Pregnancy Exercise Benefits: More Evidence

Light exercise during pregnancy may improve the future health of a child by controlling weight in the womb, New Zealand and US researchers say.

Overweight or obese mums are more likely to have larger babies which could be at higher risk of health problems later in life. There is increasing evidence that the future metabolism of a child may be influenced by its environment in the womb, and that babies who are relatively heavy for their length may be more likely to be obese in future years.
According to the source, on average, the exercising women had babies who were no shorter than their non-exercising counterparts, but who were 0.32 lb (143 grams) lighter on average. 

Source: please read articles at bbc.co.uk and The Journal of Clinical Endocrinology and Metabolism