Pregnancy reduces the perception of anxiety.

In humans, stress can be contagiously transmitted via chemosignals on a subconscious level. This study investigates how pregnancy affects neural responses to anxiety chemosignals. Using cotton pads, 28 men donated axillary sweat immediately before an academic examination (anxiety sweat) and during ergometer training (control). Via a constant-flow olfactometer, samples were presented (oddball paradigm) to 12 non-pregnant (NP) women, 14 women in their first (T1), and 18 in their third (T3) trimester of pregnancy. Chemosensory event-related potentials and current source densities (CSD) were analysed (60 electrode setup). Compared to NP-women, pregnant women display diminished evaluative processing of the sweat samples (targets; P3-1/ P3-2 amplitudes) and delayed evaluative processing of the anxiety sweat (targets; P3-2 latency). T3-women show attenuated early processing (targets; N1 amplitude) compared to NP-women, and reduced evaluative processing compared to T1-women (standards; P3-2 amplitude). CSDs (P3-1/ P3-2 latency ranges) reveal that T1- and T3-women show an atypical activation distribution to anxiety sweat. Most participants were unable to detect the sweat samples (anxiety sweat: 79.5%, sport sweat 88.6%). The results demonstrate that the processing of anxiety chemosignals progressively vanishes during pregnancy. This effect is likely to occur without any cognitive control.