Scientists have made a surprising finding when studying the impact of exercise during pregnancy in rats. They have compared two types of mothers: ones that had exercise wheals inside their cage, and others which did not and which were prevented to be too active.

Gerd Kempermann of the Max Delbrück Center for Molecular Medicine in Berlin and his colleagues have found that, at first, the babies from the mothers that exercised during pregnancy had less body weight than the others. However, around a month later they have made up for it and more: they have developed around 40% more cells in the hippocampus, the area of the brain vital for learning and memory.

Scientists assume that the extra cells in the hippocampus indicate that the pups had a greater intelligence. However, they couldn't actually verify this assumption via behavioral tests because the mice were sacrificed in order to examine their brains. "We'd have to replicate the experiment, and that would take two years," said Kempermann.

Other previous studies have shown that adults with increased activity also develop supplementary cells in the hippocampus themselves. "Now, we've established that it seems to be transmissible to offspring," Kempermann said.

The reason for this connection might be that, besides the fact that activity is generally beneficial, it is also an indication that the rodents are more likely to encounter novel situations which demand extra intelligence and memory.

Kempermann said that the results of his study do not apply to people but that they point out that "we should have another look at human sport and exercise during pregnancy".