Obstetric ultrasound has become a significant tool in obstetric practice, however, it has been argued that its increasing use may have adverse implications for women's reproductive freedom. This study aimed to explore Australian obstetricians' experiences and views of the use of obstetric ultrasound both in relation to clinical management of complicated pregnancy, and in situations where maternal and fetal health interests conflict.A qualitative study was undertaken as part of the CROss-Country Ultrasound Study (CROCUS). Interviews were held in November 2012 with 14 obstetricians working in obstetric care in Victoria, Australia. Data were analysed using qualitative content analysis.One overall theme emerged from the analyses: The ethical challenge of balancing maternal and fetal health interests, built on four categories: First, Encountering maternal altruism' described how pregnant women's often 'altruistic' position in relation to the health and wellbeing of the fetus could create ethical challenges in obstetric management, particularly with an increasing imbalance between fetal benefits and maternal harms. Second, 'Facing shifting attitudes due to visualisation and medico-technical advances' illuminated views that ultrasound and other advances in care have contributed to a shift in what weight to give maternal versus fetal welfare, with increasing attention directed to the fetus. Third, 'Guiding expectant parents in decision-making' described the difficult task of facilitating informed decision-making in situations where maternal and fetal health interests were not aligned, or in situations characterised by uncertainty. Fourth, 'Separating private from professional views' illuminated divergent views on when the fetus can be regarded as a person. The narratives indicated that the fetus acquired more consideration in decision-making the further the gestation progressed. However, there was universal agreement that obstetricians could never act on fetal grounds without the pregnant woman's consent.This study suggests that medico-technical advances such as ultrasound have set the scene for increasing ethical dilemmas in obstetric practice. The obstetricians interviewed had experienced a shift in previously accepted views about what weight to give maternal versus fetal welfare. As fetal diagnostics and treatment continue to advance, how best to protect pregnant women's right to autonomy requires careful consideration and further investigation.