BackgroundPre-existing diabetes mellitus (DM) is a challenging pregnancy complication as poor glycemic control is associated with adverse maternal and fetal outcomes. In this study, we aimed to investigate DM-related knowledge, attitudes, preconception care practices, and contraceptive prevalence in women with DM.MethodsThis descriptive cross-sectional survey was conducted among reproductive-aged Thai women receiving DM treatment at King Chulalongkorn Memorial Hospital between August 1, 2021, and June 30, 2022. Patients with DM who were not pregnant or trying to conceive and could be contacted via the phone were included and a validated self-administered questionnaire was distributed electronically.ResultsA total of 238 participants were included in the final analysis, yielding 69.4% response rates. The mean (standard deviation) score for knowledge of pregnancy planning and pregnancy-related risks was 6.8 (3.5) out of 15. Only about half of the participants had discussed pregnancy planning with their physicians. Multivariable analysis showed that younger age at DM diagnosis, non-Buddhism, married, higher education, and medical personnel were significantly associated with higher knowledge scores. Women aged > 45 years and those with higher practice scores had significantly higher adjusted odds of using highly effective contraception; the most common methods included male condoms and combined oral contraceptive pills. There was an unmet need for contraception in 9.5% of women with DM.ConclusionsAlthough highly effective contraception is safe for patients with DM, only about half of our participants used tier one or two contraceptives or had received consultation regarding preconception planning. There was a notable gap in care coordination among specialists; integrating reproductive healthcare into DM therapy would improve access to preconception care.