The number of male pups within a litter of NMRI mice is associated with the dam's food preferences late in pregnancy.

Pregnancy related differences in food preferences and food intake are well recognized in animals and humans. Changes in maternal hormonal profiles are supposed to be implicated in such a phenomenon. Since fetal sex hormones are excreted in their dams' bloodstream, they can affect the behaviour of mothers during gestation. We investigated whether there was a relationship between the number of male pups within the litter and food preferences in pregnant mice. In the first experiment we found that, parcelling out the effect of litter size, the number of male fetuses was positively correlated to maternal testosterone levels on pregnancy day (PD)18. In the second experiment we showed an association between the number of males and the consumption of a 0.25% saccharin solution on PD18, controlling for litter size and baseline (before pregnancy) saccharin intake. In the third experiment, mice on PD18 were placed in a test cage and underwent a 1-h binary choice test between two unknown unpalatable diets, a high fat diet (HFD) and a sweet mesh diet (HSD). Results revealed that the number of males was negatively associated with the preference for the HFD at birth. These results are consistent with the hypothesis that the behavioural profile of dams can be associated with fetal gender composition.