It is now widely accepted – in principle, if not always in practice – by researchers, research sponsors, research ethics committees and research regulators, that research involving children and research involving women benefits children and women, respectively. This is not yet the case for research involving pregnant women, but we expect that it will soon be so, given the validity and weight of the arguments in support of such research. When this day comes, a number of practical ethical issues will come to the fore, including issues of trial design, risk perception in prospective participants’ assessments of the harm–benefit ratio, informed consent, the right to withdraw, liability and indemnification.