Obesity is associated with a reduction in fertility treatment success and increased risks to mother and child. Therefore guidelines of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) suggest that a body mass index exceeding 35 kg/m2 should be an absolute contraindication to assisted fertility treatment such as in vitro fertilisation IVF. In this paper we challenge the ethical and scientific basis for such a ban. Livebirth rates for severely obese women are reduced by up to 30%, but this result is still far better than that observed for many older women who are allowed access to IVF. This prohibition is particularly unjust when IVF is the only treatment capable of producing a pregnancy, such as bilateral tubal blockage or severe male factor infertility. Furthermore, the absolute magnitude of risks to mother or child is relatively small, and while a woman has a right to be educated about these risks, she alone should be allowed to make a decision on proceeding with treatment. We do not prohibit adults from engaging in dangerous sports, nor do we force parents to vaccinate their children, despite the risks. Similarly, we should not prohibit obese women from becoming parents because of increased risk to themselves or their child. Finally, prohibiting obese women’s access to IVF to prevent potential harms such as ‘fetal programing’ is questionable, especially when compared to that child never being born at all. As such, we believe the RANZCOG ban on severely obese women’s access to assisted reproductive treatment is unwarranted and should be revised.