An obesity-associated increase in inflammatory markers has been observed in pregnant women as early as first trimester46 and could thus be another potential factor for regulation of ABCB1/P-gp expression, although current data from the literature is not consistent in determining if the most likely result is an up- or a down-regulation of ABCB1/P-gp and ABCG2/BCRP with increasing maternal inflammation. Here, ABCG2 is linked to obesity due to melanocortin 4 receptor deficiency.