Bydlowski has proposed that pregnant women show an altered mental state, qualified as ‘psychic transparency’, characterized by a lowering of the usual defenses against the repressed unconscious and the parallel surfacing of (infantile) reminiscences, fantasies and representations. This state of highly invested mental work is thought to be characterized by a predominance of primary process mentation. The Geo-Cat, a simple non-linguistic instrument for the probing of primary and secondary processes, revealed a substantial increase in primary process mentation in pregnant women compared with control groups (n = 118 pregnant women from their 6th to their last month of pregnancy, n = 81 nonpregnant control women, n = 78 future fathers, and n = 40 control men). This difference remained highly significant after factoring out the influence of confounding variables. Also, this increase was not different between women giving birth for the first time, and women, having a second or subsequent child. For all these reasons, we are drawn to think that it is the mere event of having another being growing inside one’s own body, which, by requiring huge mobilization of mental energy, dries up the mental sources required to maintain the usual defenses. As a consequence, primary process mentation would be at work, resulting in a so-called ‘psychic transparency’ state. This mental explanation is an alternative for a mere biological and deficit interpretation, as it allows us to consider the function of this state, both for the mother-to-be and for the mother-infant bond.