During his first week in office, US President Donald J Trump issued a presidential memorandum to reinstate and broaden the reach of the Mexico City policy. The Mexico City policy (which was in place from 1985-1993, 1999-2000 and 2001-2009) barred foreign non-governmental organisations (NGOs) that received US government family planning (FP) assistance from using US funds or their own funds for performing, providing counselling, referring or advocating for safe abortions as a method of FP. The renamed policy, Protecting Life in Global Health Assistance (PLGHA), expands the Mexico City policy by applying it to most US global health assistance. Thus, foreign NGOs receiving US global health assistance of nearly any type must agree to the policy, regardless of whether they work in reproductive health. This article summarises academic and grey literature on the impact of previous iterations of the Mexico City policy, and initial research on impacts of the expanded policy. It builds on this analysis to propose a hypothesis regarding the potential impact of PLGHA on health systems. Because PLGHA applies to much more funding than it did in its previous iterations, and because health services have generally become more integrated in the past decade, we hypothesise that the health systems impacts of PLGHA could be significant. We present this hypothesis as a tool that may be useful to others' and to our own research on the impact of PLGHA and similar exogenous overseas development assistance policy changes.