Table 3 Deductive themes and illustrative quotes (n = 10)

Theme 1—Language/wording: Participants indicated that non-judgemental wording around cannabis use as well as specific terms and context affected their choice to disclose their cannabis use while pregnant

“…say “cannabis” instead of marijuana, because I think of marijuana only being the plant… not edibles, or cbd and lip balm, or whatever.” -participant A

“Why you want to know is important. I would be way more up-front if I know it’s for research, than like, if they want to know at the hospital…” -participant F

“If someone sounds judgmental, that would make me not want to discuss it. If it’s something that it’s clear that they’re open to it, I would be like, yeah, here’s how I take it and why.” -participant D

“I wouldn’t say ‘use’, I would say ‘consume’. [use] has a bit of a negative to it.” -participant J

“[marijuana] sometimes has a negative connotation, like it’s a drug, but cannabis is more … like it’s natural.” -participant C

Theme 2a) Tool structure—General: The need for non-judgemental wording, and for cannabis to be treated separately from other substances on a questionnaire were identified as essential to avoid biased responses

“Say something at the beginning to make it clear that you’re not judging. If it sounds judgmental, or like, if I think you’re asking me so you can lecture me … someone’s judging me for using it, I wouldn’t answer.” -participant I

“I feel like if doctors were a little non-judgmental and a little less biased, then it would create some more honesty.” – participant C

“If it’s lumped in with, you know, smoking, then drinking, then marijuana, then …heroin and cocaine, that just gives it a real negative tone… like, it’s worse than alcohol, and almost as bad as heroin… I wouldn’t be answering, really, if it’s like that.” – participant E

“it makes more sense to me to have it with… supplements, or alternative therapies.”-participant B

Theme 2b) Tool structure—Response options: Allowing participants to indicate their reasons for consuming cannabis in pregnancy (which were predominantly reported as medicinal), was perceived as a key factor for encouraging honest disclosure. A response option indicating that use only took place prior to pregnancy recognition was also seen as essential to unbiased reporting

“I believe the stigma has died a lot. But there is still a big stigma with pregnancy for some people.” – participant A

“Especially in the first pregnancy women feel a lot more judged.”-participant H

“I don't believe it should be used in pregnancy to get stoned, or to get high. But I believe that if it's going to help with morning sickness, or relieve pain, or anything that you're going through that may cause you suffering or stress, I believe it safe to use…”- participant F

“some people stop as soon as they find out [they’re pregnant], so you need to be able to say that.”-participant G

Theme 3a) Patterns of use – Mode of consumption: Participants indicated numerous modes of consumption (vapour, oral/edible, topical, cannabidiol (CBD)) with varying doses for each, and some perceived as safer in pregnancy than others, supporting the need for standardized measurement of consumption-routes beyond smoking

“I would think that ingesting it… would be a lot safer [than smoking] because there's less transfer to the fetus.”-participant F

“I think edibles and lotions and liquid CBD capsules even, they're most likely more safe to take during pregnancy considering just that you're taking out the smoking out of the equation”-particpant G

“I don't necessarily think that smoking it is the smartest.”- participant B

“I mostly smoke, but I have drops and a lotion too.” – participant A

“… for vaping it, [I] stick to three puffs maximum when it comes to THC products.”- participant D

“Smoking does work quite quickly, especially for morning sickness. But a tincture can work…”-participant H

“I consume CBD oil daily, as well as smoking [cannabis].”-participant B

Theme 3b) Patterns of use – Frequency and Timing: Participants consistently indicated their patterns of use changed during pregnancy to a more frequent consumption of smaller amounts, compared to their general use pre-pregnancy, indicating that tool response options need to include high frequencies (i.e. multiple times per day) and small dose-per-use categories, compared to existing survey questions

“I use it different (sic) now that I’m pregnant… I have a quick drag whenever I need it, so 3 or 4 times a day sometimes, but just a tiny bit, instead of having a lot at once.”-particpant C

“…I resumed micro-dosing daily…” -participant E

“I think asking about frequency makes sense—most people use it pretty regular (sic)” -participant J

Theme 3b) Patterns of use – Dose: Amounts of cannabis typically consumed at each sitting was discussed primarily in subjective terms (i.e. large, small), perceptions of which may vary considerably between consumers, and identifying the weights or exact doses used at each sitting was perceived as difficult or infeasible, particularly for dried cannabis. Comparison measures were preferred

“I know how much I buy by weight, but I couldn’t tell you the grams I put in the pipe yesterday evening…”-particpant F

“With smoking it, it’s harder… like, a big joint for me might not be big for my sister.”-participant G

“It’s easy if it’s an edible, because it tells you on the label…”-particpant A

“The THC oil that I have is 30 mg per mil, so that would work out to being about point three milligrams for point one or point two of a milliliter.”-participant E

“Maybe start at half a milliliter, so that would be what? More like 10 mg, I guess, of the 40 mg [per milliliter] stuff that I have.”-particpant B

“I would say the easiest way for people to say how much they smoke would be like a pea-sized amount, or a grape-size…compare it to something. Then you could figure out the grams from that. I don’t know how many grams or milligrams I use every time.”-particpant C

“I might use a small dab like the size of a dime, or other times it might be like twice as much…”-participant D