Background: Rheumatic heart disease (RHD) poses significant perinatal risks. We aimed to describe the spectrum, severity and outcomes of rheumatic mitral valve disease in pregnancy in Australia and New Zealand. Methods: A prospective, population-based cohort study of pregnant women with RHD recruited 2013–14 through the hospital-based Australasian Maternity Outcomes Surveillance System. Outcome measures included maternal and perinatal morbidity and mortality. Univariable and multivariable logistic regression analyses were undertaken to test for predictors of adverse maternal and perinatal outcomes. Results: Of 274 pregnant women identified with RHD, 124 (45.3%) had mitral stenosis (MS) and 150 (54.7%) had isolated mitral regurgitation (MR). One woman with mild MS/moderate MR died. There were six (2.2%) stillbirths and two (0.7%) neonatal deaths. Babies born to women with MS were twice as likely to be small-for-gestational-age (22.7% vs 11.4%, p=0.013). In women with MS, use of cardiac medication (AOR 7.42) and having severe stenosis (AOR 16.35) were independently associated with adverse cardiac outcomes, while NYHA class >1 (AOR 3.94) was an independent predictor of adverse perinatal events. In women with isolated MR, use of cardiac medications (AOR 7.03) and use of anticoagulants (AOR 6.05) were independently associated with adverse cardiac outcomes. Conclusions: Careful monitoring and specialist care for women with RHD in pregnancy is required, particularly for women with severe MS, those on cardiac medication, and those on anticoagulation, as these are associated with increased risk of adverse maternal cardiac outcomes. In the context of pregnancy, contraception and preconception planning are important for young women diagnosed with RHD.