But what we found when we tested them on very faint substances is that they perform just as well as the control group, but they reacted very strongly to the smells when they were there.

So it was not about being able to smell smells that they couldn't smell before, but they reacted completely different. So it was more on a reactivity level, and that is thought to be protective of the child.

— Jonas Olofsson, professor of psychology at Stockholm University and director of the Sensory Cognitive Interaction Lab, on his research on pregnant women, from the transcript of the radio broadcast Week of Wonder: 'Vivaldi smells like breakfast sausage' at WBUR.