Research into the effects of epigenetic changes during pregnancy on the mother's long-term health is almost non-existent. This contrasts sharply with the wealth of attention paid to such cell-heritable changes, which alter gene activity but not DNA sequence, in the fetus and placenta as a developmental origin of health and disease (see S. S. Richardson Nature 512, 131–132; 2014).

The pregnant body undergoes huge changes: extensive tissue remodelling, expansion in blood volume by as much as 100%, immunological and metabolic alterations, and extensive shifts in hormone signalling. And complications such as gestational diabetes and pre-eclampsia, which both subside after giving birth, are known to increase the mother's risk of later developing type 2 diabetes (L. Bellamy et al. Lancet 373, 1773–1779; 2009) or hypertension and stroke (L. Bellamy et al. Br. Med. J. 335, 974; 2007). These all have big implications for public health.

We need to proceed cautiously when building causal narratives for health outcomes, and it might be hard to study epigenetic effects in mothers when few other results are available for comparison. But grant applications, hypotheses and experimental design should not be framed by the fetus alone.