There are three Gunas present in our body- Sattva, Rajas and Tamas.

When we do some physical exercise or yog it helps us to reduce Tamas in our body. Tamas is connected with negative thoughts, impurities, laziness over thoughts and disturbed sleep or over sleep which we cannot afford during pregnancy. So mother should engage herself in good scientific physical health programs for the betterment of the womb child.