughs). You just end up not sleeping very well at all and I think that can kind of get you down.” (010) “With my other pregnancy they wanted overnight readings. They wanted them at a certain time, so I'd have to set my alarm, wake myself up, test my blood, go back to sleep… it was exhausting.” (014)
Negative pregnancy experiences	Becoming obsessed about monitoring and over-correcting: “I've been using a lot of temporary basals, and if anything I was doing overcorrection sometimes. So I was finding I was, you know, I'd be hypo and then sort it out, and then I'd get a massive rebound high… So I was getting a lot of peaks and troughs, and I was finding that very stressful.” (022)
Experiences of closed-loop
Adjusting to the system	Frequent data checking to seek reassurance: “It felt as though I was just constantly watching, making sure that it was doing its job, so I would be probably looking at it anywhere between- I would probably say six to ten times a day. I was constantly checking on it.” (019) Contacting HCPs for information and support: “It was easier to explain when you are using it, rather than as you set it up, you know, it's easy to say: oh this one means it's rising, this one means it's lowering, but it's not until I started using that that I realised I didn't actually fully understand the function and needed a bit more support.” (014) “The training was very good, it was thorough, but you will be learning as you start to use it… I've messaged [names staff member] a couple of times, initially particularly when my sugars were going high, I was like: normally I'd give a correction here, I'm going to put the Boost function on: is that right?… Shall I use it for this amount of time or longer? - So it's just that clarification.” (022)
Less work, less worry… better glucose control	Remote insulin administration facilitating more time in range: “Before… if my Libre said I was 12 [mmol/L - 216 mg/dL] and I was in the playground with lots of other mums … and I knew I was going home in half an hour, then I wouldn't get my insulin pen out to give myself a correction… especially when you're pregnant, you don't wanna get your tummy out to (laughing) give yourself an injection… whereas you can do that now. So again, that's another factor that just means your time in target must be, yeah, just hugely better.” (011) Experiencing better sleep: “I think obviously being the closed-loop, it adjusts for you…in the background… ‘cause I never really knew what my overnights were. Even with the Libre you have the Libre lows, my overnights were sort of all over the place. Whereas now I could have a steady night, and obviously sleep, and not have to worry too much about it.” (021) “It's definitely took the worry away for me, ‘cause I'm quite active in the day with my kids anyway, so if I'm dipping low and I'm busy with the kids, I'm then alerted before anything goes wrong, because if I was to, God forbid, have a hypo and not be responsive with my children, it would be awful.” (011)
But still work… user collaboration with closed-loop	Needing to create the conditions to help the technology work optimally: “I still think… a lot of it is your own doing and the information you're putting in and when. Em, so your carb counting, the time before you're gonna eat…” (017) Seeing both insulin and glucose data helps make better management decisions: “Having the visualisation of the graph, knowing that it's not delivering any insulin at the minute… I think that's really helpful to know that it's already eased off, so I probably haven't got that much insulin in me that's going to send me lower. So you know, that one jelly baby is going to bring me back up to the level.” (007) Needing to know when and how to intervene: “The main thing I've struggled with is, like, obviously before when my levels went high I would just put a correction dose in… But I've still kind of struggled to know… when I should put a correction in or whether I should just let the phone do its own thing.” (010) “I've messaged (names trial staff) a couple of times, when I was sort of- initially particularly when my sugars were going high, I was like: normally I'd give a correction here… I'm gonna put the boost function on: is that right?” (022)
Collaboration with closed-loop features: using Ease-off and Boost	Using Boost when the closed-loop is perceived as being too sluggish: “Sometimes I use [Boost] where I think the algorithm hasn't been as generous as I think it needs it to be, because that's just the algorithm still learning, because I'm extremely insulin resistant.” (022) Applying own knowledge to help prevent glucose excursions: “Basically it [closed-loop] does know what it's doing, but you've got that manual override if you need to, so I think… you definitely still need to have an element of knowing what you're doing as well, knowing… the bits that the [closed-loop]… doesn't know, so like your physical exercise, the food that you've just eaten and things like that.” (007) “I used Ease-off a lot at work, especially if I could see that my blood sugar was sitting just slightly lower and I knew that maybe I wasn't having lunch for like another two hours or something, to then just try and prevent a hypo.” (013)
Better collaboration with health care teams	Access to more detailed real-time data facilitates… better ad hoc clinical input: “I think it's a good thing that you can basically do a live feed to them, because it means that they've got up-to-date data that they can look at and very quickly change something if it needs to be changed. They're not looking at the five days prior, and you're saying well, now, you're having troubles now. And they're going: well, we can't see that data, so we can only go by what happened three days ago.” (019) … raises initial privacy concerns “It felt a bit Big Brother-ish at first, particularly when they would say: ‘oh well you had, you know, X number of carbs after 7 pm last Wednesday or something.” (015) …more personalised advice: “It's nice that somebody else can look at this data… they can see the graph of what's going on, how it's happening, how much insulin I've had, how much background insulin I've had. So just because they've got all that data, they can then tell me the exact thing that I need to do, which then sorts it out straightaway.” (020) … closer, more honest and trusting relationships with health care teams: “[It] allows me to communicate better, for them to understand better what I'm trying to say. And that communication, by being better, it builds trust… So I trust them more than if it was the opposite.” (002) “They have a little bit more trust in me, because they see my data and they see it's going well, so they understand my independency (sic), while maybe before they were a little bit more hesitating in giving me that independence.” (008)
Positive pregnancy experiences	Enjoying more normality and being able to work for longer: “Honestly, it allowed me to work. I would never be able… to work at the job that I was doing [waitressing] at all, if I didn't have the machine.” (002) “[Without the closed-loop] I wouldn't have gone out as much, and I wouldn't have done as much as what I done. I would have stopped work a lot more sooner than what I did…especially when you're self-employed, it does make a helluva lot of difference.” (018) Worrying less about their baby's development: “I didn't have that much fear for the pregnancy itself. And I think that's because of the closed-loop. So there are not that many concerns about the development of the- and the growth of the baby.” (007)