PROBLEM: Pregnant women frequently experience psychological issues such as depression, anxiety, and excessive fear of childbirth. Non-pharmacological approaches for improving the mental health of pregnant women are increasingly needed in public health. BACKGROUND: Mindfulness-based interventions are among the most promising approaches to improving mental health. AIM: This study aimed to 1) develop a short online Japanese version of the mindfulness-based childbirth and parenting programme, and 2) investigate its effectiveness in improving mental health after intervention and birth. METHODS: A pre- and post-test study was conducted in Japan from February to October 2021 on a single group of 37 healthy pregnant women (16-34 gestational weeks). The four-week online mindfulness-based childbirth and parenting programme included psychoeducation based on mindfulness practices and the physiological processes of pregnancy and childbirth. Participants self-reported their evaluations of mindfulness, self-esteem, subjective happiness, sense of coherence, depression, stress, anxiety, and fear of childbirth before and after the programme (response rate: 97.4 %). The pre- and post-intervention responses were compared using a paired t-test. RESULTS: The results showed a significant reduction in perceived stress and fear of childbirth and an increase in mindfulness, self-esteem, and subjective happiness. No significant effects were observed in this low-risk population with regard to perinatal depression, anxiety, or sense of coherence. CONCLUSION: The newly developed condensed version of the mindfulness-based childbirth and parenting programme significantly improved maternal mental health. Further studies are required to clarify its effectiveness in larger and more diverse samples of pregnant women.