Pregnancy is a crucial window of time that influences long-term population health. As a matter of justice, pregnant woman are entitled to high quality, evidenced-based care. As a matter of population health, we need to better understand foetal development, particularly the impact of lifestyle, stress, chronic conditions and clinical treatment during pregnancy. Pregnancy continues to be dominated by the precautionary principle, advocating for the routine exclusion of pregnant women from medical research, particularly intervention studies, on the grounds of foetal vulnerability. But this stance simply shifts the risk into the community. Due to a lack of evidence-based data, many pregnant women are refused medically important drugs, are subject to dangerous delays in getting drugs, or are prescribed drugs that are thought 'safe', despite evidence of possible teratogenicity. I argue that New Zealand needs to shift to a default position of inclusion of pregnant women in research; and to develop guidelines to facilitate their safe and responsible inclusion. The uniqueness of pregnancy gives rise to specific questions regarding research ethics. These questions warrant focused debate and the answers cannot simply be deduced from the general principles of research ethics we currently have in New Zealand.