For pregnant women with a known cardiac condition or those who develop cardiac disease during pregnancy, there is an increased risk of complications during pregnancy, to both mother and foetus. To reduce this risk, best practice guidelines have been developed and available in South Australia for several years. Measuring clinical practice against the guideline recommendations verifies real-life practice and an essential part of any clinical practice quality improvement project by identifying gaps. This study is the first report on adherence to statewide perinatal guidelines for these women in South Australia. To evaluate adherence to evidence-based clinical practice perinatal guidelinesTo identify predictors of adherence.Make comparisons across three practice settings examined. A retrospective cross-sectional observational design that analysed data from medical records. Three SA Health public metropolitan, university-affiliated teaching hospitals with an obstetric service within a ten-year timeframe (2003-2013). 271 admissions of women who were categorised as 'pre-existent' or 'newly acquired' cardiac condition during their pregnancy. Adherence to guidelines was measured using a purposefully designed scoring system across the three sites. The researcher chose a minimum acceptable score of 17 applicable to the 'newly acquired' group and 35 for the 'pre-existent' group. Overall adherence to the perinatal guidelines for the combined groups (n = 271) reported a mean score of 16.3, SD ± 6.7, with a median score of 17. Women in the 'newly acquired' group scored less compared to women in the 'pre-existent' group (Estimate -2.3, CI -3.9,-0.7). Variance in adherence was observed across the three hospitals (P value <0.0001). The most significant predictor of adherence to guidelines was pre-pregnancy cardiac consultation which increased the likelihood of preconception care by Odds ratio 18.5 (95%, CI 2, 168). Similarly, compliance with mental health screening was associated with improved adherence to antenatal assessments (OR: 11.3(95% CI 4.7, 27.3). There was overall suboptimal adherence to the statewide guidelines for women with cardiac conditions in pregnancy. The variance in the level of adherence across the three hospitals correlated with the exposure to higher acuity cases, and that appropriate up- referral to a higher acuity hospital was intrinsically linked to better adherence. Recommendations include preconception counselling, and to ensure that all health practitioners have the skills, sufficient training and time to complete a comprehensive initial antenatal assessment. ACTRN12617000417381.