High Body Mass Index is associated with an expansion of endometrial T Regulatory cell and macrophage populations.

Obesity is associated with implantation failure, miscarriage, low-grade inflammation and a reduction in peripheral immune-suppressive T regulatory (Treg) cells. Therefore, we postulated that this reduction may also extend to the endometrium and cause embryonic loss. In a cohort of 40 infertile women, without implantation failure or recurrent miscarriage, we examined the density of Treg cells, macrophages and natural killer (NK) cells in mid-luteal endometrial biopsies. Significant positive correlations were observed between BMI and endometrial Treg cells and macrophages, but no relationship with NK cells. We postulate that this change may be a positive adaption to minimise adiposity related inflammation.